Focus On Science Workbook Grade 8

5.4 Mixtures 1. (a) What is a mixture? A mixture has two or more components that are physically combined. (b) Give three examples of mixtures. Seawater, soil and blood (c) Zaki adds some red beans to some uncooked rice in a bowl. Then, he mixes them with a spoon. (i) Is the product a mixture? Yes (ii) Can Zaki separate the components from the product formed? How can he do it? Yes, he can separate them by using his hand or a sieve. 2. We can categorise mixtures based on their appearance. They are homogeneous and heterogeneous mixtures. (a) Give two examples of each type of mixture. Homogeneous mixtures: Coffee, air Heterogeneous mixtures: Soil, pizzas (b) When sugar is mixed with water, the mixture formed is an example of a homogeneous mixture. Explain why. The composition is uniform because we cannot see the sugar in the mixture. We cannot separate them easily. (c) When sand is added to water and mixed, the mixture formed is an example of a heterogeneous mixture. Explain why. The composition is not uniform because we can see the sand in the mixture. We can separate the sand from the mixture through filtration. (d) Give one general difference between a homogeneous mixture and a heterogeneous mixture. A homogeneous mixture has a uniform composition while a heterogeneous mixture has a non-uniform composition.//A homogeneous mixture consists of one phase of matter while a heterogeneous mixture consists of two or more phases. 98 ©Praxis Publishing_Focus On Science

3. State if the mixtures are homogeneous or heterogeneous. (a) A vanilla ice cream Homogeneous mixture (b) A bowl of fruits Heterogeneous mixture (c) A burger Heterogeneous mixture 4. There is another way to categorise mixtures based on their particle sizes. Fill in the table by stating the types of mixtures and their relative particle sizes. Type of mixture Solution Colloid Suspension Relative particle size Very small Medium Large 5. A tablespoonful of sugar is added to a glass of water and stirred. Sugar water, a type of mixture is formed. Sugar Water Sugar water (a) (i) Is the sugar water a solution, colloid or suspension? Solution (ii) Explain your answer. The sugar water appears uniform throughout and no particles settle at the bottom of the beaker after the solution is stirred. (b) Which is the solute? Which is the solvent? The sugar is the solute. The water is the solvent. (c) Give two other examples of this type of mixture. Air, salt water Chapter 5 Elements, Compounds and Mixtures 99 ©Praxis Publishing_Focus On Science

6. A tablespoonful of soil is added to a glass of water and stirred. The mixture is left for 10 minutes. (a) (i) What happens to the mixture after 10 minutes? The soil settles at the bottom of the beaker. (ii) Explain your answer. The soil particles are very large. They settle down at the bottom of the beaker because gravity pulls them down. (b) Name the type of mixture formed. Suspension (c) Give two other examples of this type of mixture. Paint, flour in water 7. Fog is an example of colloid which is a type of mixture. (a) What is fog considered a mixture? Fog is the tiny water droplets suspended in the air. (b) What is a colloid? A colloid is a type of mixture that appears clear when it is diluted, but cloudy when it is concentrated. (c) How does a colloid differ from a suspension? The particles of a colloid do not settle down after some time but the particles of a suspension do. (d) Give two other examples of colloids. Milk, mayonnaise 8. Tick (✓) the correct general properties of mixtures. (a) Mixtures are formed by chemical reactions. (b) All components of a mixture retain their original physical properties. ✓ (c) The components in a mixture have a fixed ratio. (d) A mixture can be separated by a physical process. ✓ 100 ©Praxis Publishing_Focus On Science

9. Fill in the chart to compare and contrast between mixtures and compounds. Mixtures Compounds Similarity Both have two or more different components. Differences Any formation of new substances? Any fixed composition? Any chemical bonds between components? Any fixed boiling and melting points? No No No No Yes Yes Yes Yes 10.A student uses the apparatus set-up below to separate water from a salt solution. Thermometer Beaker Distillation flask Water out Liebig condenser Water in Salt solution Bunsen burner (a) What happens when the salt solution is heated? The water in it turns into water vapour and escapes from the solution. (b) What happens in the Liebig condenser? The water vapour is cooled when it touches the cold surface and condenses into water. (c) What is collected in the beaker? Water (d) What happens if the heating continues? The salt solution becomes concentrated. In the end, salt residues are left. Extra Info Distillation i Chapter 5 Elements, Compounds and Mixtures 101 ©Praxis Publishing_Focus On Science

11. Four dye solutions are labelled P, Q, R and S. The figure below shows a chromatogram obtained from the four solutions and three other solutions containing a single dye (red, green and blue). P Q R S Red dye Green dye Blue dye (a) Name the method used to separate the various dyes in a given coloured solution shown in the figure. Paper chromatography (b) Which of the four solutions, P, Q, R or S contain (i) one known dye only: Solution Q (ii) two known dyes only: Solution P (iii) three known dyes only: Solution S (iv) red and green dyes: Solution S (v) an unknown dye: Solution R 12. The list below shows various methods for separating mixtures. Evaporation Centrifugation Fractional distillation Sublimation Paper chromatography Filtration Select one technique from the list above that can be used to separate each of the mixtures below. (a) The black pigment component in a dye: Paper chromatography (b) Alcohol and water: Fractional distillation (c) Mud from mud water: Evaporation (d) Dust from the air using a face mask: Filtration (e) Dry ice from its impurities: Sublimation (f) Water from wet clothes in washing machines: Centrifugation 102 ©Praxis Publishing_Focus On Science

1. Which of the following are contained in the nucleus of an atom? I Protons III Electrons II Neutrons A I and II only C II and III only B I and III only D I, II and III 2. Which is correct about molecules? A A molecule can be made up of different elements. B Molecules have more than one type of element. C O2 and N2 are examples of molecules of compounds. D A molecule can have the maximum number of 8 atoms only. 3. The figure shows substance M. Which of the following is most probably substance M? A Carbon dioxide C Ammonia B Oxygen D Zinc 4. Which is an element? A Oxygen C Water B Salt D Carbon dioxide 5. Which of the following statements is not correct about elements? A Copper is an element because it contains only copper atoms. B All known elements are listed in the Periodic Table of Elements. C Elements can be atoms or molecules. D Elements are in the forms of solid and liquid only. Objective Questions A B C D Choose the best answer. 6. Which of the following is not matched correctly? Element Symbol A Carbon C B Sodium S C Oxygen O D Potassium K Read the text below and answer questions 7 and 8. The Periodic Table is a table that shows the listing of elements. Elements are listed in the table in the order of the number of protons in each atom. It gives information about the elements such as the number of protons and electrons they have. This table makes studying elements easier. 7. There were about 100 elements in the Periodic Table in the 1960s. However, now there are 118 elements. How is this possible? A More elements have been discovered. B Scientists have broadened the definition of elements. C Some elements were found on the Moon later. D Some elements disintegrated into new elements. Chapter 5 Elements, Compounds and Mixtures 103 ©Praxis Publishing_Focus On Science

