(ii) State the function of the structure stated in question 1(a)(i). (iii) List the characteristics of the structure stated in question 1(a)(i). (b) What will happen if the structure in question 1(a)(i) experiences an injury? (c) State the difference between tendon and ligament. 2. Photograph 1 shows a moving earthworm. Photograph 1 (a) What type of skeleton does the earthworm have? (b) The earthworm moves with the aid of two types of muscles. Name the types of muscles. (c) Explain how the muscles in the body of the earthworm cause movement. 3. Photograph 2.1 shows a giraffe drinking water. Photograph 2.1 (a) (i) Based on Photograph 2.1, state the way the giraffe stands while it is drinking water. (ii) How can this stabilise the giraffe? (b) Photograph 2.2 shows two types of animals, X and Y. X Y Photograph 2.2 140
(i) If both animals have the same mass, which animal is more stable. (ii) Explain your answer in question 3(b)(i). (iii) Suggest a posture when animal Y is more stable. 4. Woody plants have roots such as the buttress roots, prop roots and stilt roots to add support. Based on the statement above, describe the way woody plants can stabilise their position without falling due to strong wind. Mind Challenge Challenge 5. Photograph 3 shows a whale stranded on the beach. Photograph 3 (a) Based on your knowledge about the support system of whales, can the whale return to the sea on its own? (b) Explain your answer. 141 Support, Movement and Growth Chapter 6
Body Coordination Endocrine system Endocrine glands Hormones Hormone imbalance Effects of drug abuse Effects of alcohol abuse Healthy mind Keywords 7 Chapter 142
Hormone Treatment Menopause is a condition when the ovaries stop producing ova (egg) and the woman stops menstruating. This condition usually happens to women aged 45 to 55 years. During menopause, the hormone oestrogen in the body decreases thus producing symptoms such as difficulty in sleeping, muscle and joint pain and restlessness. Hormone replacement therapy (HRT) treatment is believed to be able to overcome menopausal symptoms. HRT can be done in the form of Oestrogen-Progestin therapy (EPT) if the woman concerned still has a uterus, or Oestrogen therapy (OT) for those who have undergone uterus removal surgery. HRT is aimed at restoring the hormone levels of women to allow their bodies to function normally again by replacing the decreasing hormones during menopause. Anda akan belajar tentang: human endocrine system disruptions to body coordination healthy mind Digest Science What are the endocrine glands in the human body? What is the importance of hormones? What are the effects of drug and alcohol abuse on body coordination? What is the importance of a healthy mind? You will learn about: Source: myMetro Body Coordination Chapter 7 143
7.1 Human Endocrine System 7.1.1 The endocrine system functions as a messenger to the whole body that uses hormones. Hormone is a type of chemical substance secreted by special glands known as the endocrine glands. These glands are ductless glands because the hormone is not carried through a duct but secreted directly into the blood circulatory system to be distributed to the whole body. A type of hormone can have more than one target organ (organ that responds to the hormone). Run away The endocrine gland secretes hormones that cause an increase in: (a) heartbeat (b) rate of breathing (c) blood pressure (d) blood glucose level (e) rate of metabolism Endocrine System and Its Functions The human body has a system known as the endocrine system. The endocrine system is one of the systems in the body that coordinates body functions that involve chemical substances. How would you feel if you came across a snake while playing at the field? Would you run away? Why does this happen? The answer is simple. This is to save yourself from harm. Let us see the situation below. When a snake is seen ... Effects: • The heart pumps more blood to provide more oxygen and glucose to the muscles • The muscles obtain more energy • More stored glycogen is converted into glucose Figure 7.1 Example of a situation that involves the endocrine system 144
Blood vessels Target organ cells Hormones Endocrine gland cells Blood stream 7.1.1 Figure 7.2 shows the way the hormone coordination acts. Figure 7.2 Method of action of hormone coordination A ductless gland Coordinates the activity of the body by responding to the stimulus from the environment Target organ Has a suitable receptor that is able to recognise and respond to the specific hormone A type of protein Stimulates the functions of specific tissues or organs Has prolonged effect A slow response Secreted in small quantities Endocrine gland Hormones secretes carried through blood circulation is functions Body Coordination Chapter 7 145
Figure 7.3 Endocrine glands in humans 7.1.1 Figure 7.3 shows the main endocrine glands and their position in the body. Interactive Game Pituitary gland Pituitary gland is located below the cerebrum. This gland is also known as the master gland because it produces hormones that control other endocrine glands. Pituitary gland Women have a pair of ovaries in the pelvic space. Ovary Ovaries 146
7.1.1 Adrenal glands are located above the kidneys. Adrenal glands The thyroid gland is located in front of the trachea. Thyroid gland The pancreas is located at the back of the stomach. Pancreas Men have a pair of testes protected by a scrotum. Testis Thyroid gland Testis Pancreas Kidney Adrenal glands Body Coordination Chapter 7 147
7.1.1 Table 7.1 Functions of hormones released by the endocrine glands Endocrine gland Hormone Function Pituitary gland Antidiuretic hormone (ADH) • Controls the quantity of water reabsorbed by the kidneys Growth hormone (GH) • Stimulates growth in children • Maintains healthy body composition in adults • Maintains the muscle and bone mass of adults Thyroid gland Thyroxine • Controls the rate of metabolism • Controls the physical and mental development in children Adrenal gland Adrenaline • Prepares your body to act in an emergency situation by: − increasing the rate of metabolism − increasing the rate of heartbeat − increasing the glucose level in the blood − dilating the size of the pupil Pancreas Insulin • Controls the glucose level in the blood by converting excess glucose into glycogen to be stored in the liver Ovary Oestrogen • Controls the female secondary sexual characteristics such as development of breasts and broadening of the hip • Stimulates the production of ova • Prepares the uterus for implantation of embryo Progesterone • Maintains the thickness of the wall of the uterus for the implantation of embryo Testis Testosterone • Controls the development of male secondary sexual characteristics such as a deep voice and the growth of moustache • Stimulates sperm production Table 7.1 shows the function of hormones released by the endocrine glands. 148
