Focus On Science Grade 8 (Teacher's Guide)

8 Active-learning approach Contextual learning 21st Century Learning Skills Hands-on activities Constructivist approach Consulting author Giam Kah How TEACHER’S GUIDE SCIENCE FOCUS-ON ©Praxis Publishing_Focus On Science

CONTENTS Introduction iii Developing an Understanding of Scientific Concepts and Theories iii Developing Scientific and Thinking Skills vi • Inquiry-based Learning vi • Constructivism vii • Contextual Learning vii • Higher-Order Thinking Skills (HOTS) vii • 21st Century Skills viii • STEM/Projects ix Developing Scientific Attitudes and Noble Values ix How to Use the Focus-on Science Series xi Scoring Rubric for Affective Domain xiii Scoring Rubric for Scientific Thinking xiv Scoring Rubric for STEM Activities/Projects xv Scheme of Work xvi Introduction to Cells 1 Lesson 1.1 Cells and Microscopes 2 Lesson 1.2 Animal and Plant Cells 4 Lesson 1.3 Unicellular and Multicellular Organisms, and Cell Specialisation 8 Structures and Functions of the Human Body Systems 12 Lesson 2.1 Food and Digestive System 13 Lesson 2.2 Circulatory System 22 Lesson 2.3 Respiratory System 27 Lesson 2.4 Excretory System 30 Work, Energy and Simple Machines 35 Lesson 3.1 Work 36 Lesson 3.2 Power 37 Lesson 3.3 Sources and Forms of Energy 39 Lesson 3.4 Simple Machines 44 Vibrations, Waves and Light 51 Lesson 4.1 Vibrations 52 Lesson 4.2 Waves 53 Lesson 4.3 Light and Optical Instruments 59 Elements, Compounds and Mixtures 69 Lesson 5.1 Atoms and Molecules 70 Lesson 5.2 Elements 72 Lesson 5.3 Compounds 75 Lesson 5.4 Mixtures 78 CHAPTER 1 CHAPTER 2 CHAPTER 3 CHAPTER 4 CHAPTER 5 Teacher’s Guide Focus-on Science Grade 8 i © Praxis Publishing Singapore Pte. Ltd. ©Praxis Publishing_Focus On Science

Acids and Alkalis 84 Lesson 6.1 Acids and Alkalis 85 Lesson 6.2 Neutralisation 92 Structure of the Earth and Natural Disasters 96 Lesson 7.1 Structure of Earth 97 Lesson 7.2 Movement of Tectonic Plates 100 Lesson 7.3 Earthquakes 101 Lesson 7.4 Volcanoes 104 CHAPTER 6 CHAPTER 7 Teacher’s Guide Focus-on Science Grade 8 ii © Praxis Publishing Singapore Pte. Ltd. ©Praxis Publishing_Focus On Science

Introduction The Focus-on Science Series is designed to support the teaching of science in lower secondary schools by making science learning more engaging for students. The theoretical framework of this series is based on the understanding that science is a body of knowledge and skills that provides an understanding of nature. It is also to nurture curiosity and creativity. This series aims to support the learning of science by focusing on three main objectives: 1. Developing an understanding of scientific concepts and theories 2. Developing scientific and thinking skills 3. Developing scientific attitudes and noble values Developing an Understanding of Scientific Concepts and Theories Scientists have been collecting data, facts and ideas for centuries. From the data, scientists have formulated concepts, principles and theories. This knowledge of science is the product of science. The content in this series sets out the scientific knowledge, facts and ideas that students need to understand. The contents of the series are written to ensure students are able to achieve all the learning goals outlined in the lower secondary science curriculum as follows. At the end of phase D: 1. Students can classify living things and objects based on their observed characteristics, identify the properties and characteristics of substances, differentiate between physical and chemical changes, and separate simple mixtures. 2. Students can describe atoms and compounds as the smallest units of matter, and cells as the smallest units that make up living things. They can identify the organisation of living things and analyse the connections between organ systems and their functions, including abnormalities or disorders that may occur in specific organ systems, such as digestive system, circulatory system, respiratory system and reproductive system. They can also explain the interactions between living things and their environment, develop strategies to prevent and mitigate pollution and address issues related to climate change. Additionally, they are encouraged to explore the concept of inheritance and learn about the practical applications of biotechnology in everyday life. 3. Students are able to measure various physical quantities they encounter and explore different types of motion and forces. They develop an understanding of the relationship between work and energy, measure temperature changes caused by transfer of heat energy, and differentiate between insulators and conductors of heat. 4. Students have a clear understanding of motion, force and pressure, including basic principles of simple machines. They also comprehend vibrations and waves, as well as the characteristics of light, such as reflection and refraction. Furthermore, they are familiar with simple optical tools commonly used in daily life. 5. Students can construct basic electrical circuits and understand the relationship between magnetism and electricity. They can apply this knowledge to solve everyday challenges and problems. Teacher’s Guide Focus-on Science Grade 8 iii © Praxis Publishing Singapore Pte. Ltd. ©Praxis Publishing_Focus On Science

6. Students can explain the relative position of the Earth-Moon-Sun in the Solar System and comprehend the structure of the Earth’s layers. This knowledge enables them to understand deeper natural phenomena and play their roles in disaster mitigation. 7. Students recognise pH as a measure of substance acidity or alkalinity, and utilise it to classify materials based on their pH as acids or bases. With this understanding, students identify the physical and chemical properties of soil and their relationship to organisms and environmental conservation. 8. Students demonstrate the determination to make decisions and avoid harmful additives and addictive substances that can negatively impact both themselves and the environment. Each grade contains a specified and detailed list of lessons based on the learning goals outlined in phase D. Grade 7 Grade 8 Grade 9 Chapter 1 Science and Measurements 1.1 What is Science? 1.2 Science Laboratory 1.3 Measurements 1.4 Measuring Tools Chapter 1 Introduction to Cells 1.1 Cells and Microscopes 1.2 Animal and Plant Cells 1.3 Unicellular and Multicellular Organisms, and Cell Specialisation Chapter 1 Human Reproductive System 1.1 Cell Division 1.2 Human Reproductive System 1.3 Puberty 1.4 Menstrual Cycle 1.5 Fertilisation 1.6 Pregnancy 1.7 Common Disorders and Diseases of the Male and Female Reproductive Systems 1.8 Lifestyle Factors that Support the Reproductive System Chapter 2 Matter 2.1 States of Matter 2.2 Physical and Chemical Changes 2.3 Density Chapter 2 Structures and Functions of the Human Body Systems 2.1 Food and Digestive System 2.2 Circulatory System 2.3 Respiratory System 2.4 Excretory System Chapter 2 Reproduction in Animals and Plants 2.1 Sexual Reproduction in Animals 2.2 Asexual Reproduction in Animals 2.3 Sexual Reproduction in Flowering Plants 2.4 Pollination 2.5 The Development of Fruits and Seeds in Plants 2.6 Seed Dispersal 2.7 Germination of Seeds 2.8 Reproduction of Ferns, Mosses and Conifers 2.9 Asexual Reproduction in Plants 2.10 The Use of Reproductive Technologies Teacher’s Guide Focus-on Science Grade 8 iv © Praxis Publishing Singapore Pte. Ltd. ©Praxis Publishing_Focus On Science

Grade 7 Grade 8 Grade 9 Chapter 3 Temperature and Heat 3.1 Temperature and Scale 3.2 Thermometers 3.3 Expansion and Contraction of Matter 3.4 Heat Capacity 3.5 Heat Transfer 3.6 Heat Conductors and Heat Insulators 3.7 How Types of Surfaces Affect Heat Absorption and Emission 3.8 Body Temperature Regulation Chapter 3 Work, Energy and Simple Machines 3.1 Work 3.2 Power 3.3 Sources and Forms of Energy 3.4 Simple Machines Chapter 3 Inheritance 3.1 Genetic Material 3.2 Inheritance of Traits 3.3 Laws of Inheritance 3.4 Inheritance in Humans 3.5 Genetic Disorders 3.6 Selective Breeding 3.7 Adaptations and Natural Selection Chapter 4 Motion and Force 4.1 Motion 4.2 Force and Motion Chapter 4 Vibrations, Waves and Light 4.1 Vibrations 4.2 Waves 4.3 Light and Optical Instruments Chapter 4 Biotechnology 4.1 What is Biotechnology? 4.2 Applications of Biotechnology and its Importance Chapter 5 Living Things 5.1 Biodiversity 5.2 Living and Non-living Things 5.3 Classification of Living Things Chapter 5 Elements, Compounds and Mixtures 5.1 Atoms and Molecules 5.2 Elements 5.3 Compounds 5.4 Mixtures Chapter 5 Electricity 5.1 Electric Field and Electric Potential Difference 5.2 Electric Circuits 5.3 Electric Current, Potential Difference and Resistance 5.4 Series and Parallel Circuits 5.5 Electrical Energy and Electrical Power 5.6 Using Electricity Safely at Home Chapter 6 Interactions Among Organisms and the Environment 6.1 Biotic and Abiotic Components 6.2 Food Chains and Food Webs 6.3 Nutrient Cycles in an Ecosystem 6.4 Interactions between Organisms 6.5 Factors that Affect the Organisms and Environment Chapter 6 Acids and Alkalis 6.1 Acids and Alkalis 6.2 Neutralisation Chapter 6 Magnetism and Electromagnetism 6.1 Magnets and Magnetism 6.2 Electromagnetism and Lorentz Force 6.3 Electromagnetic Induction 6.4 Transformers 6.5 Applications of Magnetism Chapter 7 Earth and the Solar System 7.1 The Solar System 7.2 Earth and Its Satellite Chapter 7 Structure of the Earth and Natural Disasters 7.1 Structure of Earth 7.2 Movement of Tectonic Plates Chapter 7 Pressure 7.1 Pressure 7.2 Pressure in Liquids 7.3 Gas Pressure Teacher’s Guide Focus-on Science Grade 8 v © Praxis Publishing Singapore Pte. Ltd. ©Praxis Publishing_Focus On Science

Grade 7 Grade 8 Grade 9 7.3 The Sun 7.3 Earthquakes 7.4 Volcanoes 7.4 Pascal’s Principle 7.5 Archimedes’ Principle 7.6 Bernoulli’s Principle 7.7 Osmosis and Osmotic Pressure 7.8 Applications of Pressure in Organisms Chapter 8 Soil 8.1 What is Soil? 8.2 Properties of Soil 8.3 Roles of Soil and Soil Organisms 8.4 Soil Formation 8.5 Conservation of Soil Developing Scientific and Thinking Skills The series promotes the inquiry-based learning method that adopts constructivist and contextual approaches to enable students to master science process skills and manipulative skills. This series also provides activities that develop higher-order thinking skills and the 21st century skills of students in their learning. Inquiry-based Learning Inquirybased Inquiry-based learning is a form of active learning that begins by posing questions, problems or situations, rather than simply presenting established facts and knowledge. In the classroom, students play an active role. They are empowered to pose questions, explore situations, gather information, solve problems, find solutions and communicate their results. They learn more by looking for an answer to a question. In addition, teachers may start with guided inquiry to build up background knowledge of the topic before letting the students take a role in developing their own inquiry. When carrying out inquiry-based activities, students work like scientists and acquire capabilities they need in their future lives. The key to effective scientific inquiry is to master scientific skills which are required to investigate and understand nature, to find solutions to problems and to make decisions in a systematic manner. Scientific skills comprise science process skills and manipulative skills. Science process skills are designed to provide a foundation for the mastering of science concepts and the development of thinking skills needed in the 21st century, while manipulative skills are the skills where students use basic tools in the learning of science. The mastering of science process skills together with scientific attitudes and appropriate knowledge ensure students’ ability to think effectively. The six basic science process skills that form the foundation of science lessons are: • Observation • Communication • Classification • Measurement • Inference • Prediction Teacher’s Guide Focus-on Science Grade 8 vi © Praxis Publishing Singapore Pte. Ltd. ©Praxis Publishing_Focus On Science

Constructivism Constructivism Constructivism helps students understand science better. Students are active learners. They construct their own understanding and knowledge of the world by reflecting on their personal experiences and by relating the new knowledge to what they have already learned. In the classroom, the focus tends to shift from the teacher to students. Teachers prepare students for lifelong learning. Students enjoy learning more when they are active participants rather than passive recipients of information. For example, a group of students are discussing a problem in science. The teacher focuses on helping them to restate their questions in useful ways even though he/she knows the “answer” to the problem. The teacher prompts the students to test their prior knowledge. The teacher lets the students explore and come up with relevant concepts. Constructivism focuses on learning how to think and understand. Students learn to question things and apply their curiosity to the world. Students communicate with others and share their understanding, knowledge and experience to come up with new knowledge. Contextual learning Contextual Contextual learning helps students to apply new knowledge and skills to real-life situations. Learning is relevant and meaningful when students can apply what they learn in the classroom to their daily life. Teachers can provide a lot of hands-on activities that help students to connect the content of knowledge to application. Students also learn from others through teamwork, discussions, cooperation and selfreflection. Some examples of contextual teaching and learning strategies include: • Using multiple contexts Learning experiences are enriched when students learn skills in multiple contexts such as school, community and family. • Problem-based Learning can begin with a simulated or real problem. Students use critical thinking skills to address and resolve the problem. • Encouraging self-learning Students are lifelong learners who seek out, analyse and use information with little to no supervision. Higher-Order Thinking Skills (HOTS) HOTS Higher-Order Thinking Skills (HOTS) is a concept of education reform that is mainly based on Bloom’s Taxonomy. The levels of thinking in Bloom’s Taxonomy, starting from the lowest to the highest are remembering, understanding, applying, analysing, evaluating and creating. When we talk about HOTS, we are concentrating on the highest four levels, namely, applying, analysing, evaluating and creating. Higher-Order Thinking Skills are activated when students encounter unfamiliar problems, questions or dilemmas. When they apply these skills, they can give explanations, make decisions and produce products that are valid within the context of available knowledge and experience. Appropriate teaching strategies and learning environment help students develop HOTS where they learn how to be self-directed, self-disciplined and self-monitored in their thinking process. Teacher’s Guide Focus-on Science Grade 8 vii © Praxis Publishing Singapore Pte. Ltd. ©Praxis Publishing_Focus On Science