8. Imagine that the Periodic Table of Elements was not created. Which is most likely to happen? A We would have fewer elements. B Scientists cannot predict the properties of the elements and their compounds easily. C The elements might be arranged in alphabetical order. D There might be more reactions between the elements. 9. Why are metalloids useful as semiconductors? A They can conduct electricity better under certain conditions. B They are located between the metals and non-metals in the Periodic Table. C They can change their physical forms easily. D They are brittle. 10. Which of the following are compounds? W X Y Z A W and Z only B X and Y only C W, X and Y only D W, X, Y and Z 11.What are the differences between gold and carbon? I Gold is shiny while carbon is dull. II Carbon can conduct heat but gold is a bad conductor of heat. III The melting point of gold is low but the melting point of carbon is high. IV Gold can be beaten into a flat piece but carbon breaks up. A I dan II only B I dan IV only C II dan III only D III dan IV only 12.Which statements are correct about solutions? I Solutions are homogeneous mixtures. II Solutions appear uniform throughout. III Salad dressing and sugar water are examples of solutions. A I and II only B I and III only C II and III only D I, II and III 13.Water and alcohol can be separated by fractional distillation because they A have different densities B have different boiling points C have different colours D are immiscible liquids 14. The figure below shows a separation method used on a salt solution. Wire gauze Bunsen burner Tripod stand Evaporating dish Salt solution Which of the following observations proves that the salt solution is a mixture? A It boiled after a while. B There were bubbles in the solution. C White crystals were left in the evaporating dish after some time. D It did not burn. 104 ©Praxis Publishing_Focus On Science

Complete the concept map below about elements, compounds and mixtures. Concept Map Compounds Mixtures Symbols Periodic Table of Elements Solutions Differences Homogeneous mixtures Heterogeneous mixtures Chemical formulas Suspensions Colloids Filtration Evaporation Sublimation Distillation Chromatography Centrifugation Molecules Molecules of a compound Molecules of an element Metals Non-metals Metalloids Electrons Protons Neutrons Atoms Elements subatomic particles combined chemically to form make up types types based on composition combined physically to form different types of atoms make types based on particle size separation methods Chapter 5 Elements, Compounds and Mixtures 105 ©Praxis Publishing_Focus On Science

HOTS Daily Application Yassin and his classmates went camping by a river for a few days. They did not bring enough drinking water. They decided to boil the river water, but the water contained a lot of impurities such as twigs, leaves, sand and soil. Suggest a way how they can separate the impurities from the river water with the limited things they have. Explain briefly and sketch your method. They can filter the water. Firstly, cut a water bottle into two parts. Turn the top part upside down. Fill it with a cloth and then with some sand and pebbles. Then, pour the river water into it and collect the water that comes out at the bottom. The filtered water is clearer free from larger debris. Raw water Pebbles Cloth Fine sand Filtered water Online Quick Quiz 106 ©Praxis Publishing_Focus On Science

Acids and Alkalis CHAPTER 6 6.1 Acids and Alkalis 1. Write ‘acidic substance’, ‘neutral substance’ or ‘alkaline substance’. (a) Toothpaste Alkaline substance (b) Tea Acidic substance (c) Orange juice Acidic substance (d) Cooking oil Cooking oil Neutral substance (e) Carbonated drink Acidic substance (f) Drain cleaner Alkaline substance (g) Bleach Bleach Alkaline substance (h) Rainwater Acidic substance Chapter 6 Acids and Alkalis 107 ©Praxis Publishing_Focus On Science

2. The table below shows several activities carried out to find the properties of acids. Fill in the inference column on the properties of acids. Activities Observation Inference (a) Ayu tastes some lemon juice. The juice is sour. Acids taste sour. (b) Ayu dips the blue litmus paper into some lemon juice. Blue litmus paper The blue litmus paper turns red. Acids turn blue litmus paper red. (c) Ayu puts a drop of concentrated hydrochloric acid on a piece of filter paper. Concentrated hydrochloric acid Filter paper A hole is formed. Acids are corrosive. (d) Ayu connects some lemons with some wires, a bulb, copper rods and zinc nails as shown below. Zinc nail Zinc nails Bulb Copper rods The bulb lights up. Acids conduct electricity. (e) Ayu places a magnesium ribbon into a test tube filled with hydrochloric acid. Then, she covers the mouth of the test tube for 5 minutes. Finally, she tests the gas produced with a lighted wooden splinter. Gas collected Dilute hydrochloric acid Magnesium ribbon Lighted splinter A lot of bubbles are released. The collected gas gives out a pop sound when tested with the lighted wooden splinter. Acids react with magnesium to release hydrogen gas. 108 ©Praxis Publishing_Focus On Science

3. Liquid Y has a sour taste. When a blue litmus paper is dipped into liquid Y, the litmus paper turns red. Is liquid Y an acid or an alkaline? Describe a chemical test to confirm it. Liquid Y is an acid. An acid reacts with a metal to produce hydrogen gas. Add a magnesium strip into liquid Y. Hydrogen gas will be released which will give a pop sound when tested with a lighted wooden splinter. 4. We can find hazard warning symbols on bottles of chemicals in our laboratories. (a) Why are hazard warning symbols found on bottles of chemicals? They warn us of the dangers of handling the contents. (b) Why are symbols used instead of words? Symbols make people understand faster and are useful especially in scenarios where a quick response is needed. (c) (i) What does the hazard warning symbol shown here mean? The contents of the bottle is corrosive. It can cause damage to the skin or eyes upon contact. (ii) What bottles of chemicals usually have this hazard warning symbol? Bottles containing acids (iii) What should you do immediately if the content of a bottle bearing this symbol spills on your hand? Rinse my hand quickly under a lot of running water. 5. List three things around us that are alkaline. Soap, toothpaste, baking soda 6. Hana sets up the apparatus as shown. (a) Predict if the bulb will light up when the switch is turned on. Yes, it will light up. (b) Give your reason. Sodium hydroxide solution is an alkaline solution. Alkaline solutions conduct electricity. Battery Bulb Switch Carbon electrodes Sodium hydroxide solution Extra Info Alkalis conduct electricity i Chapter 6 Acids and Alkalis 109 ©Praxis Publishing_Focus On Science

7. Complete the chart below on the properties of alkalis. Feel slippery and soapy Good electrical conductors Corrosive Properties of alkalis React with acids to produce salt and water Change red litmus paper blue Taste bitter 8. Complete the chart below to compare and contrast acids and alkalis. Similarities • Both are corrosive. • Both are good conductors of electricity. • Both change the colour of litmus paper. Feel when touched Differences Taste Effect on red litmus paper Effect on blue litmus paper Reaction with metals Sour Not slippery No effect Turn red React with metals to release hydrogen gas Bitter Slippery Turn blue No effect No reaction with most metals Acids Alkalis 110 ©Praxis Publishing_Focus On Science