Aim: To carry out a study on endocrine gland disorder. Instructions: 1. Carry out this activity in groups. 2. Gather information from the Internet, reference books, magazines and articles on the causes and effects of the following: (a) Diabetes insipidus (b) Diabetes mellitus (c) Acromegaly (d) Low rate of metabolism 3. Appoint a student to role play as a ‘doctor ‘. 4. The ‘doctor’ will answer all the questions asked by other students. ... ... Activity 7.2 Causes and Effects of Hormonal Imbalance Hormone is an organic chemical substance that has an important role in every function of the body. Hence, the rate of hormone secretion must be balanced with its functions. Over secretion and under secretion of hormone by the endocrine glands will cause hormonal imbalance that leads to diseases. These could be due to an unhealthy lifestyle or exposure to dangerous rays. Aim: To prepare a multimedia presentation that shows the main endocrine glands (pituitary gland, thyroid gland, adrenal gland, pancreas, ovary and testis) and their functions. Instructions: 1. Carry out this activity in groups. 2. Gather information from the Internet, reference books, magazines and articles on: (a) position of the endocrine glands (b) type of hormones secreted (c) function of each hormone 3. Present the outcome of your group discussion in class in the form of a multimedia presentation. Activity 7.1 Result Showcase Hot Seat 7.1.1 7.1.2 21st Century Skills 21st Century Skills Body Coordination Chapter 7 149
Thyroxine deficiency will cause: • low rate of metabolism • inability to tolerate cold • stunted physical and mental development in children (cretinism). • less energy in adults (myxedema) • tendency to become fat • goitre Excessive thyroxine hormone will cause: • high rate of metabolism • sweating and always feeling hot • sleeping difficulties and a very good appetite • tendency to become thin • thyroid gland enlargement , protruding eyeballs and swollen neck Hormonal Imbalance Oestrogen deficiency will cause: • development of female secondary sexual characteristics to be disrupted. Excessive oestrogen will cause: • female characteristics in men Photograph 7.1 Goitre 7.1.2 Progesterone deficiency will cause: • menstrual problems • headache • constipation • miscarriage How Can I Balance My Hormones http://bukutekskssm.my/ Science/F4/Pg150 INFORMATION Testosterone hormone deficiency will cause: • delay in reaching puberty • low sperm count Excessive testosterone hormone will cause: • male characteristics in women 150
Growth hormone deficiency will cause: • dwarfism Excessive growth hormone will cause: • uncontrolled growth • acromegaly (gigantism) Antidiuretic hormone (ADH) deficiency will cause: • poor reabsorption of water at the collecting duct in the kidney • excessive production of urine • excessive thirst • diabetes insipidus Excessive antidiuretic hormone (ADH) will cause: • headache • dizziness Insulin hormone deficiency will cause: • failure of excessive glucose to be converted to glycogen • increase in blood glucose level • diabetes mellitus Excessive insulin will cause: • low glucose levels • hypoglycaemia • excessive thirst Photograph 7.2 Acromegaly man (right) and normal man (left) 7.1.2 Body Coordination Chapter 7 151
7.2.1 Formative Practice Formative Practice 7.1 1. State the meaning of hormone. 2. State the main endocrine glands in the human body. 3. Name the hormones secreted by the following glands: (a) Adrenal gland (b) Pancreas (c) Testis (d) Thyroid gland 4. What is the function of the hormones produced by the following glands? (a) Thyroid gland (b) Ovary (c) Pancreas 7.2 Disruptions to Body Coordination Body coordination can be disrupted due to various factors. One of the main factors is the uncontrolled consumption of drugs. Drugs are chemical substances that can disrupt the neuron function by delaying the impulse transmission in the neuron. The drugs that are taken without control disrupts body coordination, and causes addiction. Photograph 7.3 Types of drugs used as medicine 152
Types of Drugs Drugs may cause good or bad effects on the body depending on its use. Drugs can be used to treat a disease. Morphine and steroid need to be taken under a doctor’s supervision. Figure 7.4 shows the types of drugs and their effects. 7.2.1 Figure 7.4 Types of drugs and their effects Depressant • Prevents or slows down impulse transmission in body coordination. User will be sleepy and less anxious. The effect also depends on the dosage taken • Examples are barbiturates and alcohol Stimulant • Speeds up impulse transmission in body coordination. User will feel very confident and alert to the surroundings • Effect also depends on the dosage taken • Examples are amphetamine and methamphetamine Inhalant • Chemical substances that can be inhaled through breathing • Causes hallucination • Damages the brain, lungs and kidneys • Examples are solvent and gas substance (Source: http://www.adk.gov.my/en/ public/posters-banners) (Access on 19 August 2019) Hallucinogen • Changes the path of impulses in the brain • Causes hallucination, affects perception • Affects muscle coordination • Causes hearing of voices and seeing objects that are non-existent • Examples are ketamine and LSD (lysergic acid diethylamide) Types of drugs National Anti-Drugs Agency http://bukutekskssm.my/ Science/F4/Pg153 INFORMATION Body Coordination Chapter 7 153
7.2.2 Drug abuse causes addiction and addicts will experience withdrawal symptoms if they cease to take drugs. The symptoms include shivering, nausea, anxiety and depression. Figure 7.5 shows the effects of drug abuse on body coordination. Figure 7.5 Effects of drug abuse Heartbeat, rate of breathing, blood pressure Heartbeat, rate of breathing, blood pressure Nervous System Drugs More energetic, active, indecisive and aggresive Disruptions to perception, hallucination and illusion Slow response to stimulus, sleepiness and weak muscle coordination causes effect stimulates slows down The factors that cause drug abuse are curiosity, peer influence, seeking pleasure and the desire to overcome sadness or to forget a problem. Aim: To prepare a review on drug abuse. Instructions: 1. Carry out this activity in groups. 2. Listen and record important information on drug abuse such as: (a) drug categories (b) types of drugs and examples of each type of drug (c) effects of drug abuse (d) characteristics of drug addicts 3. Gather information obtained and prepare a review. 4. Display your group’s review to the class. 5. Write comments about the work of other groups. ... ... Activity 7.3 Gallery Walk 21st Century Skills 154