Higher-Order Thinking Skills (HOTS) Lower-Order Thinking Skills (LOTS) Producing an original work Constructing, developing, designing, modifying Justifying a decision Judging, defending, evaluating, concluding Drawing connections among ideas Relating, organising, comparing, differentiating Using information in new situations Solving, predicting, demonstrating, applying Explaining ideas or concepts Summarising, classifying, discussing, identifying Recalling facts and basic concepts Recognising, listing, stating, defining BLOOM’S TAXONOMY CREATING EVALUATING ANALYSING APPLYING UNDERSTANDING REMEMBERING Source: Armstrong, Patricia. “Bloom’s Taxonomy”. Center for Teaching, Vanderbilt University, https://cft.vanderbilt.edu/guides-sub-pages/blooms-taxonomy/ Projects and activities should cover questions that challenge students to clarify their understanding, come up with reasons and pieces of evidence for their thinking, define their views and perspectives, determine consequences and evaluate concepts. Some ideas or activities that promote Higher-Order Thinking Skills are given below: • Applying – Predicting Given the weather report, students could be asked to predict the weather for the next day. • Analysing – Distinguishing Given a list of plant names, students could be asked to distinguish between the flowering plants and the non-flowering plants. • Evaluating – Judging Given some types of materials, students could be asked to judge them to identify which is the best conductor of heat. • Creating – Constructing Students could be asked to construct a model of a submarine. 21st Century Skills 21st Century skills The series is written to help teachers play their roles as facilitators of thinking and reasoning skills. 21st Century Skills are needed by students in order to succeed in the information age. Students should acquire these skills as they complement the science process skills. The 21st Century Skills include: • Critical thinking and problem-solving skills • Interpersonal and self-reliance skills • Information and communication skills Teacher’s Guide Focus-on Science Grade 8 viii © Praxis Publishing Singapore Pte. Ltd. ©Praxis Publishing_Focus On Science

21st Century Skills can be practiced in the learning of science. Examples include: • Communication Students express their ideas and information in words, sounds and images in order to build shared understanding. • Integrating technology Students can apply computer and technology skills to learn and solve problems. Students possess the ability to learn quickly, process information accurately and use information in decision-making. STEM/Projects STEM Students can apply 21st Century skills in STEM activities or projects. STEM stands for science, technology, engineering and mathematics. STEM develops a set of thinking, creative reasoning, teamwork and investigative skills that students can use in their daily lives. A summary of the STEM acronym is as below: Science Focuses on the understanding of our environment, exploring and investigating the world using scientific skills, and critical and creative thinking skills. Technology Focuses on investigations using computers, tools and software applications. Engineering Focuses on solving problems using varied materials and designing, creating and building things that work. Mathematics Focuses on numbers and counting, space, sizes, shapes, measurements and patterns. Some examples of ideas for STEM project-based learning activities are given below: • Creating Earth’s model Students can create a model of the Earth using materials, such as clay, playdough and mashed paper. They can do all the steps by themselves and play a role in their learning. • Creating a hand pollinator Students learn to design, create and test a hand pollinator to transfer pollen grains from one flower to another. The STEM/Project-based activities aim to provide students the opportunities to work in small groups, search for information using technology, be critical in their judgment and decision making, create the endproduct and share with their peers to meet the needs of becoming the 21st century learners. By doing the projects, students explore themes and important issues such as climate change, health, technology and ethical issues of stem cell research. Through this process, students can take real action in addressing these issues based on their stages of learning, individual needs and contribute to their surrounding environment. Developing Scientific Attitudes and Noble Values Scientific attitudes and noble values can be inculcated through science activities. Students will have an interest and curiosity about their surroundings. They will develop an awareness of their responsibility to care for the environment. They learn to be systematic in carrying out activities, to be honest and Teacher’s Guide Focus-on Science Grade 8 ix © Praxis Publishing Singapore Pte. Ltd. ©Praxis Publishing_Focus On Science

accurate in recording their observations or data. Examples of scientific attitudes and noble values that are important in the learning of science are: • Being responsible about the safety of oneself, others and the environment • Realising that science is a means to understand nature • Appreciating the contribution of science and technology • Appreciating and practicing clean and healthy living • Appreciating the balance of nature • Having critical and analytical thinking • Being respectful and well-mannered • Being confident and independent • Being thankful to God • Thinking rationally • Being cooperative • Being objective • Being flexible • Being caring • Daring to try Proper planning is required for effective inculcation of scientific attitudes and noble values during science lessons. Teachers should ensure that students carry out science activities in a careful, cooperative and honest manner during the lessons. Teacher’s Guide Focus-on Science Grade 8 x © Praxis Publishing Singapore Pte. Ltd. ©Praxis Publishing_Focus On Science

How to Use the Focus-on Science Series The series is written to cater for the needs of lower secondary school students in developing scientific knowledge, skills, attitudes and noble values. The series provides key scientific information that makes the learning of science inquiry-based in order to develop scientific thinking and reasoning. The series consists of a Textbook, Workbook and a Teacher’s Guide. The Textbook and Workbook present core science topics in an activity-based environment to develop an inquiring mind in students. The Teacher’s Guide provides support for teachers to help students acquire the key knowledge and skills they need in order to understand and develop their creative and critical thinking skills in science. Textbook Each chapter begins with a highly colourful image to attract the students to the exciting content that follows. The purpose of the opening page is to encourage as much discussion as possible with the probing questions. It provides a good opportunity for teachers to assess students’ prior knowledge. It also tells the students what they are aiming to study. The key information in the text sets out the key facts and ideas that students need to know and understand. The content is presented with attractive visuals, pictures and diagrams to attract the attention of students and is linked directly to the learning objectives of the chapter. The key facts and ideas are reinforced by activities such as “Experiment”, “Activity”, “Project” and “Think About It”. These activities help students understand key ideas better and develop their scientific skills. They are required to work in pairs or small groups to present and share their findings with the whole class. Workbook The exercises provided in the Workbook are closely linked to the respective lessons in the Textbook to facilitate the teaching and learning process. The exercises are presented in a variety of formats and aimed at helping students learn more facts and understand the ideas and concepts better for each lesson. Two sets of assessment papers are included in the workbook to assess how well the students have understood the lessons learned. Teacher’s Guide The Teacher’s Guide is the main resource for teachers to start a chapter. It contains the scheme of work (lesson plan overview) that highlights the resources in the Textbook, Workbook and Teacher’s Guide for all the lessons in the chapter. The scheme of work also indicates the learning outcomes, suggested teaching approaches and estimated time allocation for each lesson in the chapter. The Teacher’s Guide provides guidelines to teachers on how to begin, develop and conclude the lessons in a chapter under several headings. Introduction Provide clear science information and facts to help teachers understand what they are going to teach in the chapter. Lessons and Learning Objectives Indicate all the lessons in the chapter and explain what students should know or do as a result of a learning experience. Teacher’s Guide Focus-on Science Grade 8 xi © Praxis Publishing Singapore Pte. Ltd. ©Praxis Publishing_Focus On Science

Key Terms Specific words or phrases that students are required to learn in the chapter. For each lesson in the chapter, the headings are: Learning Outcomes Describe the knowledge, skills or attitudes that students are expected to achieve after completing the lesson. Key Understanding Core ideas or concepts that students should gain from the lesson. Induction Engage students with the lesson and initiate whole-class discussion. The questioning technique is applied to elicit discussion and to find out what the students already know. Teaching and Learning Activities Set the lesson presentation mode. The activities include discussions, experiments and projects to enable students to master scientific concepts and skills, as well as develop scientific attitudes. Various approaches are suggested, including inquiry-based learning, contextual learning, experiential learning and collaborative learning. Assessment and Evaluation Gather information or evidence and make judgments about students’ learning and progress. Scoring rubrics are guidelines that teachers use to assess students’ performance in tasks, assignments or projects. They provide a standardised framework for evaluating different aspects of the work. Rubrics also provide feedback to students, highlighting their strengths and areas for improvement based on the defined criteria and scoring. Closure Help students reflect and consolidate their learning by summarising the key points of the lesson. Extension / Follow-up Activities Additional activities are provided to further enhance students’ understanding of the concepts and skills learned, making the learning experience more meaningful. Some of these activities include model making, games and quizzes, and research on current issues. Textbook Answers Detailed explanations or solutions provided for questions or problems in the Textbook, such as answers to the questions in “Experiment”, “Activity”, “Think About It”, “Recall” and “Put on Your Thinking Cap”. The answers to the “Exercises” in the Workbook are provided separately as a separate component. The URLs in the Teacher’s Guide were reviewed and deemed suitable at the time of publication. Teacher’s Guide Focus-on Science Grade 8 xii © Praxis Publishing Singapore Pte. Ltd. ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 xiii © Praxis Publishing Singapore Pte. Ltd. Skill Lacks proficiency (1) Partially proficient (2) Proficient (3) Advanced (4) Self-motivation Consistently fails to meet established deadlines. Takes initiative to complete assignments and improve or correct behaviours. Occasionally completes and turns in assignments before the scheduled deadline. Never misses a deadline and often completes assignments well ahead of deadlines. Communication Unable to speak or write clearly and to correct behaviours despite intervention by instructors, does not listen actively. Needs work to speak or write clearly; sometimes able to identify alternative communication strategies. Speaks clearly, writes legibly, listens actively and adjusts communication strategies to various situations. Comfortably utilises a variety of communication styles, writes legibly, speaks clearly and listens actively. Teamwork Manipulates the team or acts with disregard to the team, disrespectful to team members, resistant to change or refuses to cooperate in attempts to work out solutions. Sometimes acts for personal interest at the expense of the team, acts independent of the team or appears unsupportive, and is occasionally unwilling to work out a solution. Places the success of the team above self-interest, does not undermine the team, helps and supports other team members, and shows respect to all team members. Places success of the team above self-interest, takes a leadership role and uses good management skills while leading, and involves all team members in the decision-making process. Neatness The work appears sloppy and disorganised. It is hard to know what information goes together. The work is organised but may be hard to read at times. The work is neat and organised. It is easy to read. The work is neat, clear and organised. It is easy to read. Completion Most of the work is incomplete even when additional time or suggestions are given. Some work is incomplete and needs additional suggestions. Some work is incomplete and needs additional time. All work is complete. Responsibility Always relies on others to complete assignments. Rarely does the work and needs constant reminders to stay on the task. Rarely does the work and needs constant reminders to stay on the task. Always does assigned work without being reminded. Scoring Rubric for Affective Domain ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 xiv © Praxis Publishing Singapore Pte. Ltd. Skill Lacks proficiency (1) Partially proficient (2) Proficient (3) Advanced (4) State problem/ question Needs assistance to state the problem or identify the information. Sometimes states the problem or identifies the information correctly. Occasionally states the problem or identifies the information correctly. Works alone and correctly states the problem and identifies the information and the steps needed to arrive at a solution. Conclusion/ Synthesis thinking ability Conclusions drawn are lacking, incomplete or confusing and needs help to write a conclusion or answer questions. Sometimes asks for guidance to write or complete a conclusion. Occasionally answers questions and writes a conclusion in complete sentences. Always writes a response to whether the hypothesis is right or wrong and answers in complete sentences. Using scientific reasoning for explanation No evidence of scientific reasoning is used. Some pieces of evidence of scientific reasoning are used. Effective scientific reasoning is used. Employs refined and complex reasoning and demonstrates understanding of cause and effect. Using scientific concepts and related content Always relies on others in using scientific concepts. Provides minimal reference to relevant scientific concepts, principles or big ideas. Provides evidence of understanding of relevant scientific concepts, principles or big ideas. Provides evidence in depth and sophisticated understanding of relevant scientific concepts, principles or big ideas. Scoring Rubric for Scientific Thinking ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 xv © Praxis Publishing Singapore Pte. Ltd. Skill Lacks proficiency (1) Partially proficient (2) Proficient (3) Advanced (4) Creativity The project has little creative and unique aspects. The project has some creative and unique aspects. The project has adequate creative and unique aspects. The project has plenty of creative and unique aspects. Communication and collaboration The information is not organised. Data is presented inaccurately. There is no drawing plan. Some information is clear and organised. There is a drawing plan without any labels. Most information is clear and organised. There is a clearly labelled drawing plan. All information and data are clear and organised. They are presented accurately. There is a clearly labelled drawing plan. Technology operations No technological resources are used in the project or are not used correctly. Few technological resources are used in the project or are not used correctly. Technological resources are used in the project correctly. Multiple technological resources are used appropriately. Teamwork Students demonstrate no cooperation, courtesy, enthusiasm, confidence or accuracy. Students demonstrate little cooperation, courtesy, enthusiasm, confidence or accuracy. Most students demonstrate some cooperation, courtesy, enthusiasm, confidence and accuracy. All students demonstrate high levels of cooperation, courtesy, enthusiasm, confidence and accuracy. Presentation Presentation lacks details needed to understand the team’s solution. Presentation provides an adequate explanation of how the solution is developed and how it works. Presentation or visual aids provide a clear, effective, and creative explanation of how the solution is developed and how it works. Presentation and visual aids provide a very clear, effective and creative explanation of how the solution is developed and how it works. Scoring Rubric for STEM Activities / Projects ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 xvi © Praxis Publishing Singapore Pte. Ltd. Chapter 1: Introduction to Cells Lesson Learning outcomes Resources Time allocation Textbook Workbook Teacher’s Guide Approach 1.1 Cells and Microscopes • Understand what cells are and that organisms are made up of cells • Know the history of microscopes which includes the discoverers of cells • Know the basic features of a light microscope and an electron microscope and can differentiate them • Know the different parts of a light microscope • Know how to use and handle a light microscope including the preparation of specimen slides Exercises 1–9 (pp. 1–4) Extra info: Robert Hooke (p. 1) Anton van Leeuwenhoek (p. 2) Induction (p. 2) Teaching and learning activities (pp. 2–3) Assessment and evaluation (p. 3) Closure (p. 3) Extension / followup activities: Presentation of analogy for a cell (p. 4) Reflective assignment on light microscope (p. 4) Students’ participation in class discussions by − giving facts about what the human body is made of − giving everyday meaning and the scientific meaning of cells: Constructivism Discussion about the discoverers of cells and scientists related to the discoveries about cells. Ancient microscopes used by them are also discussed: Collaborative Discussion about the differences between light microscope and electron microscope: Collaborative Student participation in followup activities by − presenting analogies of a cell − carrying out reflective assignment on light microscope: Constructivism/Contextual 8 periods (Weeks 1 & 2) Scheme of Work [Note: The suggested teaching time can be altered according to the needs of the lessons.] ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 xvii © Praxis Publishing Singapore Pte. Ltd. Chapter 1: Introduction to Cells Lesson Learning outcomes Resources Time allocation Textbook Workbook Teacher’s Guide Approach 1.2 Animal and Plant Cells • Know how to prepare specimen slides which include slides of animal and plant cells • Observe animal and plant cells under a light microscope • Compare and contrast animal and plant cells Activity 1: Observing human cheek cells (p. 5) Activity 2: Observing onion cells (p. 6) Think About It (p. 7) Exercises 1−7 (pp. 5−7) Induction (p. 4) Teaching and learning activities (pp. 5−6) Assessment and evaluation (p. 6) Closure (p. 6) Extension / follow- up activities: Distinguishing between animal and plant cells on slides (p. 6) Building model of animal and plant cells (p. 6) Quiz on animal and plant cells (p. 7) Textbook answers (p. 7) Discussion about how a typical cell looks like and its parts by showing real photos or diagrams of animal and plant cells: Contextual Activity: 1 Inquiry: Activity 2: Inquiry: Student participation by − drawing animal and plant cells without referring to the textbook with the parts labelled. − filling up a comparison table between animal and plant cells: Constructivism Student participation in follow- up activities by − distinguishing between animal and plant cells on slides shown to them − building models of animal and plant cells based on their creativity preferably using recycled material − taking part in a quiz about animal and plant cells: Collaborative 12 periods (Weeks 2 & 3) ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 xviii © Praxis Publishing Singapore Pte. Ltd. Chapter 1: Introduction to Cells Lesson Learning outcomes Resources Time allocation Textbook Workbook Teacher’s Guide Approach 1.3 Unicellular and Multicellular Organisms, and Cell Specialisation • Know what unicellular and multicellular organisms are • Give examples of unicellular and multicellular organisms and know the similarities and differences between them • Give examples of specialised cells of animals and plants and their functions Think About It (p. 9) Exercises 1−3 (pp. 8−9) Extra info: Unicellular and multicellular organisms (p. 8) Induction (p. 8) Teaching and learning activities (p. 8) Assessment and evaluation (p. 8) Closure (p. 9) Textbook answers (p. 9) Student participation by − giving examples of unicellular and multicellular organisms and their similarities and differences − giving examples of specialised cells in animal and plant cells: Collaborative 4 periods (Weeks 3 & 4) End-of-chapter materials Recall (p.12) Put on Your Thinking Cap (p. 13) Project: The Ethical Issues of Stem Cell Research (p.14) Objective Questions (pp. 10−11) Concept Map (p. 12) HOTS Daily Application (p. 13) Online Quick Quiz (p. 13) Textbook answers: (p. 9) Project: The Ethical Issues of Stem Cell Research (pp.10−11) Put on Your Thinking Cap & HOTS Daily Application: HOTS The Ethical Issues of Stem Cell Research: 21st century skills 8 periods (Weeks 4 & 5) Midterm assessment Assessment 1 (pp. 81−88) ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 xix © Praxis Publishing Singapore Pte. Ltd. Chapter 2: Structures and Functions of the Human Body Systems Lesson Learning outcomes Resources Time allocation Textbook Workbook Teacher’s Guide Approach 2.1 Food and Digestive System • Understand the nutrients obtained from food • Describe the importance of carbohydrates, proteins, fats, vitamins and minerals in our diet • Know the importance of water in life processes • Know what a balanced diet is and its constituents • Calculate energy value of food • Know the factors affecting the daily energy requirement of individuals • Understand how to differentiate healthy meals and unhealthy meals • Know the classes of food additives, their function and the side effects caused by excessive intake • Recognise each part of the human digestive system and know its role in digestion Think About It (p. 16) Think About It (p. 17) Think About It (p. 18) Think About It (p. 19) Think About It (p. 29) Think About It (p. 32) Think About It (p. 34) Activity 1: Understand vitamins (p. 24) Activity 2: Understand food labels (p. 27) Activity 3: Understand food additives (p. 32) Exercises 1−16 (pp. 1−21) Extra info: Reading food label (p. 15) MyPlate (p. 16) Human digestive system (p. 19) Induction (p. 13) Teaching and learning activities (pp. 13−16) Assessment and evaluation (p. 16) Closure (pp. 17−19) Extension / follow- up activities: Testing food (pp. 19−20) Investigating the amount of sugar and salt in foods (p. 20) Conducting an experiment to estimate the energy value of a food sample (pp. 20−21) Making a model of MyPlate (p. 21) Textbook answers (pp. 21−22) Students’ participation in class discussions by − justifying the need to eat or the importance of the food they consumed. − identifying the nutrients in a variety of food − giving examples of fats from plant and animal sources − giving their understanding of cholesterol − giving other examples of sources of minerals − giving their opinion on water consumption − giving their understanding of what a balanced diet is − comparing daily energy requirements of individuals − justifying healthy and unhealthy meals − categorising healthy and unhealthy food bought from grocery store − visualising what happens to the food they eat − justifying the importance of taking care of teeth: Collaborative learning 14 periods (Weeks 5–7) Scheme of Work [Note: The suggested teaching time can be altered according to the needs of the lessons.] ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 xx © Praxis Publishing Singapore Pte. Ltd. Chapter 2: Structures and Functions of the Human Body Systems Lesson Learning outcomes Resources Time allocation Textbook Workbook Teacher’s Guide Approach • Describe the processes of food digestion and know the main organs involved • Describe the processes of absorption of digested food and defaecation Activity 4: Analyse the action of enzyme (p. 35) Discussion about different types of nutrients in food: Contextual Discussion about the categories of vitamins and the variety of minerals: Contextual Discussion about balanced diet: Contextual Discussion about factors that affect the daily energy requirement of an individual: Contextual Discussion about food digestion: Contextual Student participation in follow- up activities by − testing food − investigating the amount of sugar and salt in foods − conducting an experiment to estimate the energy value of a food sample − making a model of MyPlate: Contextual/ Constructivism Activity 1 & 2: Inquiry: Activity 3 & 4: Contextual ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 xxi © Praxis Publishing Singapore Pte. Ltd. Chapter 2: Structures and Functions of the Human Body Systems Lesson Learning outcomes Resources Time allocation Textbook Workbook Teacher’s Guide Approach 2.2 Circulatory System • Identify the structures and organs of the circulatory system • Describe what the circulatory system does • Recognise the components of blood and their functions • Compare the types of blood vessels • Describe the structure of the heart and how it works • Know the diseases related to the heart and blood vessels Think About It (p. 40) Think About It (p. 44) Activity 5: Determining the heart rate per minute at rest and after exercising (p. 43) Exercises 1−11 (pp. 21–26) Extra info: Human heart (p. 23) Induction (p. 22) Teaching and learning activities (pp. 22–24) Assessment and evaluation (p. 25) Closure (pp. 25–26) Extension / follow- up activities: Making a simple stethoscope (p. 26) Textbook answers (p. 27) Discussion about materials transported in the body and the circulatory system: Contextual Discussion about the differences between arteries, veins and