9. Zaki put a piece of dry blue litmus paper into a test tube filled with solid citric acid as shown. (a) (i) Did the dry blue litmus paper change its colour? If yes, what colour did it change into? No. (ii) Explain your answer. There was no water. Acids need water to show its properties. (b) Zaki then added some water into the test tube. (i) Did the dry blue litmus paper change its colour? If yes, what colour did it change into? Yes. It changed to red. (ii) Explain your answer. Acids show its properties in the presence of water. (c) Zaki repeated the activity by replacing solid citric acid with solid barium hydroxide and dry blue litmus paper with dry red litmus paper. (i) Did the dry red litmus paper change its colour? If yes, what colour did it change into? No. (ii) Explain your answer. There was no water. Alkalis need water to show its properties. 10. The figure below shows the results of an experiment carried out to study the properties of acids and alkalis. Blue litmus paper Turns red Substance X Remains red Red litmus paper Blue litmus paper Remains blue Substance Y Turns blue Red litmus paper (a) Conclude substances X and Y. Substance X is an acid. Substance Y is an alkali. Dry blue litmus paper Solid citric acid Chapter 6 Acids and Alkalis 111 ©Praxis Publishing_Focus On Science

(b) Give an example that is most probably substances X and Y, respectively. Substance X: Vinegar (or other acidic substances) Substance Y: Milk of magnesia (or other alkaline substances) 11. Categorise these substances into acidic, neutral and alkaline. Acidic Vinegar Orange juice Shampoo Coffee Neutral Distilled water Salt water Sugar water Alkaline Laundry detergent Soap Milk of magnesia Blood Vinegar Laundry detergent Distilled water Soap Orange juice Salt water Shampoo Milk of magnesia Coffee Blood Sugar water 12.We use litmus papers to determine if a substance is alkaline or acidic. Name two other methods of testing instead of using litmus papers. Use pH indicators or use a pH meter 13. Complete the table below with the colours of pH indicators when they are in acidic, neutral and alkaline solutions. pH indicator Colour in an acidic solution Colour in a neutral solution Colour in an alkaline solution Phenolphthalein Colourless Colourless Pink Methyl orange Red Yellow Yellow Litmus solution Red Purple Blue Universal indicator Red Green Purple Bromocresol green Yellow Blue Blue 112 ©Praxis Publishing_Focus On Science

14. Minah is making a pH indicator at home. She blends some red cabbage with some water in a blender and then she strains the juice from the cabbage. (a) What is the colour of the red cabbage juice? Purple (b) Minah pours some red cabbage juice into some lemon juice. What colour does the cabbage juice change into? Pink (c) Minah pours some red cabbage juice into an unknown solution. She notices that the juice turns blue. What inference can you say about the solution? The solution is alkaline. (d) Suggest a way to make some noodles that have both purple and pink colours. Soak the noodles in the red cabbage juice for a while and the noodles will turn purple. Then, add some lemon juice to some parts of the noodles. These parts of the noodles will turn pink. (e) Besides red cabbage, suggest another plant that we can use as a pH indicator. Turmeric 15. (a) What is the pH scale? A set of numbers to indicate if a solution is acidic, neutral or alkaline. (b) Draw the pH scale in the space below. Indicate the range of pH that shows acidic, neutral and alkaline. Acidic Neutral Alkaline 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 (c) What does a neutral solution mean? It is neither acidic nor alkaline. (d) What is the advantage of using the universal indicator compared to litmus paper? The universal indicator can show the pH value of a substance. Litmus paper can only determine if a solution is acidic or alkaline. Extra Info Coloured noodles i Chapter 6 Acids and Alkalis 113 ©Praxis Publishing_Focus On Science

16. The table below shows the pH of a few solutions. Solution W X Y Z pH 13 3 9 7 (a) Tick (√) the boxes given to indicate solutions W, X, Y and Z. (i) W: (ii) X: Laundry detergent ✓ Vinegar Vinegar ✓ Baking soda (iii) Y: (iv) Z: Distilled water Baking soda ✓ Laundry detergent Distilled water ✓ (b) Among the four solutions, which is the strongest acid and which is the strongest alkali? Strongest acid: Solution X Strongest alkali: Solution W (c) (i) State two pairs of solutions that will react to produce a salt and water. Solutions X and W, solutions X and Y (ii) Give a reason for your answer. An acid and an alkali react to produce a salt and water. 17. The underlined words are incorrect. Replace them with the correct words. (a) Alkalis are sweet and feel soapy. bitter (b) Acids react with most metals to give out carbon dioxide gas. hydrogen (c) Oranges and lemons are acidic as they contain tartaric acid. citric (d) An alkali only shows its alkaline properties in the presence of air. water (e) The pH scale ranges from 0 to 12. 14 (f) Alkalis have pH values less than 6. more, 7 (g) The pH value of a solution can be determined by using phenolphthalein. universal indicator (h) A stronger acid has a greater pH value. smaller 114 ©Praxis Publishing_Focus On Science

18. The figure below shows the colour of universal indicator in solutions of different pH values. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Red Orange Yellow Green Dark green Blue Purple (a) (i) An oven cleaner has a pH value of 13. What is the colour of universal indicator in the oven cleaner? Purple (ii) Suggest a substance in the oven cleaner that gives a pH value of 13. Sodium hydroxide (b) Universal indicator turns yellow in some grape juice. (i) What is the pH value of the grape juice? 5 to 6 (ii) Suggest a substance in the grape juice that gives that pH value. Tartaric acid (c) A food sample was tested with universal indicator which turned green. (i) What was the pH value of the food? pH 7 (ii) The food sample was left on the table for five days and was retested with universal indicator which turned orange. What happened? The food has spoiled. The bacteria in the food acted on it and produced an acid that lowered the pH value of the food. 19. Match to show the uses of some acids and alkalis. Sulphuric acid Ammonia Magnesium hydroxide Formic acid Vinegar To coagulate latex before being processed into latex sheets To make antacids Used in car batteries To preserve pickles To make plant fertilisers Chapter 6 Acids and Alkalis 115 ©Praxis Publishing_Focus On Science

20. Milk is an excellent source of calcium and other essential minerals. It is rich in protein for proper growth and development. However, milk has one serious shortcoming. It gets spoiled very quickly. (a) Besides having a sour taste, how do we know if the milk is spoiled? The milk has an unpleasant odour. It may change colour and have a lumpy texture. (b) Name the type of bacteria in milk that causes it to turn sour. Lactobacillus (c) Why does milk turn sour? The bacteria (Lactobacillus) converts lactose in the milk to lactic acid that makes the milk sour. (d) Briefly describe two factors that speed up the rate of milk turning sour. Temperature – The higher the temperature is, the faster the milk turns sour. Cleanliness of the container – A dirty container may contain bacteria and water which can increase the rate at which the milk turns sour. (e) Suggest a way to keep milk fresh for a longer time. Keep it at a lower temperature or in a refrigerator 21. The figure shows a forest ruined by acid rain. Extra Info Acid rain i 116 ©Praxis Publishing_Focus On Science