EN. HARIZ EN. HARIZ HARIS Effects of Drug and Alcohol Abuse on Body Coordination Most drugs influence the body coordination by causing an effect on the nervous system. Alcohol also affects the nerves by slowing the flow of nerve impulses. Hence, affecting the brain function. Let us look further at the effects of drug and alcohol abuse on our body coordination. Hormonal imbalance • The body will experience coordination disruption. The body will be exposed to danger and injury. The body will either experience extreme growth or no development if damage to the pituitary gland happens. Secondary sexual development will be stunted if oestrogen and testosterone hormones fail to function normally. • Symptoms of hormonal imbalance can be observed through physical and mental changes of the person such as excessive height and size, weight loss, depression and poor memory. Unclear speech • Consuming alcohol will cause negative effects on parts of cerebrum in the brain. • Excessive alcohol consumption causes unclear speech. Slow reflex action • Psychoactive chemical substances in drugs and ethanol in the alcohol will slow down the response of the nervous system. These chemical substances will be present between the afferent neurons and interneurons. The impulse transmission will be blocked and the process of impulse transmission to the brain will slow down. • This can be observed in drug addicts and in those who consume alcoholic drinks excessively. 7.2.2 Loss of balance • Consuming drugs and alcoholic drinks will cause weak muscle coordination resulting in staggering and loss of balance. Body Coordination Chapter 7 155
CHEONG • Continuous consumption of large amounts of alcoholic drinks, and drug abuse can cause toxic effects on the liver resulting in liver cirrhosis. • Liver cirrhosis is the condition of the liver that undergoes chronic damage, scarring, hardening and failure to function normally. This scar will spread slowly until the liver functions are lost completely. Effects of Drug and Alcohol Abuse on Physical and Mental Health Besides influencing the nervous system, drug abuse also causes many physical and mental health problems such as liver damage, weak immune system, brain damage and serious mental problems. Excessive consumption of alcoholic drinks can also damage most organs of the human body. Let us look at the effects of drug and alcohol abuse on human health. Photograph 7.4 Difference between a healthy liver and liver cirrhosis Liver cirrhosis 7.2.2 (a) Healthy liver (b) Liver cirrhosis 156
Formative Practice Formative Practice 7.2 1. What is the effect of drug abuse on body coordination? 2. How do the chemical substances in the drugs and alcoholic drinks affect the neurons? 3. How do drugs and alcohol influence hormone secretion? • Consuming drugs such as amphetamine will activate brain cells and increase the rate of metabolism. The user will become more active, be unable to sleep, violent and aggressive. • A person who consumes alcohol excessively can become drunk and lose his senses, laugh alone, act out of control and become violent. Violent behaviour • Drugs such as marijuana disrupts the brain function. This drug will change a person’s perception. • This causes the person to experience hallucination, paranoia or suspicious feeling and fear of others. Hallucination may also cause aggressive behaviour towards other people. Hallucination • Alcohol can cause stomach ulcer. • Stomach ulcer or peptic ulcer is a condition in which the lining of the stomach is injured. • This is because alcohol causes the stomach to produce more acid than normal which will cause irritation and inflammation of the stomach lining. • The patient will complain of heartburn or pain at the upper liver region, bloatedness, nausea and vomiting. • A patient with stomach ulcer can also experience more serious symptoms such as vomiting blood and passing out black stools. Stomach ulcer Photograph 7.5 Ulcer in the stomach 7.2.2 Body Coordination Chapter 7 157
7.3 Healthy Mind In the world of advancement in science and technology, we are often shocked by society’s neglect in keeping a healthy mind. The mind is the brain function that relates to our consciousness, personality, thinking, memory, judgement, intellect and emotion. A healthy mind has the ability to reason and think as well as to make logical judgements before an action is taken. A healthy mind also refers to positive behaviour, independence, ability to care for others and being responsible. 7.3.1 Characteristics of individuals who have healthy minds: Can think and make judgements Able to differentiate between right and wrong Able to detect stimulus and respond accordingly Responsible Open-minded and not emotional Can recall past events that are sad or happy Live in peace and have a positive view on life Able to reason Dare to accept challenges Free from prejudice 158
There are several factors that can influence the mind and mental health. Figure 7.6 shows factors that influence the mental health. Figure 7.6 Factors that influence mental health Hormonal imbalance during menstruation, premenstrual syndrome and post-menopause Excessive consumption of alcoholic drinks Injury to the part of the brain as a result of microorganism/ pathogen infection, accident or tumour Mental stress Aging Drug abuse (a) Normally, hormonal imbalance happens before or during the menstrual cycle and also during menopause. Usually, a person will experience headache, depression and is easily irritated. (b) Excessive consumption of alcoholic drinks will disrupt a person’s ability to think, detect stimulus, reason and control emotions. A person who is drunk can become aggressive and endanger himself or other people. (c) Drug abuse has negative effects such as the failure to fulfil responsibilities towards the family, work or studies and others. Drug abuse can also cause serious mental problems. (d) Mental stress can affect a healthy mind. Hence, we need to be able to manage stress so that it does not affect the mind. (e) Brain injury can cause a person to lose his memory or intellectual ability. Brain injury can also cause a person to be easily influenced by emotions. 7.3.1 Factors that influence the mental health Body Coordination Chapter 7 159
Each individual must have a healthy mind. This is because each individual has a responsibility towards his family, place of work, society and country. Society • Learn to handle constructive criticisms • Can play a role as a friend to exchange ideas • Help people in need Family • Can build a happy family • Make wise decisions • Become a role model in the family Country • Think positive • Practise religious and moral values • Practise a healthy lifestyle • Generate the economy of the country Place of work • Forge a good relationship between employees and employers • Forge a good relationship among colleagues • Produce quality work • Be disciplined Photograph 7.6 Importance of having a healthy mind 7.3.1 160