capillaries: Contextual Activity 5: Experiential learning Student participation by − showing the location of their heart and stating its role − naming several diseases related to the heart and blood vessels − coming up with some basic rules to keep their heart healthy: Collaborative Student participation in follow- up activities by − making a simple stethoscope: Experiential learning 12 periods (Weeks 7−9) ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 xxii © Praxis Publishing Singapore Pte. Ltd. Chapter 2: Structures and Functions of the Human Body Systems Lesson Learning outcomes Resources Time allocation Textbook Workbook Teacher’s Guide Approach 2.3 Respiratory System • Describe the structures and organs of the respiratory system • Explain how gas exchange takes place in the alveoli of the lungs • Describe the movement of the rib cage and diaphragm during inhalation and exhalation • Know the diseases related to the respiratory system Activity 6: Counting our breaths (p. 46) Activity 7: Understand the breathing mechanism (p. 48) Exercises 1−10 (pp. 26−31) Extra info: Effects of smoking (p. 30) Induction (p. 27) Teaching and learning activities (pp. 27−28) Assessment and evaluation (p. 28) Closure (pp. 29) Extension / follow- up activities: Testing the gas we breathe out (p. 29) Textbook answers (p. 30) Student participation by − answering questions related to breathing and the gases involved − giving their opinion on the breathing rate for different situations − coming up with some basic rules to protect their respiratory system: Contextual Discussion about inhalation and exhalation: Contextual Discussion about breathing mechanism: Contextual Discussion about the diseases of the respiratory system: Contextual Discussion about the importance of taking good care of the respiratory system: Contextual Student participation in follow- up activities by − testing the gas they breathe out: Experiential learning 10 periods (Weeks 9 & 10) ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 xxiii © Praxis Publishing Singapore Pte. Ltd. Chapter 2: Structures and Functions of the Human Body Systems Lesson Learning outcomes Resources Time allocation Textbook Workbook Teacher’s Guide Approach 2.4 Excretory System • Explain the excretion process • Identify the organs of the excretory system and their excretory products • Know the health effects of smoking, alcohol consumption and drug addiction Think About It (p. 51) Exercises 1−3 (p. 32) Induction (p. 30) Teaching and learning activities (pp. 30−31) Assessment and evaluation (p. 31) Closure (pp. 32−33) Textbook answers (p.33) Student participation by − giving their opinion on sweating and passing urine − detecting the presence of water in exhaled air − coming up with a poster on the harmful substances in cigarette smoke and their effects to the body − giving their understanding of taking medicine: Contextual Discussion about the importance of getting rid of waste products: Contextual Discussion about the difference between medicine and drugs: Contextual Discussion about the short- term and long-term effects of consuming alcohol: Contextual 6 periods (Weeks 10 & 11) ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 xxiv © Praxis Publishing Singapore Pte. Ltd. Chapter 2: Structures and Functions of the Human Body Systems Lesson Learning outcomes Resources Time allocation Textbook Workbook Teacher’s Guide Approach End-of-chapter materials Recall (p.53) Put on Your Thinking Cap (p. 54) Project: Risk Factors that Impact Heart Health (p. 55) Objective Questions (pp. 33–34) Concept Map (p. 35) HOTS Daily Application (p. 36) Online Quick Quiz (p. 36) Textbook answers (p. 33) Project Guide: Risk Factors that Impact Heart Health (p. 34) Put on Your Thinking Cap & HOTS Daily Application: HOTS Risk Factors that Impact Heart Health: 21st century skills 8 periods (Weeks 11 & 12) Midterm assessment Assessment 1 (pp. 81−88) ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 1 © Praxis Publishing Singapore Pte. Ltd. Introduction Cells are the basic unit of organisms. Humans, animals and plants are made up of cells. All organisms are made up of either one cell only, known as unicellular organisms or of many cells, known as multicellular organisms. The amazing world of cells is discovered through the microscope. Different types of cells of various shapes and sizes can be observed through the microscope. Students will learn to differentiate between plant and animal cells, as well as their different parts and functions. Students are introduced to specialised cells in which their structures are related to their functions. Lessons and Learning Objectives 1.1 Cells and Microscopes • Understand what cells are • Know the history of microscopes • Differentiate between a light microscope and an electron microscope • Proper handling of a light microscope including the preparation of specimen slides 1.2 Animal and Plant Cells • Compare and contrast between animal and plant cells 1.3 Unicellular and Multicellular Organisms, and Cell Specialisation • Compare and contrast between unicellular and multicellular organisms • Give examples of specialised cells and their functions Key Terms 1.1 cells, basic unit of organism, microscope, light microscope, electron microscope 1.2 animal cell, plant cell, mitochondrion, cytoplasm, cell membrane, nucleus, cell wall, chloroplast, vacuole 1.3 unicellular organism, multicellular organism, cell specialisation, specialised cell Introduction to Cells CHAPTER 1 ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 2 © Praxis Publishing Singapore Pte. Ltd. Lesson 1.1 Cells and Microscopes Learning Outcomes • Understand what cells are and that organisms are made up of cells • Know the history of microscopes which includes the discoverers of cells • Know the basic features of a light microscope and an electron microscope, and can differentiate them • Know the different parts of a light microscope • Know how to use and handle a light microscope Key Understanding Cells are the building blocks of an organism. They make humans and animals such as cats, frogs and fish. They also make plants such as grass and coconut trees. In the human body, there are about 37.2 trillion cells in various shapes and sizes. Apart from those cells in the human body, there are other cells such as bacteria and fungi especially in the bowels. Cells are very tiny, thus only visible under a microscope. The scientists who are involved in the discovery of cells used a microscope to study them. In school laboratories, light microscopes are used to study cells and other tiny specimens, thus the proper handling of the microscope must be emphasised. Induction 1 Start off with a discussion by asking students what their bodies are made of. Tell them that there are about 37.2 trillion cells of various shapes and sizes in our body. Let them know that there are also other cells in the body such as bacteria and fungi especially in the bowels. 2 Ask the students to come up with the everyday meaning and the scientific meaning of cells. For example, Legos or building blocks which come in various shapes and sizes are used to construct an object. In comparison, cells which also come in various shapes and sizes make up all living things. Cells are the building blocks of life. 3 Encourage students to ask questions and participate in discussions on the brief history of microscopes. Introduce Robert Hooke and Anton van Leeuwenhoek, who are the discoverers of cells. Teaching and Learning Activities Textbook p. 2 1 Talk about cells. Request students to come up with analogies to describe a cell and its main parts which include the nucleus, cytoplasm, and cell membrane. For example, a cell is like a school in which the nucleus is like the main office in a school which controls and runs the operation of the entire school. 2 Point out to the students that cells are too tiny to be seen by the naked eye, therefore a special device, the microscope, is required to see them. Talk about the discoverers of cells, Robert Hooke and Anton van Leeuwenhoek, and the microscopes they used to study the cells. Robert Hooke was the first person to discover and name cells by observing them under a microscope in 1665. The microscope which he created himself has a magnification up to 50 times, thus he could observe objects smaller than anyone had ever seen before. However, what he observed were actually dead cell walls of plant cells known as cork. The cork which looked like it was made of tiny compartments that resemble the cells in a monastery, were eventually named ‘cells’ by Robert Hooke. Van Leeuwenhoek is mainly credited with the discovery of microbes which he observed under the microscope he himself created. ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 3 © Praxis Publishing Singapore Pte. Ltd. 3 A video about cells can be viewed by scanning the QR code given on p. 2. In this video, several scientists other than Robert Hooke who were involved in the discovery related to cells are shown. They are Robert Brown, Dr Schwann and Dr Schleiden. Robert Brown discovered the cell nucleus whereas Dr Schwann and Dr Schleiden came up with the theory that cells are alive and that they are the basic building blocks of life. A segment of the video also shows the general structure of cells and the specialised cells found in animals and plants. Textbook pp. 3–4 4 Let them know that there are two common types of microscopes: light microscope and electron microscope. A light microscope can either have one eyepiece or two eyepieces. Refer to the diagrams shown on p. 3. 5 Discuss the differences between light microscope and electron microscope. 6 Show students a light microscope. Talk about each part and its function, especially the magnification of all three objective lenses. Explain the steps in the proper handling of a light microscope. 7 For further details, students can scan the QR code on p. 4 to view the video on ‘Using a microscope’. Assessment and Evaluation 1 Assess students’ understanding of cells and microscopes by observing their participation in class discussions, and whether they had shared their thoughts. 2 Assess students’ critical thinking skills, attitudes and values, through observation of their participation during the discussion about the analogies of cells. 3 Have students complete Exercises 1−9 Workbook pp. 1–4 . Students can obtain extra info about Robert Hooke and Anton van Leeuwenhoek via the QR code given. 4 Provide feedback to students on their performance, highlighting areas where they achieved and areas where they need to improve. Closure To summarise the important ideas and concepts taught in the lesson, consider using the key points provided through strategies such as a class discussion, a summary statement, a quiz, a visual organiser or a reflective writing assignment. Allow students to ask any additional questions for clarification or clear up any doubts. Brief History of Microscopes 1 All organisms are made up of cells. Since cells are very tiny, a microscope is used to see how they look like. Under the microscope, the cells look clearer and magnified many more times than they really are. The common microscopes used in school laboratories are the light microscopes. 2 With the help of microscopes, scientists were able to study cells. 3 Robert Hooke was the first person to study cells using a compound microscope with two lenses. Light Microscope and Electron Microscope 4 Light microscope and electron microscope are the most common types of microscopes. 5 Both the microscopes magnify specimen being observed. The light microscope uses light ray whereas the electron microscope uses electron beam to produce the image of a specimen. 6 The light microscope is called a compound microscope because it contains two types of lenses to magnify an object, namely the eyepiece and the objective lens. ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 4 © Praxis Publishing Singapore Pte. Ltd. How to Use a Light Microscope 7 A student must be familiar with the parts of a light microscope and know their functions before using it. 8 There are certain steps that a student must follow when using a light microscope. Extension / Follow-up Activities 1 Presentation of analogy for a cell (a) Group the students into smaller groups. (b) Ask each group to choose an analogy for a cell. For example, the parts of the cell have similar functions to the various services in a city. Ask them to come up with a brief presentation using a poster of a city showing various buildings in it which are the cell parts. 2 Reflective assignment on light microscope Show the students a microscope or a diagram of a microscope on the board. (a) Point out any part of the microscope and call up any student to name them. (b) Ask them to calculate the magnification being used on the microscope. For example, if the magnification of the eyepiece is 10X and the magnification of the objective lens in use is 40X, the total magnification being used is 10 × 40 = 400 based on the following formula. Total magnification = magnification of eyepiece × magnification of objective lens Emphasise to students that the magnification of the objective lens depends on the one being used to magnify the specimen. Lesson 1.2 Animal and Plant Cells Learning Outcomes • Know how to prepare specimen slides which include slides of animal and plant cells • Observe animal and plant cells under a light microscope • Compare and contrast between animal and plant cells Key Understanding All plants and animals are made up of units called cells. Cells come in many shapes and sizes. A typical cell is enclosed by a cell membrane that controls what enters and leaves the cell. The nucleus controls all the activities of the cell. Plant cells differ from animal cells but they both contain a few basic parts which are the nucleus, cell membrane and cytoplasm. Induction 1 Start the discussion on how a typical cell looks like or the basic structure of a cell. 2 Encourage students to ask questions and participate in the discussion on the parts of plant and animal cells. Show some real photos or diagrams of plant and animal cells. Ask students what is the most obvious difference that they can see between both the cells. ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 5 © Praxis Publishing Singapore Pte. Ltd. Teaching and Learning Activities Textbook pp. 5–6 1 Divide the students into groups. Let them carry out Activity 1, followed by Activity 2. Students must be guided in producing a microscope slide of their own. Sometimes, several attempts are required in slide making before the students can come up with a slide that can be properly viewed under the microscope. Let them know that cells are three-dimensional structures even though they look like twodimensional structures under the light microscope. Activity 1: Demonstrate how the students should scrape the inside of their cheeks with the blunt end of a toothpick (alternative: cotton bud), place the scraping on a glass slide ensuring an even covering, and lower a cover slip over it using a mounting pin. Let them know that the methylene blue solution added is used to stain certain part of the cells such as the nuclei of the cells so that they become more visible. Each student is given a chance to observe the cells through the microscope. Ask them to guess the number of cells that they can see on the slide. Point out that each slide contains numerous cells. Have students draw pictures of what they see under the microscope using the diagram on p. 7 as a guide. Safety: Warn students that cover slips can break easily and that the mounting pin is sharp. Point out to them that methylene blue must be handled with care as it can permanently stain skin. Students must also throw used toothpicks in the designated bin after use and make sure they do not touch anyone else’s toothpick. Activity 2: Guide the students in preparing a slide of onion cells. Demonstrate how to peel the inner transparent epidermal layer from the inner scale leaves of an onion, how to place it on a slide and how to lower a cover slip over it using a mounting pin. Let them know that a drop of iodine is added because it binds to starch molecules, turning them blue-black, thus making the structure in the cell easier to view. Have students draw pictures of what they see under the microscope using the diagram on p. 7 as a guide. Ask them questions as given below. (a) Why do you need to put the onion epidermal layer on a drop of water as soon as you remove it from the onion? (This is to ensure that it does not dry out as no visible parts of the cells can be seen if it becomes dry.) (b) Are all the cells you see under the microscope the same type of cell? (Yes, they are all onion cells) (c) If a slide of spinach cells is compared to a slide of onion epidermal cells above, predict the difference that you will notice. Explain. (Chloroplasts, which are the site for photosynthesis can be seen on the slide of spinach cells. There are no chloroplasts in onion epidermal cells because onion bulbs are used for food storage, and they grow underground where they do not receive light.) 2 Ask the students what differences they noticed between the plant and animal cells under the microscope. 3 However, if there are insufficient or no microscopes available, secondary sources such as projected colour slides of plant and animal cells can be used. 4 Point out to the students that, unlike animal cells, plant cells have a fixed shape with large vacuoles. The size of the vacuole increases and decreases depending on the amount of water and sap stored in it. When a plant lacks water, the vacuole decreases in size, causing the cell to cave in on itself and causing the plant to wilt. ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 6 © Praxis Publishing Singapore Pte. Ltd. Textbook p. 7 5 Discuss the main parts of a plant cell and an animal cell. Explain to the students the function of each part. Then, give the students an on-the-spot assignment in which they need to draw and label a plant cell and an animal cell without referring to the textbook. 6 Get the students to answer the question in ‘Think About It’. Textbook p. 8 7 Discuss the similarities and the differences between animal and plant cells. Then, draw a comparison table on the board. Get volunteers to fill in the table. 8 Get the students to read through the ‘Science Facts’ about the largest and smallest human cells. Assessment and Evaluation 1 Assess students’ understanding of the similarities and differences between plant and animal cells by observing their participation in class discussions, whether they provide examples, scenarios, share their thoughts, or work in pairs or small groups. 2 Assess students’ scientific and critical thinking skills, attitudes and values, through observation of their participation during Activities 1 to 2 and review their results, discussions and conclusions. 3 Have students complete Exercises 1−7 Workbook pp. 5–7 . Closure To summarise the important ideas and concepts taught in the lesson, consider using the key points provided through strategies such as a class discussion, a summary statement, a quiz, a visual organiser or a reflective writing assignment. Allow students to ask any additional questions for clarification or clear up any doubts. Comparison Between Animal Cells and Plant Cells 1 The basic parts found in animal and plant cells are the nucleus, cell membrane and cytoplasm. 2 Plant cells have a fixed shape due to their cell wall, which is absent in animal cells. 3 Most plant cells contain chloroplasts which are absent in animal cells. 4 Both animal and plant cells have vacuoles, but plant cells normally have one large vacuole while animal cells have many small vacuoles or none. Extension / Follow-up Activities 1 Distinguishing between animal and plant cells on slides Teacher can show the students projected colour slides of various plant and animal cells. Ask students whether the slide shows animal cells or plant cells and get them to justify their answer. For example, teacher can show them the projected slide of Hydrilla cells and ask them whether the cells are plant or animal cells. (The cells have a cell wall and a fixed shape, therefore they are plant cells.) 2 Building model of animal and plant cells Divide the students into groups of five. Encourage the students to get creative by making a threedimensional model of a plant cell or an animal cell using any materials such as art and craft materials, modeling clay, preferably recycled materials. Get them to label the basic parts of the cell as creative as possible. ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 7 © Praxis Publishing Singapore Pte. Ltd. 3 Quiz on animal and plant cells Teacher can conduct a quiz by forming several teams. Teacher will then distribute cards with twenty true and false statements about animal and plant cells. The team with the highest correct answers in the time frame given is the winner. Examples of statements: • Only animal cells have cell membranes. (True/False) • All plant cells have cytoplasm. (True/False) • Plant and animal cells have a nucleus. (True/False) • Animal cells have a fixed shape. (True/False) • Mitochondria in cells produce energy from digested food. (True/False) Textbook Answers Activity 1 p. 5 Observation: Cell membrane Nucleus Cytoplasm Discussion: 1 The methylene blue solution colours the cheek cells so that their structures can be observed clearly. 2 The shapes of cheek cells are irregular. Conclusion: 1 Animal cells do not have fixed shapes. 2 An animal cell contains a nucleus, cell membrane and cytoplasm. Activity 2 p. 6 Observation: Nucleus Vacuole Cytoplasm Cell wall Discussion: 1 The iodine solution colours the nucleus reddish-brown and the chloroplasts dark blue so that their structures can be observed clearly. 2 The shape of onion cells is regular. Conclusion: 1 Plant cells have fixed shapes. 2 A plant cell contains a nucleus, cell membrane, cell wall, cytoplasm and a large vacuole. Think About It p. 7 Leaves, because they carry out photosynthesis to make food. ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 8 © Praxis Publishing Singapore Pte. Ltd. Lesson 1.3 Unicellular and Multicellular Organisms, and Cell Specialisation Learning Outcomes • Know what unicellular and multicellular organisms are • Give examples of unicellular and multicellular organisms and know the similarities and differences between them • Give examples of specialised cells of animals and plants and their functions Key Understanding Unicellular organisms, which are also known as microscopic organisms, are organisms that are made up of one cell. They are too tiny and thus cannot be seen with the naked eye. Only through the magnification of a microscope, can they be viewed. Multicellular organisms are organisms that are made up of more than one cell of different types. Each type of cell has a different structure and carries out a specific function. However, both unicellular organisms and multicellular organisms perform all the processes of life, such as respiration, response, digestion, excretion, reproduction and growth. Induction 1 Use examples given on p. 9 of the textbook to start the discussion of unicellular organisms and multicellular organisms. 2 Encourage students to ask questions and participate in discussion about the similarities and differences between the unicellular and multicellular organisms. Teaching and Learning Activities Textbook p. 9 1 Hold a discussion and get students to give examples of unicellular and multicellular organisms that they know. 2 Emphasise that both unicellular and multicellular organisms carry out all the processes of life. 3 Get students to answer the questions in ‘Think About It’. Then, go through the ‘Science Facts’ about viruses with them. Textbook pp. 10–11 4 Emphasise that not all cells that make up our body are the same. 5 Introduce cell specialisation by explaining its definition and its importance. 6 Talk about the specialised cells found in animal and plant cells and their functions. Request students to come up with other examples of specialised cells in animal and plant cells. Assessment and Evaluation 1 Observe how students participate in class discussions. 2 Have students complete Exercises 1−3 Workbook pp. 8−9 . Students can get extra info about unicellular and multicellular organisms via the QR code given. 3 Provide feedback to students on their performance, highlighting areas they achieved and areas they need to improve on. ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 9 © Praxis Publishing Singapore Pte. Ltd. Closure • To summarise the important ideas and concepts taught in the lesson, consider using the key points provided through strategies such as a class discussion, a summary statement, a quiz, a visual organiser or a reflective writing assignment. Allow students to ask any additional questions for clarification or clear up any doubts. Unicellular and Multicellular Organisms 1 Unicellular organisms are organisms that are made up of one cell only and are invisible to the naked eye. 2 Amoeba, Euglena, Paramecium, Chlamydomonas and bacteria such as Escherichia coli are examples of unicellular organisms. 3 Multicellular organisms are organisms that are made up of many cells and visible to the naked eye. They have a complex body organisation and their size increases as the number of cells in them increases. 4 Humans, plants, animals and some fungi and algae are examples of multicellular organisms. 5 Some of the differences between unicellular and multicellular organisms are: (a) Unicellular organisms have only one cell which performs all the necessary processes of life while multicellular organisms have numerous different types of cells which perform different functions. (b) The entire body of a unicellular organism is exposed to the environment but for a multicellular organism, only the outer cells are exposed to the environment. Cell Specialisation 6 Specialised cells are cells of different shapes and structures doing different jobs. 7 Nerve cells, bone cells, red blood cells, muscle cells, sperms and epithelial cells are examples of specialised animal cells. 8 Guard cells, root hair cells, xylem cells and phloem cells are examples of specialised plant cells. • Ask students to reflect on what they have learned in this chapter by completing the sections ‘Recall’ Textbook p. 12 and ‘Concept Map’ Workbook p. 12 . • Let students complete the ‘Objective Questions’ Workbook pp. 10–11 and ‘Online Quick Quiz’ Workbook p. 13 to check their mastery of this chapter. • To reinforce students’ critical thinking skills, have them answer the questions in ‘Put on Your Thinking Cap’ Textbook p. 13 and ‘HOTS Daily Application’ Workbook p. 13 that require them to analyse, evaluate or create based on the knowledge they have acquired. • Give students a preview on what will be covered in the upcoming chapter to help them get ready. • Before proceeding to the next chapter, evaluate students’ performance in the midterm assessment Workbook pp. 81 – 88 . Textbook Answers Think About It p.9 Both unicellular and multicellular organisms carry out all the processes of life: they grow, respond to stimuli, reproduce, pass on genetic material to offspring, and they obtain and use energy. ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 10 © Praxis Publishing Singapore Pte. Ltd. Recall p.12 1 cells 2 cytoplasm 3 energy 4 Robert Hooke 5 Anton van Leeuwenhoek 6 magnify 7 compound 8 diaphragm 9 blue 10 fixed 11 one 12 many 13 multicellular 14 unicellular 15 specialised 16 Muscle 17 photosynthesis 18 animals 19 palisade Put on your Thinking Cap p. 13 1 Cells are the foundation of all living organisms. They form tissues by repeating themselves. Cells, in general, are the repeated units or building blocks of life. 2 All animals are made up of cells which are roughly of the same size. However, the number of cells increases as the body of the animal increases in size. 3 The lack of nuclei allows them to carry more haemoglobin, and thus a greater amount of oxygen can be transported. Project: The Ethical Issues of Stem Cell Research Textbook p. 14 1 Introduction (a) Introduce the concept of stem cell research. (b) Explain to students that they will carry out their research in groups of five. (c) Give a brief overview of the steps involved in the research (gathering information on the Internet and books, analysing information collected, and presenting the finding creatively). 