(a) How is acid rain formed? Sulphur dioxide and nitrogen dioxide in the air dissolve in the rain to form sulphuric acid and nitric acid. (b) How are forests ruined by acid rain? Acid rain seeps into the ground and dissolves nutrients needed by trees, such as magnesium and calcium. Thus, trees do not get enough nutrients. (c) What else are affected by acid rain besides forests? Buildings, aquatic organisms, humans 6.2 Neutralisation 1. Underline the correct words. (a) A reaction between an acid and an alkali is known as (neutralisation, decomposition). (b) An acid reacts with an alkali to produce (sugar, salt) and water. (c) When an acid neutralises an alkali, the products have a pH value of (9, 7). (d) (Dilution, Titration) is the method used to determine the volume of an acid needed to neutralise a certain volume of alkali. (e) A pH (solution, indicator) is used to show the change in pH during the neutralisation reaction. 2. Johan prepared an apparatus set-up as shown below to study the neutralisation reaction between sodium hydroxide solution and hydrochloric acid. White tile 25 cm3 of sodium hydroxide solution + phenolphthalein Hydrochloric acid Burette (a) Name the method used by Johan. Titration Chapter 6 Acids and Alkalis 117 ©Praxis Publishing_Focus On Science

(b) What is the purpose of the white tile? So that changes in the colour of the solution in the conical flask can be observed better (c) (i) What is the use of phenolphthalein? It is a pH indicator to determine the end point of titration when all the sodium hydroxide solution is neutralised by the acid. (ii) What was the initial colour of phenolphthalein in sodium hydroxide solution? Pink (d) Johan slowly added hydrochloric acid into the sodium hydroxide solution while swirling the conical flask. He stopped when the solution in the conical flask changed from pink to colourless. (i) Why must Johan add the acid slowly into the alkali? So that the end-point at which phenolphthalein changes colour can be found accurately (ii) What happened in the conical flask at the moment the colour of its solution changed? All the sodium hydroxide solution was neutralised by the acid. (iii) The table below shows the readings of the burette. Burette reading Volume (cm3) Initial reading 12.30 Final reading 37.30 How much hydrochloric acid was used to neutralise 25 cm3 of sodium hydroxide solution? 37.30 – 12.30 = 25.00 cm3 25.00 cm3 of hydrochloric acid was used. (e) Write the word equation for this reaction. Sodium hydroxide + hydrochloric acid ➝ sodium chloride + water 118 ©Praxis Publishing_Focus On Science

(f) Then, Johan poured the solution in the conical flask into an evaporating dish. He heated it until the solution dried up. Wire gauze Tripod Evaporating dish Solution (i) Describe the substance Johan found on the evaporating dish. White crystals (ii) Name the substance formed. Sodium chloride 3. Tooth decay is the damage that occurs at the surface of a tooth. If it is not treated, it can cause pain, infection and even tooth loss. It can be prevented by brushing the teeth with toothpaste. (a) How does tooth decay happen? The bacteria in our mouth act on the leftover food in between our teeth and produce acids. The acids damage the surface of our teeth, causing tooth decay. (b) Why are we advised to brush our teeth twice a day? To remove any food stuck in between our teeth (c) Why is our toothpaste alkaline? To neutralise any acids formed by bacteria on the teeth 4. A farmer found out that different plants need soil with different pH values to grow healthily. (a) Basil plants grow best in acidic soil with a pH value between 5 and 6. Suggest a way to make his neutral soil suitable for planting basil plants. He can add compost and coffee grounds to the soil. (b) After some time, he decided to grow asparagus plants which grow well in neutral soil. How should he neutralise his acidic soil? He can add quick lime or slaked lime to the soil. Chapter 6 Acids and Alkalis 119 ©Praxis Publishing_Focus On Science

1. Which of the following is acidic? A Bleach B Lime juice C Sodium hydroxide solution D Soap 2. The figure shows a property of substance Y. Red litmus paper turns blue Substance Y Which substance has the same property as substance Y? A Saltwater B Shower gel C Lemon juice D Vinegar 3. Which of the following substances has a pH value less than 7? A Tomato juice B Soap C Toothpaste D Distilled water 4. Which of the following is correct about the acids found in some fruits? Fruit Acid A Apples Malic acid B Grapes Citric acid C Lemons Tartaric acid D Bananas Sulphuric acid Objective Questions A B C D Choose the best answer. 5. Which of the following is true about acids and alkalis? Acids Alkalis A Do not react with metals React with metals and give off hydrogen gas B Have a pH value of more than 7 Have a pH value of less than 7 C Corrosive Not corrosive D Taste sour Taste bitter 6. Sulphuric acid reacts with substance X and releases a gas. When the gas is tested with a burning wooden splinter, a ‘pop’ sound is heard. Which of the following is substance X? A Sodium chloride solution B Calcium hydroxide C Zinc carbonate D Magnesium strip 7. A hazard warning symbol is found on a bottle containing sodium hydroxide solution. Which is the correct safety measure when using its contents? A Keep it away from fires and heat sources. B Keep it in a special lead container. C Avoid direct contact with our skin and eyes. D Use it in the fume chamber. 8. The table shows the colours of two pH indicators tested on substance K. Methyl orange Yellow Phenolphthalein Pink 120 ©Praxis Publishing_Focus On Science

Which is most probably substance K? A Toothpaste B Carbonated drink C Tap water D Tea 9. The figure shows a few drops of universal indicator being added into a test tube containing lime juice. Lime juice Universal indicator What is the change in colour of the universal indicator? A Red B Green C Blue D Colourless 10. Solution Y has a pH value of 3. Which of the following is not true about Y? A Y feels soapy when touched. B Y shows its properties when water is present. C When a metal is submerged in solution Y, bubbles are released. D Solution Y turns blue litmus paper red. 11. The table shows the pH values of four liquids P, Q, R and S. Liquid P Q R S pH value 11 3 7 6 Which of the following pairs of liquids neutralise each other? A P and Q B Q and S C R and S D P and R Read the text below and answer questions 12 and 13. People who are swimming, wading or diving in the sea can get stung by jellyfish. The stings leave many tiny stingers on the skin which continue to release poison into the skin. Hanif was stung by a jellyfish while swimming at a beach. When the affected parts were washed with soap and water, the pain increased a lot. 12.Which of the following best explains the situation? A The water diluted the poison. B His muscles contracted when the wound was in contact with soap. C The alkaline soap triggered the stingers to release more poison into the skin. D The stingers were washed away leaving the wounds open. 13.Which is most probably the best to apply on the affected parts to relieve his pain? A Toothpaste B Vinegar C Distilled water D Baking soda 14.Which is not true about acid rain? A It occurs when laboratories and factories release vinegar into the air. B Many stone structures are damaged by acid rain. C The Statue of Liberty in the USA turns green due to its reaction to acid rain. D Acid rain is more severe in a heavy industrial area. Chapter 6 Acids and Alkalis 121 ©Praxis Publishing_Focus On Science

Complete the concept map below Concept Map about alkalis and acids. Synthetic Phenolphthalein Methyl orange Litmus solution Phenol red Bromocresol green Universal indicator Natural Applications Titration pH scale Salt Water Precautions pH indicators Acid rain Milk turns sour Acidic soil • pH value • Taste and feel • Corrosiveness • Effects on blue and red litmus paper • Reaction with metals • Role of water produces issues related properties can be tested through react through types Neutralisation Alkalis Acids examples 122 ©Praxis Publishing_Focus On Science