Aim: To evaluate the importance of having a healthy mind in the family, workplace, society and country. Instructions: 1. Carry out this activity in groups. 2. Prepare a poster to explain the importance of a healthy mind to other students in the school. 3. Display the poster in the exhibition corner of the class. ... ... Activity 7.5 Formative Practice Formative Practice 7.3 1. What is meant by the mind? 2. List five characteristics of a healthy mind. 3. Explain how hormonal imbalance can affect the mind. 4. State three factors that influence mental health. PAK-21 Melukis Poster Aim: To gather information on a healthy mind and its importance. Instructions: 1. Carry out this activity in groups. 2. Gather information from magazines, books, newspapers or the Internet on the following: (a) factors that influence a healthy mind (b) how these factors influence the mind (c) the importance of having a healthy mind 3. Present the outcome of your group discussion in the class in the form of a multimedia presentation. Activity 7.4 Result Showcase Draw a Poster 7.3.1 21st Century Skills 21st Century Skills Body Coordination Chapter 7 161
Factors that influence the mind BODY COORDINATION Disruptions to Body Coordination Healthy Mind Human Endocrine System Endocrine glands Hormones • Diabetes insipidus • Diabetes mellitus • Acromegaly • Low rate of metabolism Functions Causes and effects of hormonal imbalance on health Excessive consumption of alcoholic drinks Drug abuse Effects of drugs and alcohol abuse on body coordination and mental health secrete 162
Summative Practice Summative Practice 7 After studying this chapter, you are able to: 7.1 Human Endocrine System Explain the endocrine system and its functions. Explain with examples the causes and effects of hormonal imbalance on health. 7.2 Disruptions to Body Coordination Explain with examples the types of drugs. To understand and draw conclusions on the effects of drugs and alcohol abuse on body coordination and mental health. 7.3 Healthy Mind Justify the importance of having a healthy mind in a community. Self-reflection Self-reflection 1. Figure 1 shows the human endocrine system. P Q R S Figure 1 (a) State the gland that is the master gland in the human endocrine system. (b) (i) Name the hormone secreted by gland Q. (ii) State the effect on humans if the hormone in question 1(b)(i) is not adequately secreted into the body. Objective Questions http://bukutekskssm.my/ QUIZ Science/F4/Q7 Body Coordination Chapter 7 163
(c) (i) Name gland R. (ii) State the hormone secreted by gland R. (iii) How can the failure of gland R cause a person to have diabetes mellitus? (d) Name the hormone secreted by gland S. 2. Figure 2 shows a part of the endocrine system of a woman. Y Figure 2 (a) (i) Name the hormones produced by gland Y. (ii) State one function for each hormone that is stated in question 2(a)(i). (b) Although gland Y exists since birth, the gland is inactive. When will gland Y become active? (c) (i) Name the endocrine gland for man that is also inactive during birth. (ii) Explain the function of the hormone that is secreted by the gland that you have stated in question 2(c)(i). Mind Challenge Challenge 3. Drinking coffee excessively is not good for health. Explain the reason. 4. A woman who is pregnant is found to be an alcoholic. What will happen to the foetus in the uterus? 5. Your friend told you that she feels stressed because of family problems. As a friend, what can you do to help her? 164
Exploration of Elements in Nature Exploration of Elements in Nature 165 • There are 118 elements that have been discovered. Do you know the position of carbon in the Modern Periodic Table of Elements? • The windows of skyscrapers in Malaysia are usually made of glass. What are the other uses of glass? • If you were sick, the doctor would treat and give you the appropriate medicine. What would happen if we took medicine without the advice of doctors? 3THEME
8 Elements and Substances Atomic substances Molecular substances Ionic substances Modern Periodic Table of Elements Positive ions Negative ions Isotopes Keywords Chapter 166
What type of particles are found in gold? How are the elements arranged in the Modern Periodic Table of Elements? How are the positive and negative ions formed from atoms? What is an isotope? Elements in the Universe and Earth Hydrogen and helium are the most abundant elements in the Universe. The stars including the Sun consist of hydrogen and helium. On Earth, there are elements such as oxygen, silicon and gold. Oxygen allows all living things to exist on Earth. Digest Science Anda akan belajar tentang: matter Modern Periodic Table of Elements isotope You will learn about: Elements and Substances Chapter 8 167
8.1 Matter Atomic Substances, Molecular Substances and Ionic Substances You learned that matter consists of tiny and discrete particles in Form 1. Matter is formed by three types of particles namely atoms, molecules or ions. backack An atom consists of subatomic particles, which are protons, neutrons and electrons. - Electron - Proton - Neutron – + – – – – – – + + + + + + Figure 8.1 Atomic substances Gold metal Balloons filled with helium Gold atoms Helium atoms 8.1.1 Atom The atom is the smallest particle of an element. It is the most basic unit in an element. Molecule A molecule consists of two or more atoms which are chemically combined. Molecules can be the combination of the same or different types of atoms. Ion An ion is a charged particle, either positively-charged or negatively-charged. An ion is formed when an atom loses or gains electrons. All the substances around us are matter. The substances can be classified into three groups based on the type of particles they contain. Atomic Substances These substances contain only atoms. All metals and inert gases are made up of atoms. Atoms in metals are arranged in a neat and orderly manner, while atoms in inert gases are spread far apart with no regular arrangement. 168
The ionic substances are formed by the reaction between the metal elements and non-metal elements. These substances contain positive ions and negative ions. An example of ionic substance is sodium chloride. Figure 8.2 Molecular substances Figure 8.3 Ionic substances Activity 8.1 Aim: To create a multimedia presentation on materials that are made of atoms, molecules and ions in daily life. Instructions: 1. Gather information from various sources on the materials around you that are made up of atoms, molecules and ions. 2. Present the information gathered in the form of multimedia presentation. Result Showcase Oxygen molecules Water molecules + – + + – + – + – + – + – + – + – + + – + Sodium ions and chloride ions Oxygen tank Common salt Sea water 8.1.1 Molecular Substances These substances contain molecules made up of two or more atoms that combined chemically. The atoms can either be the same or different. Most of the non-metal substances exists in the form of molecules. The reaction between the non-metallic elements forms a compound which exists in the form of molecules. Ionic Substances 21st Century Skills Elements and Substances Chapter 8 169
