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Snapask Intensive Course PSLE Science

Author | Snapask TeamPublisher | Snapask (Holdings) Pte. Ltd.©Snapask Singapore 2021

Contents P. 6Course Flow, Learning Objectives, Be Exam-Ready

P. 7Examination Format

P. 8-15General Exam Tips

P. 16-17Matter

P. 11-23States of Matter

P. 24-25Changes in States of Water

P. 26-32Water Cycle

P. 33-34Life Cycle of Flowering Plant

P. 35-38Growth of Seed

P. 39-40Seed Dispersal

P. 41-46Sexual Reproduction of Flowering Plants

P. 47-51Magnets

P. 52Gravitational, Elastic Spring & Frictional Force

P. 53-59Push or Pull

P. 60-61Different Forms of Energy

P. 62-71Energy Conversion

P. 72-116Mock Exam I

P. 117-122Mock Exam I - Answers

P. 123-159Mock Exam II

P. 160-164Mock Exam II - Answers

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Course Flow z Be Exam-ready (Tips & Strategies) z Cycles in Matter and Water z Cycles in Plants z Interaction of Forces z Energy Forms and Uses z Mock Exams 1 & 2

Learning Objectives z To obtain exam tips and strategies for each paper z To uncover common mistakes by reviewing and answering past

year questions z To understand key concepts

Be Exam-Ready z Arrive early for the examination z Visit the toilet z Be calm and collected z Make sure you have the necessary stationery and other items such as

the entry proof, NRIC/student card and water bottle z Listen carefully to the examiners and their instruction z Manage your time well - Aim to finish 10 minutes ahead of time for

the written papers so that you can check your answers for spelling, grammar and punctuation errors

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Reference: SEAB.Gov.sg

Examination Format

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PSLE Science General Exam Tips

Explanation Questions

z A common way students lose marks in open-ended explanation questions is by writing incomplete answers.

z One way to make sure that your answer is complete is to check whether your answer is linked to the question.

z This can be done in 4 steps:◊ Think of a short answer to explain the scenario.◊ Highlight the keywords in your answer.◊ Read the question again and highlight the keywords in

the question.◊ Link the keywords in your answer to the keywords in the question

using general scientific concepts.

ExampleA huge sponge can be squeezed into a small ball. Give a reason for this.

Short answer: There is trapped air in the sponge.

Highlight key words in answer: There is trapped air in sponge

Highlight key words in question: A huge sponge can be squeezed into a small ball.

Link keywords: air squeezed air has no definite volumeair huge, small air can be compressed

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Final answer: There is trapped air in a sponge. Air has no definite volume and can be compressed. Hence, a huge sponge can be squeezed into a small ball.

Comparative Terms

z Examples of comparative terms are: some, less, more, larger, smaller, hotter, colder etc.

z We use comparative terms in most of our answers to open-ended questions. This is because most things in science are not absolute.

z Example:At night, we cannot see many things because there is no light reflected into our eyes.

‘No light’ is an absolute statement. This is a wrong statement because there is always some reflected light from the stars or the moon that goes into our eyes.

Correct statement: At night, we cannot see many things because there is very little light reflected into our eyes.

Explanation Questions

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Data-based or Information-based Questions

z Data-based questions are questions where data is given in the form of table, graph or diagram.

z You will be asked to choose the correct option and explain how you choose using the data given.

z Once again, incomplete answers are quite common in these types of questions because students do not use data given in the question in their answer.

z A complete answer can be written by following these 3 steps:◊ Choose the correct option◊ Link question to general scientific concepts ◊ Link used data to the same general scientific concepts

z Example:Three rods of the same length but different materials are heated at the bottom of the rod using the same heater. After 1 minute, the temperature at the top of each rod is measured. The recorded results are shown in the table. The initial temperature at the top of each rod is 30°C.

Material Temperature at the top after one minute (°C)A 40B 50C 60

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Based on the table, which material is the most suitable to be used as the handle of a cooking pot? Explain your answer.

Choose the correct option: Material A

Link question to general scientific concepts: The handle of a cooking pot needs to be a poor conductor of heat so that our hands are not burnt when handling a hot pot.

Link data to the same concepts: The increase in temperature at the top of material A after one minute is the lowest. This makes Material A the poorest conductor of heat among these three*.