HOTS Daily Application The figure below shows a bottle of acid stored in a laboratory. Why is the acid stored in a glass bottle instead of a metal can? Acids are corrosive. The acid will react with the metal can and corrode it. Acids do not react with glass. Online Quick Quiz Chapter 6 Acids and Alkalis 123 ©Praxis Publishing_Focus On Science

Structure of the Earth and Natural Disasters CHAPTER 7 7.1 Structure of Earth 1. What are landforms? Landforms are the natural physical features found on Earth’s surface which were formed due to various forces of nature. 2. Label the layers of the Earth based on the chemical composition. (a) Mantle (c) Crust (b) Inner core (d) Outer core 3. Tick (✓) the correct statements about the Earth’s layers. (a) Crust (i) It is very thin relative to the radius of the Earth. ✓ (ii) The continental crust is generally thicker than the oceanic crust. ✓ (iii) The main elements that make up this layer are iron and sodium. (b) Core (i) The inner core is in the liquid state and the outer core is in the solid state. (ii) It is mainly composed of iron and nickel. ✓ (iii) It makes up about 31% of the Earth’s mass. ✓ (c) Mantle (i) It is mainly solid with a density higher than the crust. ✓ (ii) At its upper layer, there are huge slabs of moving rock called the tectonic plates. ✓ (iii) Its temperature reduces when we move from its upper layer to its lower layer. Extra Info Landforms i Extra Info Earth’s layers i 124 ©Praxis Publishing_Focus On Science

4. Label the Earth’s layers based on their physical characteristics. (a) Lithosphere (c) Mesosphere (e) Inner core (d) Outer core (b) Asthenosphere 5. (a) What are geomorphic processes? They are the processes that change the Earth’s surface. (b) (i) Name the two types of geomorphic processes. Exogenic process and endogenic process (ii) Briefly explain how these two types of geomorphic processes differ. Endogenic processes are caused by forces that originate from within the Earth. Exogenic processes are caused by forces that originate from the Earth’s surface. 6. Tick (✓) the correct types of exogenic processes. Weathering ✓ Earthquakes Mass wasting ✓ Land subsidence Erosion ✓ Transportation and sedimentation ✓ 7. (a) What is weathering? Weathering is the breaking down of rocks on Earth’s surface into smaller pieces. (b) There are three types of weathering. Name them based on the figures shown below. List their primary causes. Type of weathering: Physical weathering Primary cause: Wind Type of weathering: Biological weathering Primary cause: Animals Type of weathering: Chemical weathering Primary cause: Chemicals such as acid rain Extra Info Types of weathering i Chapter 7 Structure of the Earth and Natural Disasters 125 ©Praxis Publishing_Focus On Science

8. What is deposition? Deposition is the process in which sediments or weathered rocks being transported stop moving and is deposited when the agent of erosion loses its energy. 9. (a) What is erosion? Erosion is the removal and transportation of weathered materials to other places. (b) How is weathering different from erosion? Weathering is the breaking down of rocks without involving any movement to another place. Erosion involves the movement of weathered rocks to a new location. 10. The figure below shows a river flowing from the mountains to the sea. (a) In which part of the river does weathering happen rapidly? Give your reason. The upper part of the river. The water moves rapidly crushing rocks on the riverbed and riversides into smaller pieces. (b) In which part of the river does deposition happen rapidly? Give your reason. The lower part of the river. The water moves slower as it loses energy. It cannot carry pieces of weathered rocks. They are deposited here. 11. Group these situations into the correct categories by writing the letters representing them in the box below. A – Murky water flowing down a hill during a heavy downpour B – Waves dropping sand on the beach C – Pebbles being carried away by a fast-moving river D – Layers of sediment forming at the bottom of the ocean 126 ©Praxis Publishing_Focus On Science

E – Water getting into cracks, and then freezing and breaking the rocks apart F – Flood water pounding against a canyon wall and wearing it down G – Deltas forming at river mouths H – Sand carried by wind hitting rocks and breaking them I – Wind blowing sand from one location to another Weathering Erosion Deposition E, F, H A, C, I B, D, G 7.2 Movement of Tectonic Plates 1. (a) What are tectonic plates? They are extremely large pieces of the Earth’s crust and uppermost mantle. (b) There are a few major tectonic plates covering most of the Earth’s surface. Name them based on the map below. A B G C D E F A: Pacific Plate B: North American Plate C: South American Plate D: African Plate E: Eurasian Plate F: Australian Plate G: Antarctic Plate Chapter 7 Structure of the Earth and Natural Disasters 127 ©Praxis Publishing_Focus On Science

2. Underline the correct words to explain how the tectonic plates move. Inside the Earth, it is very (cold, hot). The heat mostly comes from the (atmosphere, core) of the Earth. The hot mantle in the Earth can move (slowly, fast) due to convection. Convection is the process of warm fluid (sinking, rising) and cooler fluid (sinking, rising). This slow movement of the mantle moves the tectonic plates at the (bottom, surface). It is believed that the tectonic plates move 2 to 15 (cm, m) per year. 3. Tick (✓) the correct columns in the tables to describe the different types of tectonic boundaries. (a) Motion of plates: Towards each other Sliding past each other Away from each other ✓ An example: San Andrea Fault Mariana Trench Himalayan Mountain Range Mid-Atlantic Ridge ✓ Type of boundary: Divergent boundary ✓ Convergent boundary Transform boundary New feature(s) formed: Ridges and rifts ✓ Trench Mountain ranges Faults 128 ©Praxis Publishing_Focus On Science

(b) Motion of plates: Towards each other ✓ Sliding past each other Away from each other An example: San Andrea Fault Mariana Trench ✓ Himalayan Mountain Range Mid-Atlantic Ridge Type of boundary: Divergent boundary Convergent boundary ✓ Transform boundary New feature(s) formed: Ridges and rifts Faults Trench ✓ Mountain ranges (c) Motion of plates: Towards each other ✓ Sliding past each other Away from each other An example: San Andrea Fault Mariana Trench Himalayan Mountain Range ✓ Mid-Atlantic Ridge Type of boundary: Divergent boundary Convergent boundary ✓ Transform boundary New feature(s) formed: Ridges and rifts Faults Trench Mountain ranges ✓ Chapter 7 Structure of the Earth and Natural Disasters 129 ©Praxis Publishing_Focus On Science

(d) Motion of plates: Towards each other Sliding past each other ✓ Away from each other An example: San Andrea Fault ✓ Mariana Trench Himalayan Mountain Range Mid-Atlantic Ridge Type of boundary: Divergent boundary Convergent boundary Transform boundary ✓ New feature(s) formed: Ridges and rifts Faults ✓ Trench Mountain ranges 7.3 Earthquakes 1. Match the terms and their descriptions correctly. Aftershock The point in the Earth that is the origin of an earthquake Epicentre The record of an earthquake that is produced by a seismograph Focus A smaller earthquake that occurs after the main earthquake in the same place Seismogram The study of earthquakes Richter scale A magnitude scale to categorise the strength of earthquakes Seismology The point on the Earth’s surface directly above the focus of the earthquake Seismograph An instrument that records the surface movement caused by the seismic energy of an earthquake 130 ©Praxis Publishing_Focus On Science