Existence of Elements in Various Forms Do you still remember the elements in the Modern Periodic Table of Elements that you studied in Form 1? Elements can exist in the form of atoms, molecules or ions. Can the same elements exist in different forms? Take a look at the photograph below. Photograph 8.1 Rusty hammer and non-rusty hammer Photograph 8.2 Lime juice and air Formative Practice Formative Practice 8.1 1. Give three types of particles that make up a substance. 2. State an example of a substance that is made up of iron in the form of ions. 3. Classify the following substances according to the type of particles that they are made up of either atoms, molecules or ions. Iron sheets, ice cubes, common salt, sugar cubes, marbles, copper wire, limewater, oxygen gas, helium gas 4. Give two examples of elements that exist in the form of molecules and atoms. – – + – + + 8.1.2 Iron exists in the form of atoms in the head of a hammer. Hydrogen exists in the form of molecules in the air. Hydrogen exists in the form of ions in the lime juice. Element: Iron Element: Hydrogen – + – – + – + – + – + – + – + – + – – + – Iron exists in the form of ions in rust. 170
8.2 Modern Periodic Table of Elements In Form 1, you learned about 118 types of elements listed in the Modern Periodic Table of Elements. Now, let us study the Modern Periodic Table of Elements shown in Figure 8.4 carefully and identify several important features about it. Moving from left to right across a period, there is a gradual change in chemical and physical properties, such as: (a) a decrease in metallic properties and an increase in non-metallic properties (b) a change of the properties of oxides from basic to acidic (c) a decrease in electrical conductivity of the element Transition metals 1 HHydrogen 1 1 H Hydrogen 1 3 Li Lithium 7 4 Be Beryllium 9 11 Na Sodium 23 12 Mg Magnesium 24 19 KPotassium 39 20 Ca Calcium 40 37 Rb Rubidium 85.5 38 Sr Strontium 88 55 Cs Caesium 133 56 Ba Barium 137 87 Fr Francium 88 Ra Radium 105 Db Dubnium 106 Sg Seaborgium 107 Bh Bohrium 108 Hs Hassium 109 Mt Meitnerium 110 Ds Darmstadtium 111 Rg Roentgenium 112 Cn Copernicium 21 Sc Scandium 45 39 YYttrium 89 22 Ti Titanium 48 40 Zr Zirconium 91 72 Hf Hafnium 178.5 23 VVanadium 51 41 Nb Niobium 93 73 Ta Tantalum 181 24 Cr Chromium 52 42 Mo Molybdenum 96 74 Tungsten W 184 25 Mn Manganese 55 43 Tc Technetium 75 Re Rhenium 186 26 Fe Iron 56 44 Ru Ruthenium 101 76 Os Osmium 190 27 Co Cobalt 59 45 Rh Rhodium 103 77 Ir Iridium 192 28 Ni Nickel 59 46 Pd Paladium 106 78 Pt Platinum 195 29 Cu Copper 64 47 Ag Silver 108 79 Au Gold 197 30 Zn Zinc 65 48 Cd Cadmium 112 80 Hg Mercury 201 31 Ga Galium 70 49 In Indium 115 81 Tl Talium 204 113 Nh Nihonium 114 Fl Flerovium 115 Mc Moscovium 116 Lv Livermorium 117 Ts Tennessine 118 Og Oganesson 32 Ge Germanium 73 50 Sn Tin 119 82 Pb Lead 207 33 As Arsenic 75 51 Sb Antimony 122 83 Bi Bismuth 209 34 Se Selenium 79 52 Te Tellurium 128 84 Po Polonium 210 35 Br Bromine 80 53 I Iodine 127 85 At Astatine 210 36 Kr Krypton 84 54 Xe Xenon 131 86 Rn Radon 222 5 BBoron 11 13 Al Aluminium 27 6 CCarbon 12 14 Si Silicon 28 7 NNitrogen 14 15 PPhosphorus 31 8 OOxygen 16 16 SSulphur 32 9 FFluorine 19 17 Cl Chlorine 35.5 2 He Helium 4 10 Ne Neon 20 18 Ar Argon 40 58 Ce Cerium 140 90 Th Thorium 232 57 La Lanthanum 139 89 Ac Actinium 59 Pr Praseodymium 141 91 Pa Protactinium 231 60 Nd Neodymium 144 92 UUranium 238 61 PmPromethium 145 93 Np Neptunium 62 SmSamarium 150 94 Pu Plutonium 63 Eu Europium 152 95 AmAmericium 64 Gd Gadolinium 157 96 CmCurium 65 Tb Terbium 159 97 Bk Berkelium 66 Dy Dysprosium 162.5 98 Cf Californium 67 Ho Holmium 165 99 Es Einsteinium 68 Er Erbium 167 100 FmFermium 69 TmThulium 169 101 Md Mendelevium 70 Yb Ytterbium 173 102 No Nobelium 71 Lu Lutetium 175 103 Lr Lawrencium Proton number Metal Semi-metal Non-metal Symbol of element Name of element Relative atomic mass 104 Rf Rutherfordium 57 – 71 Lanthanoids 89 – 103 Actinoids Solid Liquid Gas Key: GROUP C Br H Lanthanoids Actinoids 1 1 Alkali metals 2 2 3 3 4 4 5 5 6 6 7 7 8 9 10 11 12 13 14 15 16 17 18 Alkaline earth metals Halogens Inert gases Each of the vertical columns in the Modern Periodic Table of Elements is called a group. There are 18 groups in the Modern Periodic Table of Elements. Each of the horizontal rows of element is called a period. There are 7 periods in the Modern Periodic Table of Elements. There are two series of elements with the proton numbers of 57 to 71 and 89 to 103 placed separately at the bottom of the Modern Periodic Table of Elements. These two series are known as lanthanoids and actinoids. 8.2.1 8.2.2 Figure 8.4 The Modern Periodic Table of Elements PERIOD The Principle for the Arrangement of the Elements in the Modern Periodic Table of Elements In the Modern Periodic Table of Elements, the elements are arranged from left to right and top to bottom, in the order of their increasing proton number. Proton number is defined as the number of protons in the nucleus of an atom. Study the Modern Periodic Table of Elements again. Elements and Substances Chapter 8 171
Aim: To relate the arrangement of the elements with their proton number in the Modern Periodic Table of Elements. Instructions: 1. Carry out this activity in groups. 2. Each group is given an incomplete Modern Periodic Table of Elements and several cards with the symbol and proton number of the element. 3. Use the cards to fill in the blank space in the Modern Periodic Table of Elements given. 4. Present the completed Modern Periodic Table of Elements in front of the class. Aim: To identify the position of the element in the Modern Periodic Table of Elements. Instructions: 1. Carry out this activity in groups. 2. Refer to the Modern Periodic Table of Elements and determine the exact symbol of the element below and their position in the Modern Periodic Table of Elements. V 7 18 20 42 14 40 40 96 W X Y 3. Present the results in front of the class. ... ... ... ... 8.2 8.3 Activity Activity Round Table Round Table Electron Arrangements of the Elements Now, you know that every element in the Modern Periodic Table of Elements has a specific proton number. For example, the proton number of oxygen is 8 and the proton number of magnesium is 12. For a neutral atom, the number of protons is equal to the number of electrons. How are the electrons arranged around the nucleus? The electrons are arranged in shells around the nucleus. The electrons occupy the shells closest to the nucleus first. The electrons can only start occupying a new shell when the previous one has been occupied. 8.2.2 8.2.3 S Sulphur has a proton number of 16. Hence, a sulphur atom has 16 electrons. These electrons are arranged as two in the first shell, eight in the second shell and the remaining six in the third shell. The electron arrangement of the sulphur atom can be written as 2.8.6. For atoms with proton numbers 1 to 20, the first shell can accommodate up to two electrons, the second shell can accommodate up to eight electrons, and the third shell can accommodate up to eight electrons. Figure 8.6 The electron arrangement of sulphur atom First shell: 2 electrons Second shell: 8 electrons Third shell: 18 electrons Nucleus Figure 8.5 The electron arrangement around the nucleus Example: 21st Century Skills 21st Century Skills 172