2 Planning and execution (a) Instruct students to elect a leader in their group who can delegate sub-tasks to the group members before planning what information is required and where to search for the information. (b) Provide guidance and support as needed during the planning process. (c) Encourage students to follow their plan carefully. (d) Remind students to gather their information from reliable sources to obtain accurate information. ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 11 © Praxis Publishing Singapore Pte. Ltd. 3 Solution and presentation (a) Instruct students to gather information based on the aspects stated in their textbook but they are encouraged to add more aspects. (b) Allow students to share their findings with the class through a presentation as creatively as possible. They can discuss the similarities and differences in their findings with their peers. 4 Assessment Assess students based on their plan, execution and presentation with the following criteria. (a) The clarity and completeness of the plan (b) The accuracy and completeness of the information gathered (c) The quality of the analysis and conclusions drawn (d) The effectiveness of the presentation and results. ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 12 © Praxis Publishing Singapore Pte. Ltd. Introduction The human body is made up of several systems such as the digestive, circulatory, respiratory and excretory systems. Each system is a group of organs working together in coordination to carry out life functions so that a healthy body is maintained. Lessons and Learning Objectives 2.1 Food and Digestive System • Understand nutrients and balanced diet • List the classes of food additives, their usage and the side effects that arise from their intake • Identify the structures of the human digestive system • Describe the processes of food digestion, absorption of digested food and defaecation 2.2 Circulatory System • Identify the structures and organs of the circulatory system and describe their functions • Know the health issues related to the circulatory system 2.3 Respiratory System • Identify the structures and organs of the respiratory system • Explain breathing mechanisms 2.4 Excretory System • Identify the structures and organs of the excretory system and explain the excretion process • Health effects of smoking, alcohol consumption and drug addiction Key Terms 2.1 nutrients, carbohydrate, fat, protein, mineral, vitamin, water, simple carbohydrate, complex carbohydrate, monosaccharides, disaccharides, polysaccharides, dietary fibre, amino acid, nonessential amino acids, essential amino acids, glycerol, fatty acids, saturated fat, unsaturated fat, trans fat, cholesterol, low-density lipoproteins (LDL), high-density lipoproteins (HDL), water-soluble vitamin, fat-soluble vitamin, balanced diet, nutrition facts label, calories, natural food additives, synthetic food additives, preservatives, colourings, sweeteners, flavourings, essence, antioxidants, digestive system, digestive tract, physical digestion, chemical digestion, mouth, oesophagus, stomach, small intestine, large intestine, anus, liver, gallbladder, pancreas, peristalsis, villi, defaecation 2.2 circulatory system, heart, blood vessels, blood, plasma, red blood cells, white blood cells, platelets, arteries, veins, capillaries, heart, coronary arteries, auricle, ventricle, oxygenated blood, deoxygenated blood, systemic circulation, pulmonary circulation, atherosclerosis, hypertension, heart attack, stroke 2.3 respiratory system, breathing, inhalation, exhalation, nasal cavity, trachea, windpipe, bronchus, thoracic cavity, ribcage, intercostal muscle, diaphragm, bronchiole, alveolus, asthma, bronchitis, emphysema 2.4 excretory system, excretion, skin, lungs, kidneys, liver, smoking, nicotine, tar, carcinogens, carbon monoxide gas, alcohol consumption, drug addiction Structures and Functions of the Human Body Systems CHAPTER 2 ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 13 © Praxis Publishing Singapore Pte. Ltd. Lesson 2.1 Food and Digestive System Learning Outcomes • Understand the nutrients obtained from food • Describe the importance of carbohydrates, proteins, fats, vitamins and minerals in our diet • Know the importance of water in life processes • Know what a balanced diet is and its constituents • Calculate the energy value of food • Know the factors affecting the daily energy requirement of individuals • Understand how to differentiate healthy meals and unhealthy meals • Know the classes of food additives, their function and the side effects caused by excessive intake • Recognise each part of the human digestive system and know its role in digestion • Describe the processes of food digestion and know the main organs involved • Describe the processes of absorption of digested food and defaecation Key Understanding Food is the main source of energy and raw materials for the growth, repair and reproduction of humans. Therefore, eating the right food in the right amount or a balanced diet is important for good health. A balanced diet consists of carbohydrates, proteins, fats, vitamins and minerals. Water is equally essential for a healthy body. The energy we obtain from food is very important for the growth and development of the body. When we eat too little, there will be insufficient energy to carry out our daily tasks. However, when we eat too much, we might probably be at risk of diseases such as cardiovascular diseases. The food we consume needs to be broken down in the digestive system so that the small and soluble molecules produced can be absorbed into the blood and transported to the cells of the body. The digestive tract in which food digestion takes place is long and muscular, extending from the mouth to the anus. It consists of the mouth, oesophagus, stomach, small intestine, large intestine and anus. Digestive juices in the digestive tract which contain enzymes aid in the breakdown of the food. The product of digestion is then absorbed into the blood in the small intestine whereas undigested food is passed out of the body as faeces from the anus. Induction 1 Start the discussion by asking the students what they had for breakfast or lunch that day and why they need to eat or the importance of the food they consumed. 2 Encourage students to ask questions and participate in discussion to help them develop skills in critical thinking and examine what they think about the variety of food they consume and their role. Teaching and Learning Activities Textbook p. 16 1 Discuss about the different types of nutrients in food, which are carbohydrates, proteins, fats, vitamins and minerals. 2 Let students analyse the variety of food shown on p. 16 and talk about the nutrients that can be obtained from each of them. ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 14 © Praxis Publishing Singapore Pte. Ltd. 3 Get students to answer the question in ‘Think About It’. Textbook pp. 17–21 4 Tell the students that there are two types of carbohydrates and review the differences between them. 5 Emphasise the importance of including dietary fibre in the diet. 6 Get students to answer the questions in ‘Think About It’ on pp. 17 and 18. 7 Ask students why protein is important to the body. Talk about the types of amino acids from protein that our body needs: non-essential amino acids that are synthesised by the body and essential amino acids that are obtained from food. 8 Get students to answer the questions in ‘Think About It’ on p. 19. Then, go through the ‘Science Facts’ with them about Kwashiorkor, a disorder caused by severe deficiency of protein and Marasmus, a disorder caused by severe deficiency of protein and calories. 9 Ask students about their understanding of fat and its roles in the body. Get them to give examples of fat from plant and animal sources. 10 Point out to the students that although excess fat can increase the risk to cardiovascular diseases, our body still needs a small amount of fat which is an essential part of a balanced diet. Tell the students that any unused fat, carbohydrates and proteins are converted into body fat. 11 Introduce the terms saturated fat, unsaturated fat and trans fat by referring to the examples given in the diagram on p. 21. 12 Ask the students about their understanding of cholesterol. Discuss about the good cholesterol (highdensity lipoproteins) and bad cholesterol (low-density lipoproteins). Textbook pp. 22–24 13 Discuss both the categories of vitamins: fat-soluble and water-soluble vitamins. 14 Engage students in Activity 1 to further reinforce their understanding of fat-soluble and water-soluble vitamins which include their sources, importance and effects of deficiencies. 15 Discuss the variety of minerals based on the table given on p. 24. Request students to come up with other examples of the sources of minerals that they know. 16 Tell the students that the quantities of vitamins and minerals are so small that special equipment is required to test the presence of vitamins and minerals in food samples. Textbook p. 25 17 Get students’ opinion on why they need to drink water and the amount of water they need to consume daily. Discuss the roles water play in life processes. Textbook pp. 26–29 18 Hold a discussion and get students to give their understanding of what a balanced diet is. Ask them to recall what they have taken for lunch the previous day and determine whether what they took is considered a balanced diet. Explain to them that MyPlate is a simple meal plan. Based on MyPlate, half of the plate should be filled with fruits and vegetables. Then, slightly more than a quarter of the plate should be filled with whole grains and the remainder with protein. A small serving of dairy product should also be included. ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 15 © Praxis Publishing Singapore Pte. Ltd. 19 Stress to them that if they overeat, for example, a diet high in sugar, salt or fat, they may end up with health problems such as diabetes, hypertension and heart diseases. On the other hand, if they eat less than what is required, they will suffer from malnutrition which leads to conditions such as retarded growth and weakening of the immune system. 20 By referring to the food label of the packaged food product shown on p. 26, explain to the students how to get useful information such as the types of nutrients found in the product, the serving size, and the calories per serving of the food product. 21 Divide the students into groups. Let them carry out Activity 2 to further reinforce their understanding of the information stated on food labels and how to choose healthier products wisely. 22 Everyone needs energy to do work, keep warm, move from one place to another, build new tissues and repair damaged tissues. Tell the students that they get their energy from food which can be measured in kilojoules per gram (kJ g−1) or kilocalories per gram (kcal g−1). The quantity of energy in every gram of carbohydrate and protein is 17 kJ g−1 (4 kcal g−1) respectively whereas the quantity of energy in every gram of fat is 37 kJ g−1 (9 kcal g−1). Get the students to calculate the amount of energy in food samples, for example, a chicken bun which contains 16 g of carbohydrate, 3 g of fat and 7 g of protein. Stress to the students that sometimes food that contains lesser quantity of fat might still be high in calories probably because the calories were contributed by high quantity of carbohydrate or sugar. 23 Discuss the factors that affect the daily energy requirement of an individual. Ask them to compare who needs more energy, for example, a person who works as a clerk or a person who works as a car mechanic; a child or a man; a person who is healthy or a person who is down with fever; a person who goes to the gym daily or a person who rarely exercises etc. Textbook p. 29 24 Talk about healthy and unhealthy meals / food. Discuss the harmful effects of eating the wrong types of food, and the diseases associated with this. Get the students to answer the question in ‘Think About It’ to enhance their understanding of healthy and unhealthy meals. 25 Draw a table on the board. Get the students to contribute the list of healthy food and unhealthy food that can be bought from a grocery store. Some of the healthy foods are fruits, vegetables, brown rice, lean meat, fish, egg, milk and nuts. Some of the unhealthy foods are fizzy drinks, sweets, frankfurters, nuggets and potato chips. Ask them why these foods are considered healthy or unhealthy. Students may use the internet to get more examples of foods to be added in the correct column. 26 Ask each student to write down three of their favourite food. Let them identify the nutrients each food contains, which are carbohydrates, proteins, fat, vitamins and minerals. Ask them whether the food they like is healthy or unhealthy based on the nutritional value of each food. Textbook pp. 30–32 27 Introduce the term ‘food additive’. Tell the students that there are natural and synthetic food additives. Talking about natural food additives, ask them if they have seen their mother or anyone else adding something into the food they are preparing to make it taste better or to enhance the flavour. For example, pandan leaves are added in steamed rice to turn it into fragrance rice, koyabu wrapped in pandan leaves gives out a pleasant aroma and pandan extract used in klepon and kue ape gives a beautiful green colour to the desserts/kueh. Get the students to come up with other examples especially local food in which natural food additives were added into the food. ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 16 © Praxis Publishing Singapore Pte. Ltd. 28 Explain to the students about the various classifications of food additives, purpose of using them and their examples by referring to the table given on p. 31. Get the students to answer the question in ‘Think About It’ on p. 32. Talk about the detrimental effects of excessive consumption of food additives found especially in processed food. Get the students to give examples of processed food and the additives added into them. 29 Engage students in Activity 3 so that they can identify all the food additives used in a product and the purpose of using the additives. Get them to also explore further in the Internet about the side effects of the food additives used. Textbook pp. 33–38 30 Start a discussion by asking the students what happens to the food that they eat. Ask them what digestion is, where it starts and ends, and what happens to food as it travels through the digestive tract and finally what happens to the digested food as well as the undigested food. 31 Explain to the students about physical and chemical digestions. Ask the students if they know what peristalsis is and how important it is. 32 By referring to the diagram of the digestive system on p. 34, describe each part and its function. An AR model of the digestive system can be viewed by scanning the QR code given on p. 34. Get the students to answer the question in ‘Think About It’ on p. 34. 33 Ask the students why they must take good care of their teeth and how do they do so. Tell them the teeth are important for proper digestion as the first step of digestion starts in the mouth. Ask the students to reflect on what they learned before about the various types of teeth and their functions. For example, the incisors are used for biting and cutting the food, the canines help in tearing food such as meat, whereas the molars and premolars are used to crush and grind the food into smaller pieces. 34 Explain the process of digestion and the role of the enzymes in digestive juices. 35 Get the students to carry out Activity 4 to study the action of the enzyme in saliva on starch. Safety: Do not taste any solution used in the activity. 36 An animated video showing the processes that occur in the digestive tract from the mouth to the anus can be viewed by scanning the QR code given on p. 36. 37 Explain to the students what happens to the digested food in the small intestine. 38 Explain to the students what happens to the undigested food that enters the large intestine. Assessment and Evaluation 1 Assess students’ understanding of all the terms introduced by observing their participation in class discussions, whether they provide examples, scenarios, share their thoughts, or work in pairs or small groups. 2 Assess students’ research skills through their research in completing Activity 1 to 3. 3 Assess students’ scientific and critical thinking skills, attitudes and values, through observation of their participation during Activity 4 and review their results and discussions. 4 Have students complete Exercises 1−16 Workbook pp. 14–21 . Students can get extra info on reading food label, MyPlate and human digestive system via the QR code given. 5 Provide feedback to students on their performance, highlighting areas they achieved and where they need to improve. ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 17 © Praxis Publishing Singapore Pte. Ltd. Closure To summarise the important ideas and concepts taught in the lesson, consider using the key points provided through strategies such as a class discussion, a summary statement, a quiz, a visual organiser or a reflective writing assignment. Allow students to ask any additional questions for clarification or clear up any doubts. Nutrients 1 We get different types of nutrients from the food we consume: carbohydrate, protein, fat, vitamins and minerals. 2 Water is equally important to our body to carry out life processes. Carbohydrates 3 Carbohydrates, which are the main source of energy, are organic compounds made up of units of sugar molecules, known as saccharides. 4 There are two types of carbohydrates: simple carbohydrates and complex carbohydrates. 5 Simple carbohydrates consist of one sugar unit (monosaccharides) such as glucose, fructose and galactose or two sugar units (disaccharides) such as sucrose, lactose and maltose. 6 Complex carbohydrates consist of thousands of sugar units bonded together. Proteins 7 Proteins, which are needed to build new cells and repair damaged tissues in the body, are organic compounds made up of long chains of smaller molecules called amino acids. 8 Some amino acids are made in our bodies (known as non-essential amino acids) whereas others are obtained from the food we consume (known as essential amino acids). Fat 9 Fat is a source of energy and a component of the cell membrane and nerve cells. 10 Fat is an organic compound made up of glycerol and fatty acids. 11 There are three types of fat: saturated fat, unsaturated fat and trans fat. 12 Cholesterol, which is carried in the bloodstream as lipoproteins, is a combination of protein and fat found in the blood. There are two types of lipoproteins: low-density lipoproteins (LDL), also known as bad cholesterol and high-density lipoproteins (HDL), also known as good cholesterol. Vitamins 13 We need vitamins in tiny amounts to stay healthy. 14 There are two categories of vitamins: water-soluble and fat-soluble vitamins. 15 Water-soluble vitamins which are vitamins B and C cannot be stored in the body whereas fat-soluble vitamins which are vitamins A, D, E and K can be stored in the body. 16 Lack of vitamins in our diet leads to various deficiency diseases or conditions. 17 Vitamin B is mainly for the health of the nervous system. 18 Vitamin C helps to fight diseases and maintains the health of gums and mouth. 19 Vitamin A maintains healthy skin and good eyesight. 20 Vitamin D is for the healthy growth of the teeth and bones. ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 18 © Praxis Publishing Singapore Pte. Ltd. 21 Vitamin E acts as an antioxidant, helps in the production of red blood cells and strengthens the immune system. 22 Vitamin K is important for the blood clotting process. Minerals 23 We also need minerals in tiny amounts to stay healthy. 24 Lack of minerals in our diet leads to various deficiency diseases or conditions. For example, lack of calcium affects the bone and tooth formation and delays blood-clotting. Water 25 We need to consume about 2.5 litres of water daily. 26 When the intake of water is sufficient, all the life processes in the body will be carried out efficiently. A Balanced Diet 27 When we take in a balanced diet, all our nutritional and energy needs will be fulfilled. 28 MyPlate guide is the latest recommendation by the USDA (United States Department of Agriculture) regarding the portion of food groups to be consumed in each meal. 29 A nutrition facts label on packaged food product lists the types of nutrients found in the product, the serving size, and the calories per serving of the food product to enable consumers to make the right choice when selecting between food products. 30 Food is the source of energy for us to do work, grow, and repair damaged tissues. 31 The amount of energy in a food can be determined by burning a food sample in a calorimeter and measuring the amount of heat released. 32 The equation to calculate the energy value of the food sample is as follows: Energy value of food (kJ g−1) = Water mass (g) × 4.2 J g−1 °C−1 × increase in water temperature (°C) Food sample mass (g) × 1000 33 The daily energy requirement of individuals is affected by factors such as work, size or body weight, condition or state of health, climate, age, gender and physical activity of the person. Consuming Healthy Meals 34 We should consume healthy meals because they are rich in nutrients and can maintain good health. 35 We should avoid taking too much of unhealthy meals or avoid them because they have less nutritional value. They are high in fat, salt and sugar which leads to various health problems or conditions such as being overweight. Food Additives 36 Food additives are substances added into food for specific purposes. There are those which are natural and those which are synthetic. 37 Based on their usage, food additives can be classified into preservatives, colourings, sweeteners, flavourings, essence and antioxidants. (a) Preservatives are used to reduce food spoilage. (b) Colourings are used to improve the appearance of food. (c) Sweeteners are used to add sweetness to food. ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 19 © Praxis Publishing Singapore Pte. Ltd. (d) Flavourings are used to enhance food flavour. (e) Essences are used to improve the smell of food. (f) Antioxidants are used to prevent the oxidation of fatty food. 38 Some of the food additives found in processed foods are detrimental to the health when taken excessively for a long time. The Digestive System 39 Food digestion is the breakdown of food into smaller, simple and soluble molecules that can be absorbed into the bloodstream and transported to the cells in the body. 40 Digestion breaks down carbohydrates into glucose molecules, proteins into amino acids and fat into glycerol and fatty acids. 41 Digestion starts in the mouth where the teeth cuts the food into smaller pieces. The presence of food triggers the secretion of saliva containing the enzyme, salivary amylase which breaks down starch into maltose. Food is pushed along the digestive tract by peristalsis into the stomach. 42 In the stomach, pepsin, which is the digestive enzyme in gastric juice breaks down protein into polypeptides. The semi-liquid food then moves into the small intestine. 43 Duodenum, the first part of the small intestine receives the pancreatic juice secreted by the pancreas. It contains the enzymes, trypsin, lipase and pancreatic amylase. Trypsin further breaks down polypeptides into peptides. Lipase breaks down fat molecules into fatty acids and glycerol. Pancreatic amylase breaks down starch into maltose. 44 Ileum, the last part of the small intestine has glands on its wall that secretes intestinal juice that contains the enzymes, maltase, sucrase, lactase, erepsin and lipase. The final breakdown of food occurs here and the final products are fatty acids, glycerol, amino acids and glucose. 45 Jejunum and ileum of the small intestine are adapted to enable digested food to diffuse through its wall. 46 Undigested food enters the large intestine together with dead cells, fibre and water. When water is reabsorbed in the large intestine, the remaining semi-solid waste known as faeces will eventually be passed out from the body through a process called defaecation. Extension / Follow-up Activities 1 Testing food Teacher can demonstrate how food are tested on whether they contain starch, glucose (simple sugar), protein and fat. Test for glucose (Benedict’s test): For solid food samples, mix a bit of crushed food samples with water in a boiling tube to make a liquid. Add a few drops of blue Benedict’s solution to the boiling tube and heat the tube in a boiling water bath for a few minutes. Record the colour change of the content. If the food sample contains sugar, Benedict’s solution will change from blue to a red brick colour. Test for starch (Iodine test): Add a few drops of iodine solution onto a food sample and record the colour change of the solution. If the food sample contains starch, iodine solution changes colour from yellow to blue-black. ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 20 © Praxis Publishing Singapore Pte. Ltd. Test for protein (Biuret test): For solid food samples, mix a bit of crushed food samples with water in a boiling tube to make a liquid. Add several drops of blue Biuret reagant solution. Alternatively, add an equal volume of sodium hydroxide solution to the tube, followed by two drops of blue copper sulphate solution and stir it for two minutes. Record the colour of the solution. If the food sample contains protein, the colour changes to purple. Test for fat Rub the food sample on a filter paper and leave it to dry. If the food sample contains fat, the filter paper looks translucent when held up to the light. 2 Investigating the amount of sugar and salt in foods Group the students into smaller groups. Each group are asked to collect 10 food labels from their home such as food labels of biscuits, baked beans, cereals, potato chips and instant noodles. Find the amount of sugar and salt per 100 g stated on the labels and tabulate the result. Make a comparison and determine which has the highest amount of sugar and salt per 100 g. Each group will present their findings, giving the consequences of overeating sugary and salty foods. 3 Conducting an experiment to estimate the energy value of a food sample Plan your own investigation or let students carry out the following investigation in small groups. Scientific investigation worksheets: Estimate the Energy Value of a Food Sample Aim: To estimate the energy value of a food sample Materials and Apparatus: Food sample (fresh peanut or any other food of your choice), distilled water, match, boiling tube, thermometer, long pin, plasticine, retort stand with clamp, electronic balance, wind shield, measuring cylinder and Bunsen burner Procedure 1 Weigh one fresh peanut using an electronic balance and record the mass. 2 Fill one boiling tube with 20 ml of distilled water. 3 Set up the apparatus as shown below. Thermometer Retort stand Boiling tube Wind shield Distilled water Peanut Plasticine ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 21 © Praxis Publishing Singapore Pte. Ltd. 4 Record the initial temperature of the water. 5 Burn the peanut and put it as close as possible to the bottom of the boiling tube. 6 Stir the distilled water inside the boiling tube. 7 Record the temperature of the water when the peanut has stopped burning. 