2. (a) What is the Ring of Fire? It is the geographical area on the Earth that has most of the active volcanoes and is prone to earthquakes. (b) The area along the Ring of Fire is prone to earthquakes. (i) What are earthquakes? Earthquakes are the movements of the Earth’s surface due to a sudden release of energy from the built-up pressure from the friction of the movement between the tectonic plates. (ii) Why is the Ring of Fire prone to earthquakes? This area is made up of the tectonic plate boundaries whereby the plates rub against each other as they move to cause a built-up pressure within. (iii) The magnitude of an earthquake is measured using the Richter scale. If an earthquake is said to have a magnitude of M8.5, how bad would the damages at its epicentre be? Massive destructions with many deaths 3. The figure below shows a huge wave approaching a city. It is a tsunami. (a) What is a tsunami? It is a series of huge waves in the oceans. (b) What causes a tsunami to occur? An earthquake under the ocean Extra Info Tsunamis i Chapter 7 Structure of the Earth and Natural Disasters 131 ©Praxis Publishing_Focus On Science

(c) How does a tsunami wave change as it approaches the shore? It slows down but increases in size as it approaches the shore. 4. On 26 December 2004, a massive undersea earthquake measuring M9.1 struck off the west coast of Sumatra. It triggered a tsunami that hit many countries. The map below shows the epicentre and the affected areas. Africa India Thailand Epicentre Malaysia Indonesia What can you say about the strength of the tsunami based on the affected areas shown on the map? Explain your reason. The tsunami had great strength as it could travel very far, even reaching the African countries. 7.4 Volcanoes 1. (a) What is a volcano? A mountain with an opening in the Earth’s crust through which lava, volcanic ash and gases escape. (b) Where are volcanoes usually found? They are usually found at the tectonic plate boundaries. (c) A volcano usually grows in size as eruptions occur. Briefly explain how this happens. When a volcano erupts, it spews out large amounts of lava down the mountainside. The lava then cools down and solidifies, adding to the size of the volcano. 132 ©Praxis Publishing_Focus On Science

(d) Name the parts of the volcano below. Ash Lava Crater Fissure Central vent Magma Magma chamber 2. There are three types of volcanoes based on their states. Name them and briefly describe their states. Types of volcanoes Description Active volcanoes Have erupted recently and are likely to erupt again Dormant volcanoes Have not erupted in a long time but may erupt in the future Extinct volcanoes Have not erupted in a long time and are unlikely to erupt in the future 3. There are four types of volcanoes based on their shapes. Fill in the blanks to describe each of them. (a) Shield volcanoes A shield volcano is usually very large and has a shape like a warrior’s shield . It has a very broad base and is flat at the top. This type of volcano produces lava that has a low viscosity. The thin lava spreads far from the crater, covering large areas. Chapter 7 Structure of the Earth and Natural Disasters 133 ©Praxis Publishing_Focus On Science

(b) Composite volcanoes A composite volcano has steeper sides compared to a shield volcano. The lava from a composite volcano is very viscous , thus it does not flow far before cooling and solidifying. This creates the steep sides of the volcano. The thick magma can also cause explosive eruptions. (c) Lava dome volcanoes A lava dome volcano is typically circular in shape with a flat top. It has very viscous lava. The lava oozes out of the vent instead of erupting into the air. The lava just piles up over and around the vent forming a dome. When the vent is plugged, the eruptions can be explosive . (d) Cinder cone volcanoes Cinder cones are the most common type of volcano. Most cinder cone volcanoes have a bowl-shaped crater at the top. During an explosive eruption, lava is blown upwards which will cool, solidify and drop as cinders around the vent. 4. Give three responses recommended to people living nearby a volcano during its eruption. Follow instructions given by the authorities on road closures, evacuations and shelter orders. Pay attention to updates from the authorities on hazard zones or any new information on the eruption. Reduce the exposure to volcanic ash by staying indoors. 134 ©Praxis Publishing_Focus On Science

1. Which of the following landforms is not found in Indonesia? A Mountains C Valleys B Rivers D Deserts 2. Why does the Earth’s surface have many natural physical features? A The effects of natural forces such as wind, water and ice B The effects of the Earth’s rotation C The repeated expansion and contraction of the Earth’s surface throughout the day D The reactions of the acid rain 3. Which of the following statements is true about the Earth’s layers? A The crust makes up almost 60% of the Earth’s mass. B The mantle is mostly solid with some molten materials. C The tectonic plates are found in the outer core of the Earth. D The inner core is mainly made up of molten nickel and iron. 4. How do endogenic and exogenic processes differ? A Endogenic process is caused by the Sun while exogenic process is caused by the Moon. B Endogenic process causes weathering while exogenic process causes erosion. C Endogenic process is caused by the internal forces within the Earth while exogenic process is caused by the external forces on the surface of the Earth. Objective Questions A B C D Choose the best answer. D Endogenic process causes the formation of many different landforms while exogenic process destroys the landforms. 5. Which of the following describes erosion and weathering correctly? Erosion Weathering A Breaking down rocks into smaller pieces Transporting pieces of rocks to other places B Transporting pieces of rocks to other places Breaking down rocks into smaller pieces C Breaking down rocks into smaller pieces Breaking down rocks into smaller pieces and transporting them to other places D Breaking down rocks into smaller pieces and transporting them to other places Breaking down rocks into smaller pieces 6. The figure below shows sand dunes in a desert. Which of the following processes contribute to the formation of the sand dunes? I Erosion III Deposition II Weathering A I only C II and III only B III only D I, II and III Chapter 7 Structure of the Earth and Natural Disasters 135 ©Praxis Publishing_Focus On Science

Question 7 is based on the article below. When Dian was a child, she always like to sit on a huge rock at the beach near her house to watch the sunset. She then left her home to further her studies. Later, she worked aboard for a few years. This year Dian returned to her hometown and visited the rock at the beach. She realised that the rock had become smaller and rounder with fewer sharp edges. 7. What do you think happened to the rock in those years? A It underwent some chemical changes due to the seawater. B Nothing happened to the rock as it was Dian who grew up. C It was weathered by the tidal waves. D The intense heat from the Sun caused the rock to become smaller and rounder. 8. Which of the following statements is true about tectonic plates? A The formation of tectonic plates is caused by the cooling surface of the Earth. B The tectonic plates are huge slabs of rock that move slowly. C The tectonic plates are believed to be ancient meteorites from outer space. D The tectonic plates are the solidified magma. 9. Why are the tectonic convergent boundaries considered destructive? A They result in earthquakes and eruptions of volcanoes that damage structures. B They destroy the crust. C They make cracks on the Earth’s surface. D They lift the crust forming mountain ranges. 10. How was the Mariana Trench formed? A By a tectonic plate riding up an adjacent sinking plate B By two tectonic plates moving away from each other C By two tectonic plates sliding past each other D By three tectonic plates colliding at a same point 11.Which of the following are natural disasters due to the movement of tectonic plates? I Earthquakes II Tornadoes III Tsunamis IV Eruptions of volcanoes A I, II and III only C II, III and IV only B I, III and IV only D I, II, III and IV 12.What are the shock waves produced by an earthquake that travel through the ground? A Transverse waves B Microwaves C Seismic waves D Electromagnetic waves 13.Which of the following best describes a tsunami? A A large storm with very high speeds of wind B A type of powerful tornado C A sudden movement of the ground D A large and powerful series of ocean waves 14.Which of the following statements is true about a dormant volcano? A It has erupted recently and is likely to erupt again. B It has not erupted for a very long time and is unlikely to erupt in the future. C It has not erupted for a long time but is likely to erupt in the future. D It has erupted recently but is unlikely to erupt in the future. 136 ©Praxis Publishing_Focus On Science