Formation of Positive and Negative Ions You learned about the formation of positive and negative ions in Form 3. Most of the atoms have unstable electron arrangement. Therefore, these atoms will tend to form a stable electron arrangement. Neutral atoms form ions by donating the outermost electrons to other atoms or by accepting the outermost electrons of the other atoms. This is to achieve a stable duplet or octet electron arrangement. When an atom donates or accepts an electron, the atom becomes a charged particle called an ion. • Positive ions are formed when the atoms of metal elements donate electrons. • Negative ions are formed when the atoms of non-metallic elements accept electrons. As an example, a magnesium atom has 12 electrons. Its electron arrangement is 2.8.2. How does this atom achieve a stable octet electron arrangement? Would it be easier for the atom to donate two electrons or accept six electrons? Let us study Figure 8.7. Figure 8.7 Formation of positive ion, Mg 2+ Mg Magnesium atom (2.8.2) Mg 2+ Magnesium ion (2.8) Donates two electrons 8.2.3 8.2.4 Aim: To draw the electron arrangement of the first 20 elements in the Modern Periodic Table of Elements. Materials: Marker pen, A4 paper Instructions: 1. Carry out this activity in groups. 2. Determine the proton number of five different elements and relate it with the number of electrons. 3. Draw the electron arrangement for each element on a piece of A4 paper and paste it at the back of the classroom. ... ... Activity 8.4 Gallery Walk 21st Century Skills Science Science Gallery Duplet electron arrangement is the stable electron arrangement with 2 electrons in the first shell. He Duplet electron arrangement Octet electron arrangement is the stable electron arrangement with 8 electrons in the outermost shell. Ne Octet electron arrangement Elements and Substances Chapter 8 173
Formative Practice Formative Practice 8.2 1. State the position of the following elements in the Modern Periodic Table of Elements. (a) Lithium (b) Silver (c) Helium (d) Gold 2. Give two examples of elements in Group 17. 3. Element M has a proton number of 19. Based on the Modern Periodic Table of Elements, state the name of element M. 4. Element N is located in Group 15 and Period 3 in the Modern Periodic Table of Elements. What is the electron arrangement for the atom of element N? 5. Using suitable examples, state the formation of positive and negative ions from the atoms of their element. Title: Controlling Metal Corrosion Related topic: Metal corrosion occurs when the metal atoms form positive ions. Suggested duration: 1 week Problem: One of the main problems faced by vehicles and bridges is rust. Therefore, the maintenance of bridges and vehicles is a challenge to a country’s economy. The surface of an atomic substance (for example iron) must be kept in good condition. Based on the problem above, discuss how maintenance work can be carried out on bridges and vehicles. Sources: • Science textbook (content related to the formation of ion, rusting) • Websites • Other reference materials such as scientific magazines related to ion formation and rusting Explain the appropriate methods or ways to control metal corrosion. Presentations can be in the form of multimedia presentation. Problem-based Learning ... ... Activity 8.5 8.2.4 8.2.5 The atom will tend to achieve stable electron arrangement by donating or accepting electrons from other atoms. Carry out Activity 8.5 to show the effect on a substance when ions are formed. A chlorine atom has 17 electrons. Figure 8.8 shows the chlorine atom with an electron arrangement of 2.8.7. This atom accepts one electron to achieve a stable octet electron arrangement. Figure 8.8 Formation of negative ion, Cl– Accepts one electron Cl Chlorine atom (2.8.7) – Cl Chloride ion (2.8.8) 21st Century Skills 174
8.3 Isotope All atoms of an element have the same number of protons and neutrons. However, some elements have atoms with the same number of protons but different number of neutrons. These atoms are known as isotopes. Table 8.1 shows some examples of isotopes. Table 8.1 Examples of isotopes Isotope Number of protons Number of electrons Number of neutrons Hydrogen-1 1 1 0 Hydrogen-2 1 1 1 Hydrogen-3 1 1 2 Carbon-12 6 6 6 Carbon-13 6 6 7 Carbon-14 6 6 8 Oxygen-16 8 8 8 Oxygen-18 8 8 10 Isotopes are usually written only by their nucleon number. The nucleon number is the total number of protons and neutrons in the nucleus of that atom. For example, the isotope for hydrogen has 1 proton and 2 neutrons, written as hydrogen-3. Carry out Activity 8.6 to determine the number of protons, neutrons and nucleon number in other isotopes. Aim: To determine the number of protons, neutrons and the nucleon number of isotopes. Instructions: Complete the table below with the number of protons, neutrons and the nucleon number for the given isotopes. Isotope Number of protons Number of neutrons Nucleon number Chlorine-35 18 Chlorine-37 37 Sodium-23 11 Sodium-24 13 Bromine-79 79 Bromine-81 35 Activity 8.6 The word isotope originates from the Greek word ‘isos’ which means same and ‘topos’ means place. This word means isotope for an element that has the same position in the Modern Periodic Table of Elements. Isotopes http://bukutekskssm. my/Science/F4/ VIDEO Isotope.mp4 8.3.1 8.3.2 8.3.1 8.3.2 History Corner Elements and Substances Chapter 8 175
Food technology Gamma radiation from cobalt-60 is used to kill cancer cells. Photograph 8.3 Radiotherapy machine Medical The Use of Isotopes in Various Fields Technological advances have led to the widespread use of isotopes. Without realising, isotopes in the form of radioisotopes are actually widely used around us. Radioisotopes are unstable isotopes that emit radioactive radiation. Even though radioisotopes emit harmful radiation, it has important uses if handled correctly. Radioisotopes are used in medical field, agriculture, industry, power generation and research. Recall the use of radioactive radiation that you learned in Form 3 as shown below. Gamma radiation from cobalt-60 is also used to destroy the microorganism on vegetables without changing the quality of the food. Photograph 8.4 Vegetables that are free of germs Phosphorus-32 is injected into the root of plants to study the rate of absorption of phosphorus fertiliser in plants. Photograph 8.5 Plant roots Agriculture 8.3.3 176
Do you know the use of other isotopes? Let us carry out Activity 8.7. 8.3.3 Formative Practice Formative Practice 8.3 1. State the definition of isotopes. 2. Give three examples of isotopes. 3. An atom has 10 protons, 10 neutrons and 10 electrons. What is the nucleon number of that atom? 4. What are the uses of isotopes in the medical field? Aim: To search information on the use of the isotopes in various fields. Instructions: 1. Carry out this activity in pairs. 2. Search for information from various sources on the use of isotopes in various fields for 20 minutes. 3. Share and discuss the results obtained with a partner. 4. Present the information obtained in the table as follows. Field Isotope Uses Medical Sodium-24 Cobalt-60 Iodine-131 Agriculture Phosphorus-32 Carbon-14 Archaeology and Geology Carbon-14 Food technology Cobalt-60 Paper industry Americium-241 Electricity generation Uranium-235 ... ... Activity 8.7 Think-Pair-Share 8.3.3 21st Century Skills Elements and Substances Chapter 8 177