Final answer: Material A. The handle of a cooking pot needs to be a poor conductor of heat so that our hands are not burnt when handling a hot pot. Since the increase in temperature at the top of material A after one minute is the lowest, Material A is the poorest conductor of heat among these three. Hence, Material A is the most suitable material to be used as the handle of a cooking pot.

z Sometimes, information given to you may not be in the form of data. It can be descriptions or pictures. It doesn’t matter, you still can answer them using the 3 steps above.

z There are similar types of questions where information is also given to you in the form of diagrams, tables or graphs. But you are not asked to choose anything. The question asks you to do something else instead. It can be suggesting improvements, explain the trend observed in data,


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etc. We still can use similar tricks. Instead of performing all 3 steps, we just do the last 2.

◊ Link question to general scientific concepts◊ Link used data to the same general scientific concepts

You then use the linkage made to answer the question.

Experimental Questions

z Experimental questions are extremely popular these days, in both MCQs and open-ended questions.

z There are many things they can ask when it comes to experimental questions. They may ask you to describe the experiment, explain the results, improve the experiment etc.

z The following terms are often used in experimental questions:◊ Aim◊ Changed variable◊ Measured variable◊ Controlled variable◊ Hypothesis◊ Control set up

z The changed variable is the variable which is tested. The measured variable is something measured to find out the effect of changing the changed variable. The changed variable is the ‘cause’ and the measured variable is the ‘effect’.


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z There can only be one changed variable and one measured variable in one experiment. However, there can be more than one experiment in one question. So there can be more than one changed variable or one measured variable in a question.

z To ensure that the experiment is a fair test, every other variable which can affect the measured variable must be kept constant. They are called the controlled variables.

z The aim of the experiment is often written as ‘to find out how (changed variable) affects (measured variable)’.

z Hypothesis is a prediction of the experiment. This prediction does not need to be correct. In fact, the reason why an experiment is carried out is to test the hypothesis. Hypothesis is an answer to the aim which we don’t know whether it’s correct or not. So one way to formulate a hypothesis is by first knowing the aim of the experiment. When formulating hypotheses, remember to use comparative terms.

z The purpose of a control set up is to ensure that only the changed variable will affect the measured variable. A simple way to have a control set up is to remove the changed variable from the experimental set up, keeping everything else constant.

z Regardless of the types of questions they ask, the first step we need to do is to understand the experiment, which can be challenging to many students under time pressure.


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z However, understanding experiments is not hard as long as we are systematic in the way we think.

z To understand an experiment, we just need to do the following 5 steps:◊ Identify the aim of the experiment◊ Identify the changed variable, the measured variable and the

controlled variables◊ Analyse the results◊ Identify the general scientific concepts◊ Link the scientific concepts to the results

z If the question ask how you can improve the experiment, we can look into◊ More effective ways to change the changed variable◊ How to measure the measured variable more accurately◊ Other variables not kept constant in the question which should be

kept constant◊ Perform each measurement at least 3 times and find the average

value of the multiple measurements. This is to ensure that the results are consistent and no errors were made during measurements.

z To describe the trend of the results, we can always phrase the answer as: The (measured variable) increases/decreases when the (changed variable) increases.


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PSLE SCIENCE STUDY NOTES

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Cycles in Matter and Water

Matter

z Matter has mass and occupies space.

z Mass is the amount of matter in an object. It is measured in grams (g) or kilograms (kg). We use a balance to measure the mass of objects.

z The amount of space occupied by an object is measured by its volume. Volume is measured in cubic centimetres (cm3), millilitres (ml) or litres (l). Volumes can be measured using a measuring cylinder.

A measuring cylinderA balance

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Matter

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States of Matter

z There are three states of matter: solid, liquid and gas.

z A solid has a definite volume and shape. It has a fixed shape and size.

z A liquid has a definite volume but no definite shape. It takes the shape of the container.

z Gas has no definite shape and volume. It takes the shape of the container and occupies the whole volume of the container.

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Common mistakes

Example 1The diagram below shows a beaker containing 500 cm3 of water. A metal block is placed inside the beaker as shown. The water level rises to 800 cm3.

Which of the following statements is correct?

(1) The volume of the metal block is 300 cm3.(2) The volume of the metal block is more than 300 cm3.(3) The volume of the metal block is less than 300 cm3.(4) The volume of the metal block is 800 cm3.

Common answer students pick: (1)

States of Matter

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States of Matter

Option (1) is incorrect because the metal block is not fully submerged in water. The volume of 300 cm3 does not include the volume of the portion of the block outside the water as shown in the diagram below.

Hence, the correct answer should be Option (2)

Example 2When a small stone is dropped into a container of water, the water level rises. A student claims that there is now more water in the container.

Do you agree with the student? Explain your answer.

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Keywords in answer: No, the volume of water remains the same. The water level rises because the small stone pushes the water up.

Keywords in question: When a small stone is dropped into a container of water, the water level rises. A student claims that there is now more water in the container.