Complete the concept map below about the structure of the Earth and natural disasters. Concept Map Slow processes Movement of tectonic plates Earthquakes Tsunamis Volcanoes Geomorphic processes Lithosphere Crust Asthenosphere Mantle Mesosphere Outer core Outer core Inner core Exogenic process Endogenic process Divergent boundary Convergent boundary Transform boundary Inner core Weathering Chemical weathering Physical weathering Biological weathering Erosion Deposition Earth’s layers Earth’s structure Landforms Natural disasters based on physical characteristics based on chemical composition types types types types of boundaries examples Chapter 7 Structure of the Earth and Natural Disasters 137 ©Praxis Publishing_Focus On Science

HOTS Daily Application Bali is famous for its consistently powerful tidal waves which are excellent for water surfing activities. However, tidal waves are not the same as tsunamis. How do they differ? Explain your answer from the aspects of the causes, intensity, wave speed and wave period between two consecutive waves. Cause: Tidal waves are caused by the gravitational forces of the Moon and Sun. Tsunamis are caused by undersea earthquakes. Intensity: Tidal waves have less intensity compared to tsunamis. Speed: Tidal waves are slower than tsunamis. Wave period: Tidal waves are a few seconds apart while tsunami waves are 10 minutes to 2 hours apart. Online Quick Quiz 138 ©Praxis Publishing_Focus On Science

Assessment 2 Section A [40 marks] Choose the best answer. Answer all questions. 1. Which of the following describes an electron microscope correctly? I It uses a beam of electrons instead of light. II It creates images with high resolution. III It is small and light, thus it is easy to be carried around. A I only C II and III only B I and II only D I, II and III 2. Which of the following are true about animal and plant cells? I They have a cell membrane, cytoplasm, nucleus and mitochondria. II They cannot be seen with the naked eye. III They carry out life processes. A I and II only B I and III only C II and III only D I, II and III 3. Which chemical is usually used to stain plant cells when they are observed under a microscope in a school laboratory? A Hydrochloric acid B Sugar solution C Iodine solution D Sodium chloride solution 4. Which is not a specialised cell in humans? A Tracheids B Epithelial cells C Ova D Muscle cells 5. Which food is best recommended for a kwashiorkor patient? I Milk II Meat III Rice IV Peanuts A I, II and III only B I, II and IV only C I, III and IV only D II, III and IV only 6. A food is made up of 24 g of fats, 10 g of proteins and 14 g of carbohydrates. What is its energy value in kJ and kcal? Energy value (kJ) Energy value (kcal) A 312 1296 B 272 816 C 1296 312 D 816 272 7. Digestion of proteins occurs in the I mouth II stomach III small intestine IV large intestine A I and II only C II and III only B I and III only D III and IV only 8. The figures show two types of blood cells. W X Assessment 2 139 ©Praxis Publishing_Focus On Science

Which is correct about blood cells W and X? W X A Have many sizes and shapes Have a biconcave shape B Found only in deoxygenated blood Found only in oxygenated blood C Carry carbon dioxide Carry oxygen D Destroy germs Clot blood at injury sites 9. What causes a heart attack to occur? A The heart has difficulties pumping blood to the whole body. B A hard blow lands on the heart. C The supply of blood to the heart is blocked. D The nicotine from cigarette smoke makes the heart work too hard. 10. If a hole is made in the human chest wall, the person might not be able to breathe even if his lungs are not damaged. Why does this happen? A The lungs do not work when they are exposed to the atmosphere. B Carbon dioxide from the atmosphere enters the lungs from the hole. C The person may lose too much blood. D The air pressure in the thoracic cavity is equal to the atmospheric pressure. 11. The figure below shows a situation in a public area. Who are the passive smokers? A P and Q C Q and R B P and R D P, Q and R Questions 12 and 13 refer to the figure below that shows one of the human excretory organs. M N O P 12. What are structures N, O and P? N O P A Vein Artery Urethra B Artery Vein Urethra C Vein Artery Ureter D Artery Vein Ureter 13. What is the function of structure M? I Filters waste materials from the blood II Regulates the level of mineral salts III Regulates body temperature A I only C II and III only B I and II only D I, II and III 14. In which situation is work not done? A Sitting on a chair while listening to music B Carrying a bag to the door C Lifting a book from the floor D Pushing a trolley along the racks 15. Ahmad has a mass of 50 kg. He is carrying a bag of 5 kg while climbing 4 m up a tree in 10 seconds. 5 kg 4 m 140 ©Praxis Publishing_Focus On Science

What is the power generated by Ahmad? (1 kg = 10 N) A 2 W C 22 W B 20 W D 220 W 16. Solar energy, biomass energy and wind energy are renewable energy sources because they A originate from the Sun B do not pollute the environment C can be replenished D can generate electricity 17. The figure shows a ball with a mass of 200 g moving with a speed of 10 m s–1. 10 m s–1 Find the kinetic energy possessed by the ball. (1 kg = 10 N) A 10 J C 100 J B 20 J D 10 000 J 18. Which are true about third-class levers? I The fulcrum is between the effort and the load. II The mechanical advantage is always less than one. III They increase the amount of work done. A II only C II and III only B I and II only D I, II and III 19.What form of energy does a bird resting on a tree branch have? A Kinetic energy B Elastic potential energy C Gravitational potential energy D Sound energy 20. In an experiment, Nik observed that a simple pendulum completed 20 oscillations in 50 seconds. What are its period and frequency? Period (s) Frequency (Hz) A 2.5 0.4 B 0.4 2.5 C 1000 0.001 D 0.001 1000 21.Which is not true about electromagnetic waves? A They do not require a medium to travel. B They travel at the speed of light which is 3 × 108 m s–1. C They contain an electric field and a magnetic field. D Sound waves and seismic waves are examples of electromagnetic waves. 22.When a key on a piano is struck, it gives out a loud, high-pitched sound. Which of the following graphs represents the sound wave? A Displacement (cm) O Time (s) B Displacement (cm) O Time (s) C Displacement (cm) O Time (s) D Displacement (cm) O Time (s) Assessment 2 141 ©Praxis Publishing_Focus On Science