Types of particles Groups and Periods Electron arrangement Matter Definition of isotopes Uses of isotopes Isotopes Atomforms forms forms Atomic substances Molecule Molecular substances Ion Ionic substances Positive ions MedicalAgriculture IndustryPower generationResearch Negative ions ELEMENTS AND SUBSTANCES Modern Periodic Table of Elements Formation of ions 178
1. Photograph 1 shows two types of substances. Photograph 1 (a) State the type of particles that form: (i) salt (ii) sugar (b) Give two other examples of substances that are formed from the same type of particles as salt and sugar. (c) Give two examples of substances that contain the oxygen that exists in the form of molecules and ions. Summative Practice Summative Practice 8 After studying this chapter, you are able to: 8.1 Matter Explain the atomic substances, molecular substances and ionic substances with examples. Explain the existence of elements in various forms. 8.2 Modern Periodic Table of Elements Analyse the Modern Periodic Table of Elements. Deduce the principle of the arrangement of the elements in the Modern Periodic Table of Elements. Draw and write the electron arrangement of elements in its group. Explain the formation of positive ions and negative ions. Justify the loss and gain of electrons to achieve the stable electron arrangement. 8.3 Isotope Explain isotopes with examples. Determine the number of proton, number of neutron and nucleon number in isotopes. Communicate the use of isotopes in various fields. Self-reflection Self-reflection Objective Questions http://bukutekskssm. my/Science/F4/Q8 QUIZ Elements and Substances Chapter 8 179
2. Figure 1 shows part of the Modern Periodic Table of Elements. P Q R T U S Figure 1 P, Q, R, S, T and U are the letters used to represent the elements in the Modern Periodic Table of Elements which is not the correct symbol of that element. (a) How are these elements arranged in the Modern Periodic Table of Elements? (b) Which elements belong to the same group? (c) Which element exists as a stable atom? Explain your answer. (d) An element has a nucleon number of 32 and a proton number of 16. Where is the element located in the Modern Periodic Table of Elements? (e) State the electron arrangement of the following elements: (i) P (ii) Q (iii) T 3. Table 1 shows several elements with their proton numbers and nucleon numbers respectively. Table 1 Element Proton number Nucleon number X 13 27 Y 17 35 Z 20 40 (a) Determine the number of neutrons for the atomic elements X, Y and Z. (b) Draw the electron arrangement for the atomic element X, Y and Z. (c) In your opinion, where are the elements X, Y and Z located in the Modern Periodic Table of Elements? (d) How do atoms of the following elements achieve a stable electron arrangement? (i) Element X (ii) Element Y 180
4. Table 2 shows the elements P, Q, R and S with their respective proton and nucleon numbers. Table 2 Element Proton number Nucleon number P 15 32 Q 11 24 R 11 23 S 6 14 (a) Which element is a pair of isotope? Explain your answer. (b) State the uses of the isotopes you mentioned in question 4(a) in medicine and in the field of industry. (c) State element P and its uses in agriculture. (d) Name element S and state its uses in agriculture and archaeology. Mind Challenge Challenge 5. Akmal received a complaint about the cracked road condition even after repairing it many times. It was found that the soil beneath the road suddenly became soft due to leakage of the underground pipeline. How did Akmal solve the problem? The problem should be solved by following the steps below: • identifying the problem • clarifying the problem • stating the steps in solving the problem Elements and Substances Chapter 8 181
Chemicals in Industry Alloy Components of glass and ceramic Natural polymer Synthetic polymer Natural rubber Vulcanised rubber Vulcanisation of rubber Keywords 9 182 Chapter
Double Glazed Windows Double glazed windows consist of two layers of glass panels combined as one with empty space in between and inserted into a window frame or a door. Double glazed windows are better than windows with one glass panel because it can reduce the flow of incoming heat and cools down the space inside a building. In addition, this window is also soundproof. Double glazed windows also increase the security of the home as two glass panels are tougher to break compared to one glass panel. For safety purposes, it is better to choose a thicker glass panel or laminated glass. Anda akan belajar tentang: alloy glass and ceramic polymer Digest Science What is an alloy? What is superconductor alloy? How are glass and ceramic made? Are there different types of glass and their specific uses? What is a polymer? What are some examples of natural polymers and synthetic polymers? You will learn about: Chemicals in Industry 183 Chapter 9
9.1 Alloy Many objects around us are made of alloys. Photograph 9.1 shows some of the objects that are made of alloys. Alloy Composition Properties Uses Steel Iron 99% Carbon 1% • Hard and strong • Construction materials for buildings and bridges • To make frame of vehicles and railway tracks Pewter Tin 96% Copper 3% Antimony 1% • Lustre • Resistant to corrosion • To make decorative items such as photo frames Bronze Copper 88% Tin 12% • Hard • Resistant to corrosion • Attractive colour • To make monuments, metal sculptures, coins, medals and others Brass Copper 75% Zinc 25% • Strong • Has shiny surface • Malleable • Gold in colour • To make keys, door knobs, musical instruments such as trumpet Duralumin Aluminium 95% Copper 3% Magnesium 1% Manganese 1% • Light • Strong • Resistant to corrosion • To make frame of aircrafts, aeroplanes and others What is an Alloy? An alloy is a mixture of several types of metals or a mixture of metal and non-metal by a certain percentage. There are several types of alloys which are commonly used in daily life such as steel, pewter, bronze, brass and duralumin. Table 9.1 shows the composition, properties and the uses of these alloys. 9.1.1 Table 9.1 Composition, properties and the uses of alloy Photograph 9.1 Objects made of alloys Interactive Game 184