8 Calculate the energy value of the peanut using the following formula: Energy value of food (kJ g−1) = Water mass (g) × 4.2 J g−1 °C−1 × increase in water temperature (°C) Food sample mass (g) × 1000 4 Making a model of MyPlate Ask the students to make a model of a MyPlate, as creatively as possible. They can either draw the food in each portion on a paper plate, paste pictures of food on a paper plate or use plasticine to build the whole model. The models can then be displayed in class. The students will then understand better the proportion of the food groups that is to be consumed in each meal. Textbook Answers Think About It p.16 Bananas are usually consumed for refueling and recovery. Bananas are good source of potassium which helps muscles function well and prevent muscle cramp. Bananas help reduce inflammation to speed up recovery. Bananas are rich in carbohydrates that help replenish energy. Think About It p.17 The higher fibre content of the wholemeal bread slows down digestion, making a person feel fuller for a longer period compared to when the person consumes white bread. Think About It p.18 Compared to simple sugars with smaller molecules, complex carbohydrates which have larger molecules do not bind/fit as easily into the sweet receptors on our tongue which are responsible for the perception of taste. Think About It p.19 Babies and children need more protein for proper growth and development of their body. Athletes who train hard and build lots of muscles also need plenty of protein in their diet. Think About It p. 29 Fruit Salad – Fruit is rich with nutrients that help to increase the body’s resistance against diseases. Nasi pecel – It is high in protein and fibre. Since it is high in fibre, the fibre helps a person stay full longer and keeps the energy level high. Gado-gado – It is a complete meal providing a good balance of protein, fat and carbohydrate with lots of fibre. Since it is high in fibre, the fibre helps a person stay full longer and keeps the energy level high. Fast food – Fast food is normally high in calories, sodium and fat but low in fibre. High calories may lead to weight gain in the long run. High carbohydrate increases the blood sugar level and may lead to diabetes in the long run. High sodium content elevates blood pressure and in turn increases the risk for heart diseases. ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 22 © Praxis Publishing Singapore Pte. Ltd. Instant noodle – Instant noodles have a high salt content which leads to high blood pressure and in turn increases the risk for heart diseases. MSG in instant noodles can cause allergic reactions and hyperactivity. Sweet food – This food increases the risk for diabetes. Think About It p. 32 Salt draws water out of food, inhibiting the growth of bacteria and other microorganisms because they cannot grow and multiply without water. Think About It p. 34 Food and water will enter the lungs if there is no epiglottis. Activity 4 p. 35 Discussion: 1 For salivary amylase action, the optimum temperature is 37°C (human body temperature). 2 Starch no longer exists, only sugar exists. Saliva contains the digestive enzyme, salivary amylase which breaks down starch into maltose (simple sugar). Lesson 2.2 Circulatory System Learning Outcomes • Identify the structures and organs of the circulatory system • Describe what the circulatory system does • Recognise the components of blood and their functions • Compare the types of blood vessels • Describe the structure of the heart and how it works • Know the diseases related to the heart and blood vessels Key Understanding The circulatory system plays a major role in transporting materials such as oxygen, carbon dioxide, food and waste products to and from the cells in our body. It is a closed system because blood flows in blood vessels that are connected. The heart is a muscular organ that forces blood to move around the entire body. Induction 1 Introduce the learning outcomes of the lesson. 2 Start the discussion by asking the students what are the materials that are transported in the body and where are they transported to. For example, oxygen is transported from the lungs to the cells in the body; food is transported from the small intestine to the cells in the body; carbon dioxide (waste material) is transported from the cells to the lungs to be removed, urea (waste material) is transported from the cells to the kidneys to be removed. Teaching and Learning Activities Textbook p. 38 1 Discuss the circulatory system, which is the transport system in the body and introduce its components. ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 23 © Praxis Publishing Singapore Pte. Ltd. 2 Tell them that useful materials are transported to where they are required, and waste materials are transported to where they will be removed. Textbook p. 39 3 Explain to students that blood is the fluid in the circulatory system that transports useful and waste materials around the body. Tell them that blood has four main components: red blood cells, white blood cells, and platelets, all suspended in a liquid called plasma. Prepared human blood film slides can be viewed under the microscope for a better understanding of how the blood cells look. 4 By referring to the shape of the red blood cell shown in the diagram on p. 39, ask the students why it is shaped like that. Ask them what makes it red. 5 Tell the students that there are about 5000 times more red cells than white cells, but white cells are mainly bigger. Ask them if they know the function of the white blood cells. 6 Explain to the students the importance of platelets in preventing blood loss from wounds. Textbook pp. 40-41 7 The blood travels in a closed system and always remains within blood vessels. Introduce to the students the three types of blood vessels: arteries, veins and capillaries. 8 Discuss the differences between arteries, veins and capillaries by showing students a thick-walled rubber tube to represent an artery, a thin-walled tube to represent a vein and a fine microtube to represent a capillary. Talk about their functions as well and the colour of the blood in them. The blood carried by arteries from the heart is bright red as it is rich in oxygen while the blood carried by veins back to the heart is dull red as it is rich in carbon dioxide. 9 Explain to them why arteries have thicker walls compared to veins. The blood in arteries flows under high pressure from the heart while the blood in veins flows at low pressure back to the heart. That is why blood loss is much greater from a cut artery than from a cut vein. 10 Talk about pulse. Arteries have a pulse due to the force of the heartbeat while veins do not have a pulse. Most arteries are found deep in the body, but there are some which are closer to the surface and here the pulse can be felt. 11 Stress that veins have valves which ensure blood flows only one way, which is towards the heart. At times, the walls of the veins can become stretched and less elastic, causing the valves to weaken and unable to function properly. This can cause the blood to flow backwards and collect in the veins. The veins will then be swollen and become varicose veins. Show the students a picture of a person with varicose veins. Textbook pp. 41-44 12 Start off the discussion by playing a recording of a beating heart for the students to listen. Ask the students what is the sound they just heard. Ask the students to show where their heart is. Then ask them the role of the heart. 13 Explain the circulation of blood in the heart by referring to the diagram shown on p. 42. 14 An animated video showing the blood flow in the heart can be viewed by scanning the QR code given on p. 42. Both sides of the heart pumping in unison explain the double circulatory system, in which the heart pumps the blood twice - once to the lungs, known as the pulmonary circulation and once to the body, known as the systemic circulation. ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 24 © Praxis Publishing Singapore Pte. Ltd. 15 Get the students to carry out Activity 5 to compare the heart rate per minute when a person is at rest and after the person exercises. Students will get a better understanding on how to take the pulse and then, calculate the heart rate per minute. Show students how to feel the pulse in their wrist. Explain to them that the pulse rate (or the heart rate) is the number of times the heart beats per minute. 16 Ask students what happens to their heart rate when they jog, and when they stop jogging. Jogging increases the heart rate because the heart pumps faster to carry food and oxygen to the muscles and to carry away the waste materials being produced by the muscles. When they stop jogging, gradually the heart rate decreases. The faster the heart rate goes back to its resting heart rate, the fitter the person. 17 Get the students to answer the question in ‘Think About It’ on p. 44. 18 Tell the students the resting heart rate in an adult and in a baby varies. In an adult, the heart rate is about 70 beats per minute, whereas in a baby it is probably nearly twice as fast. Ask the students why is that so? This is because their rapid growth requires energy, therefore food is burned in every cell of their bodies to produce energy to fuel that growth. 19 Explain to students that any defect in the heart can cause serious health problems. For example, a hole in the heart, in which there is a gap between the right and left sides of the heart, usually between the auricles causes oxygenated and deoxygenated blood to mix, therefore the cells in the body receive less oxygen. 20 Go through the ‘Science Facts’ on p. 44 with the students about blood pressure. Textbook pp. 44−45 21 Start the discussion by asking students to name several diseases related to the heart and blood vessels. Ask them if any of their family members suffer from those diseases. Let them know that cardiovascular diseases are responsible for so many deaths worldwide annually and according to WHO, an estimation of 17.9 million people lose their lives each year. 22 Go through the examples of cardiovascular diseases given on pp. 44-45. Describe how a poor diet can lead to these diseases. 23 Get the students’ opinion on how to ensure their heart keeps working properly. Ask the students to come up with some basic rules to keep their heart healthy to avoid cardiovascular diseases. For example, exercising regularly, not smoking tobacco, reducing salt in diet, reducing fatty food, avoiding alcohol and eating more fruits and vegetables are some of the ways to reduce the risk of cardiovascular diseases. 24 Encourage the students to research using the internet to obtain YouTube videos to see how a heart transplant surgery is carried out. Suggestion: https://youtu.be/o1z2DfFZBS4 25 Introduce to them the term pacemaker. Ask the students to get more information on the pacemaker and the purpose of using it by using the Internet. Note: Our heart is controlled by a natural pacemaker called sinoatrial node. Sometimes when the sinoatrial node fails to function properly, an artificial pacemaker is used to restore the normal heart rate. It is a small device that runs on battery implanted in the chest. It helps to control the heartbeat of the individual. ©Praxis Publishing_Focus On Science

Teacher’s Guide Focus-on Science Grade 8 25 © Praxis Publishing Singapore Pte. Ltd. Assessment and Evaluation 1 Observe how students participate in class discussions and activities. 2 Assess students’ scientific and critical thinking skills, attitudes and values, through observation of their participation during Activity 5 and review their result, discussion and conclusion. 3 Have students complete Exercises 1−11 Workbook pp. 21−26 . Students can get extra info on human heart via the QR code given. 4 Provide feedback to students on their performance, highlighting areas they have achieved and where they need to improve. Closure To summarise the important ideas and concepts taught in the lesson, consider using the key points provided through strategies such as a class discussion, a summary statement, a quiz, a visual organiser or a reflective writing assignment. Allow students to ask any additional questions for clarification or clear up any doubts. Blood 1 The human blood is a renewable living tissue which consists of 55% plasma and 45% blood cells (red blood cells, white blood cells and platelets). 2 Plasma which is mainly made up of water, holds all the blood cells together. It helps to transport nutrients, hormones and other important substances around the body and transport waste materials to be removed from the body. 3 Red blood cells carry oxygen around the body. 4 White blood cells defend the body against diseases. 5 Platelets helps to clot blood on wounds. Blood Vessels 6 There are three types of blood vessels: arteries, veins and capillaries. 7 Arteries branch into smaller blood vessels known as arterioles, which in turn branch into extremely large numbers of smaller blood vessels known as capillaries. Capillaries join to form bigger blood vessels known as venules which will then join to form veins. 8 Arteries carry blood from the heart to the entire body. 9 Veins carry blood back to the heart. 10 Capillaries are a network of tiny blood vessels connecting the arteries to the veins. Heart 11 The heart is an organ with its wall made up of cardiac muscle. 12 There are four chambers in the heart. The two upper chambers are called auricles or atria (singular: atrium) and the two lower chambers are called ventricles. 13 The right-hand side of the heart receives deoxygenated blood rich in carbon dioxide from around the body and pumps it into the lungs. 14 The left-hand side of the heart receives oxygenated blood rich in oxygen from the lungs and pumps it around the body. 15 The atria receive blood that returns to the heart while the ventricles pump blood out of the heart. ©Praxis Publishing_Focus On Science