23.Which of the following animals use echolocation to determine the locations of their prey? I Bats II Dolphins III Whales A I only C I and III only B III only D I, II and III 24. The figure shows a light ray reflected by a plane mirror. Plane mirror 60° What is its angle of incidence? A 30° C 50° B 40° D 60° 25. It is given that a glass is denser than water. Which is the correct path of the refracted ray when it travels from water into the glass as shown in the figure? Water A B C D Glass Normal 26.Which is true about the charges of an electron, a neutron and a proton? Electron Neutron Proton A Negative Positive Neutral B Positive Neutral Negative C Negative Neutral Positive D Neutral Negative Positive 27. The following shows the information on a group of elements in the Periodic Table. • Also known as alkali metals • Consists of lithium, sodium, potassium, rubidium, caesium and francium What is the group? A Group 1 C Group 17 B Group 2 D Group 18 28. The figures show four types of substances. W X Y Z Which are compounds? A W and Y C X, Y and Z B X and Y D W, X, Y and Z 29. The figure shows the pH values of three substances. 1 2 3 4 5 6 7 8 9 10 11 12 W X Y 13 Which of the following correctly represents W, X and Y? W X Y A Lemon Detergent Distilled water B Distilled water Lemon Detergent C Lemon Distilled water Detergent D Detergent Distilled water Lemon 142 ©Praxis Publishing_Focus On Science

30. How are mixtures and compounds different? A Mixtures can be separated but compounds cannot be separated. B Mixtures are man-made but compounds are found in nature. C Mixtures have fixed properties but compounds do not have fixed properties. D Mixtures have no fixed boiling points but compounds have fixed boiling points. 31. The figure shows an apparatus set-up to separate water from a salt solution. Thermometer Distillation flask Water out Liebig condenser Water in Salt solution Bunsen burner What is this method of separation known as? A Filtration B Distillation C Chromatography D Sublimation 32. The following information shows the properties of a liquid. • Tastes sour • Corrosive • Has a pH value of 5 Which is true about the liquid? A It reacts with magnesium to produce bubbles. B It is alkaline. C It turns red litmus paper blue. D It has a soapy feel. 33. Which is not a pH indicator? A Iodine solution B Litmus solution C Universal indicator D Methyl orange 34.What is added to acidic soil to neutralise it? A Slake lime C Vinegar B Lime D Hydrochloric acid 35. The figure shows the layers of Earth. T Which is true about layer T? A It is mainly made up of molten iron and nickel. B It contains the tectonic plates. C It is the hottest layer. D It is the thickest layer. 36. How is weathering different from erosion? A Weathering changes the surface of the Earth while erosion changes the inner layers of the Earth. B Weathering can be carried out physically, biologically and chemically while erosions only can be carried out chemically. C Weathering happens naturally while erosion is man-made. D Weathering involving the breaking down of rocks while erosion involves the transportation of weathered rocks. 37.Which of the following landforms form due to deposition? A Mountains C Rivers B Deltas D Islands Assessment 2 143 ©Praxis Publishing_Focus On Science

38.What are usually formed at a divergent boundary? I Mid-ocean ridges II Mountain ranges III Continental rifts A I only B I and III only C II and III only D I, II and III 39.A massive earthquake occurred in Turkiye and Syria on 6 February 2023, killing more than 50 000 people. This area is prone to earthquakes. Why is it so? A Its ground is very soft and not stable. B It sits on a boundary between multiple tectonic plates. C It is situated on a very big tectonic plate. D It sits on a tectonic plate that is moving constantly. 40.Which is not a possible cause of tsunamis? A Undersea earthquakes B Undersea volcanic eruptions C Undersea massive landslides D Undersea pipeline ruptures Section B [60 marks] Answer all questions. 1. The figure shows a pair of specialised cells found in the leaves of green plants. (a) What are specialised cells? They have special shapes and structures to carry out special functions. [1 mark] (b) (i) Name the specialised cells shown above. Guard cells [1 mark] (ii) State the function of the specialised cell. To regulate the gas exchange between the plant and the atmosphere [1 mark] (iii) Briefly explain how these cells function. Each pair of guard cells control the opening of the stoma (pore) that allows the gases to move in and out of the plant. [1 mark] 144 ©Praxis Publishing_Focus On Science

(c) State another two types of specialised cells found in plants. Phloem and xylem (or any other suitable answer) [2 marks] 2. (a) There are two types of digestion, namely physical digestion and chemical digestion. How do they differ? Physical digestion involves the breakdown of pieces of food into smaller pieces. Chemical digestion involves the breakdown of complex food molecules into simple molecules with the help of enzymes. [2 marks] (b) The figure shows the human liver. (i) What does the liver produce to help in food digestion in humans? Bile [1 mark] (ii) How does the product help in food digestion? The bile emulsifies fat into small droplets and creates an alkaline condition for the pancreatic enzymes to work. [2 marks] (iii) Rudy’s liver is not working well. Which type of food digestion will be affected? Digestion of fat [1 mark] 3. The figure shows two workers lifting two similar bags of cement from the ground to the third floor. Each bag of cement weighs 65 kg. The height of the third floor from the ground is 40 m. 65 kg Worker Q Worker P 65 kg Assessment 2 145 ©Praxis Publishing_Focus On Science

(a) Define work done. Work done is defined as the force exerted on an object multiplied by the distance the object moves in the direction of the force. [1 mark] (b) Calculate the work done by worker P in lifting the bag of cement to the third floor. [1 kg = 10 N] Work done = mgh = 65 × 10 × 40 = 26 000 J [2 marks] (c) Is the work done by worker P the same as the work done by worker Q? Explain. No. Worker P lifted only the bag of cement to the third floor. Worker Q lifted the bag of cement and himself to the third floor. Worker Q did more work than worker P. [2 marks] 4. The figure below shows a water molecule. Hydrogen Hydrogen Oxygen (a) Name the elements that make up a water molecule in the figure above. [3 marks] (b) (i) Is water a compound or a mixture? A compound [1 mark] (ii) Explain your answer. A water molecule has a fixed ratio of the number of hydrogen atoms and oxygen atoms. (or any other suitable answer) [1 mark] (c) How can the elements in the water molecule be separated? By electrolysis [1 mark] 146 ©Praxis Publishing_Focus On Science

5. Yanti carried out a neutralisation reaction between hydrochloric acid and sodium hydroxide solution. She recorded the pH values of the hydrochloric acid when the sodium hydroxide solution was added to it. Based on her results, she plotted a graph as shown below. 14 pH value Volume of sodium hydroxide (cm3 ) 12 10.0 20.0 30.0 40.0 50.0 10 8 6 4 2 0 (a) State the pH value of the hydrochloric acid before the sodium hydroxide solution was added. 1 [1 mark] (b) Based on the graph, how much sodium hydroxide solution was needed to neutralise the acid? 25 cm3 [1 mark] (c) Name the method used by Yanti. Titration [1 mark] (d) What happens when the acid was neutralised by the sodium hydroxide solution? The sodium hydroxide solution completely cancelled out the effects of the acid. [1 mark] (e) Why did the pH value of the solution increase at the end of the experiment? There was more alkali (sodium hydroxide solution) than acid. Thus, the solution is alkaline and has a pH value of more than 7. [2 marks] (f) Write a word equation to represent the neutralisation reaction that was carried out. Hydrochloric acid + sodium hydroxide → sodium chloride + water [2 marks] Assessment 2 147 ©Praxis Publishing_Focus On Science