Aim: To build a model of particle arrangement in pure metals and alloys. Instructions: 1. Carry out this activity in groups. 2. Choose one type of alloy which is different from the other groups. 3. Use recycled materials to build a model of the particle arrangement in the alloy and its pure metal. 4. Present the model in front of the class. Activity 9.1 Gallery Walk 9.1.1 Why is an alloy produced? Generally, most pure metals are soft and can corrode easily. These properties are not suitable for producing most of the things around us. Therefore, the process of forming alloys or alloying is done to improve the properties of pure metal. The atoms in a pure metal are arranged orderly in layers. The layers of atoms in pure metal slide over each other easily when force is applied. Force The layers of atoms slide over easily Figure 9.1 Arrangement of atoms in a pure metal When one or more metal or non-metal elements are added into pure metal, the atoms from these elements make the layers of pure metal atoms difficult to slide over each other. This is because foreign atoms have different sizes. This makes alloys stronger and harder than pure metals. Atoms of pure metal Atoms of foreign element + Alloy Atom of pure metal Atom of foreign element When force is applied, the layers of atoms in pure metal have difficulty to slide over each other Figure 9.2 An alloy The composition or percentage of the contents of each element in alloys can be altered based on its use. HISTORY The first alloy found was bronze. Bronze was discovered hundreds of years back, in the prehistoric age known as the Bronze Age. During this period, bronze was used to make tools and weapons. with... with... science integration integration Brain Teaser Tease Does alloy exist naturally? 21st Century Skills Chemicals in Industry 185 Chapter 9
Experiment 9.1 Several properties of alloys and pure metals can be investigated through experiments in the laboratory. Let us carry out Experiment 9.1 and Experiment 9.2. Aim: To study the hardness of alloys compared to pure metals. Problem statement: Is alloy harder than pure metal? Hypothesis: Alloy is harder than pure metal. Variables: (a) manipulated: Types of metal blocks (b) responding: Diameter of the dent (c) constant: Diameter of steel ball, height of the weight, mass of the weight Materials: Copper block, bronze block, cellophane tape, thread Apparatus: Steel ball, weight (1 kg), retort stand and clamps, ruler, metre rule Procedure: 1. Prepare the apparatus as shown in Figure 9.3. Thread Copper block Cellophane tape Retort stand Steel ball Weight (1 kg) Metre rule Figure 9.3 Setup of apparatus 2. Hang a 1 kg weight 50 cm above the copper block. 3. Release the weight so that it falls onto the steel ball attached to the copper block. 4. Observe and measure the diameter of the dent formed on the surface of the copper block using a ruler. 5. Repeat steps 2 to 4 twice on different surfaces to obtain an average diameter of the dents on the copper block. 6. Repeat steps 2 to 5 by replacing the copper block with the bronze block. Result: Metal block Diameter of the dent (cm) Average diameter 1 2 3 (cm) Copper Bronze Conclusion: Is the hypothesis of this experiment accepted? What is the conclusion of this experiment? Questions: 1. Which is harder, the copper block or the bronze block? 2. Draw the arrangement of atoms in both blocks. 3. Why is the diameter of the dent for both blocks different? 9.1.2 186
9.1.2 Besides the hardness and resistance to corrosion, what are the other properties of an alloy that distinguish it from pure metal? Discuss your answers with your teacher and friends. Experiment 9.2 Aim: To study the resistance to corrosion of alloys as compared to pure metals. Problem statement: Is alloy more resistant to corrosion compared to pure metal? Hypothesis: Alloy is more resistant to corrosion than pure metal. Variables: (a) manipulated: Types of nails (b) responding: The presence of brown layer on the nail (c) constant: Size of nails, type of solution, duration of experiment Materials: Iron nail, steel nail, water Apparatus: Test tubes, test tube rack Procedure: 1. Label the test tubes as P and Q. 2. Fill test tubes P and Q with 10 ml of water. 3. Put the iron nail into test tube P and the steel nail into test tube Q. Test tubes Water P Q Iron nail Steel nail Figure 9.4 Setup of apparatus 4. Place both test tubes in a test tube rack on the laboratory table and leave them for a week. 5. After a week, record your observations. Result: Type of nail The presence of brown layer on the nail Iron nail Steel nail Conclusion: Is the hypothesis of this experiment accepted? What is the conclusion of this experiment? Questions: 1. Which nail will rust after a week? 2. Draw the arrangement of atoms in both nails. 3. Why is the resistance to corrosion for both nails different? Precautionary measures: Ensure that both nails are rub using sandpaper before conducting the experiment, in order to clean the surface of the nails. Chemicals in Industry 187 Chapter 9
9.1.3 The Use of Alloys in Daily Life Alloys have specific uses based on their unique properties. Steel is used for constructing skyscrapers because of its hardness and resistance to corrosion. The body of an aeroplane is made of light and strong duralumin. Some musical instrument are made of brass which is shiny and resistant to corrosion. Several types of metal elements and non-metal elements have superconducting properties at low temperature and are added to make superconductor alloys. Superconductors are materials that can conduct electricity at high efficiency without resistance. A superconductor is also able to resist a magnetic field causing the superconducting material to float when placed on a magnet. Photograph 9.6 Magnetic Resonance Imaging (MRI) machine Photograph 9.2 Petronas Twin Tower Photograph 9.3 Aeroplane Photograph 9.4 Saxophone Superconductor alloys are used for the construction of the railway track of a high-powered train to make sure the train moves by floating and to prevent friction between the track and the body of the train. This allows the train to move at high speed. Photograph 9.5 Maglev train Superconductor alloys such as niobium-titanium and niobium-tin are used in the construction of the Magnetic Resonance Imaging (MRI) machine for medical imaging. 188
9.2.1 Formative Practice Formative Practice 9.1 1. Give two examples of alloy containing copper metal. 2. Draw the arrangement of atoms in an alloy and a pure metal, then relate the arrangement of the atoms to the properties of pure metal. 3. What alloy is used to make the body of an aeroplane? Explain why the alloy is chosen. 9.2 Glass and Ceramic What is Glass? Glass is believed to have been used since 5000 B.C. Glass is made of silica. Silica is a compound that contains silicon dioxide and exists naturally in sand. Pure silica melts and liquefies at around 1500°C to form glass. Photograph 9.7 Silica Photograph 9.8 Glass bottle Several types of glass are made in the glass industry. Table 9.2 shows the types of glass with their composition and properties. Table 9.2 Types of glass with their composition and properties Glass Composition Properties Fused silica glass • Silica • Resistant to heat • Chemically inert Soda-lime glass • Silica • Calcium carbonate • Sodium carbonate • Low melting point • Easy to shape Borosilicate glass • Silica • Boron oxide • Sodium oxide • Aluminium oxide • High resistance to heat and chemicals compared to soda-lime glass Lead crystal glass • Silica • Lead(II) oxide • Sodium oxide • Low melting point • High refractive index Chemicals in Industry 189 Chapter 9