Link keywords: Volume of water remains the same more water in the container (wrong) water has definite volume

Small stone pushes the water up small stone dropped into water stone occupies space

Here’s the correct answer: No. The student is wrong because water has definite volume and hence, the volume of the water does not change. The water level rises because the small stone occupies space in the container, pushing the water up.

States of Matter

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Practice

Question 1Pete has three cubes of the same sizes as shown in the diagram below.

Which of the following statements about the cubes is incorrect?

(1) They are made of different types of materials.(2) They occupy the same amount of space.(3) They have the same shape.(4) They have the same mass.

States of Matter

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Question 2The diagram shows a solid wooden ball (no air in the ball) of volume 100 cm3. The ball is then crushed into pieces.

Will the total volume of the crushed pieces be different from the volume of the wooden ball at the start? Explain your answer. [2 marks]

States of Matter

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Changes in States of Water

z At 100°C, pure water changes from liquid to gaseous state, steam, at the constant temperature of 100°C, in a process called boiling. Water gains heat energy during this process. 100°C is the boiling point of water.

z Water can also change from liquid to gaseous state, water vapour, through evaporation. Evaporation takes place at any temperature between 0°C and 100°C. Water gains heat energy from the surroundings during this process. Unlike boiling, evaporation causes water to cool down.

z Evaporation depends on WHAT:W – Wind. Water evaporates faster when there’s wind.H – Humidity. Water evaporates faster when surrounding air is less humid.A – Area of water exposed to air. Water evaporates faster if a larger area is exposed to air.T – Temperature of water. Water evaporates faster if water is hotter.

z When a water vapour or steam is cooled, it changes from gaseous state to liquid state, water, through condensation. The water vapour or steam loses heat energy during this process.

z When the temperature of water falls to 0°C, pure water changes from liquid to solid state, ice, in a process called freezing. Water loses heat energy during this process.

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Changes in State of Water

z When the temperature of ice rises to 0°C, ice changes from solid state to liquid state, water, though melting. Ice gains heat during this process. 0°C is known as the melting point of ice or freezing point of water.

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Water Cycle

z Water cycle is the continuous movement of water from the Earth to the atmosphere and back to Earth. This is possible since water can change from one state to another.

z First, heat energy from the sun causes water to evaporate faster to form water vapour.

z The water vapour rises into the sky. It then condenses into water droplets. The water droplets gather to form clouds.

z When there are enough water droplets in the cloud, the cloud becomes heavy. Precipitation occurs and the water droplets fall to the ground as rain.

z The water on the ground evaporates due to heat energy from the sun and the cycle repeats.

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Water Cycle

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Common mistakes

Example 3An experiment was set up to study how evaporation depends on the type of container used. Containers A, B and C are filled with the same amount of water.


The volume of water in each container is measured after one hour.


(1) Container A has the most amount of water left.(2) Container B has the most amount of water left.(3) Container C has the most amount of water left.(4) All containers have the same amount of water left.


Water Cycle

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Option (2) is incorrect. The evaporation of water depends on the area of water exposed to the air. Not the size of the mouth of the container. Container A has the lowest area of water exposed to the air hence will experience the slowest evaporation. Hence container A will have the most amount of water left after 1 hour.

Hence, the correct answer should be Option (1).

Exam Trick

Explaining why water droplets are observed in different situations is a common question asked in exams. The source of warm water vapour and cold surface can be different but the concepts involved are the same. We can use the following structure to answer these types of questions:

The warmer water vapour from (source) comes into contact with the cooler surface of (object). It then loses heat and condenses to form water droplets.

More generally, for questions involving change of states of water, always include: What is warmer? What is colder? Heat gain or heat lost?

Water Cycle

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Example 4Explain why water droplets are observed on the bathroom mirror when a person takes a hot shower.

Common answer students write: Water vapour from the surrounding air comes into contact with the mirror and condenses to form water droplets.

The answer is incomplete because it does not explain why condensation happened. Condensation only happens when WARMER water vapour comes into contact with a COOLER surface and LOSES HEAT. Let’s use the trick to answer this.

Here’s the correct answer: The surrounding air gains heat from the hot water during the shower. The warmer water vapour from the surrounding air comes into contact with the cooler surface of the mirror. It then loses heat and condenses to form water droplets.

Water Cycle

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Practice

Question 3Which of the following shows the correct difference between boiling and evaporation?

Question 4A cooking pot with a lid is used to cook soup. Explain why water droplets are observed on the inner side of the lid after cooking. [2 marks]

Water Cycle

Boiling Evaporation(1) Water changes to steam when

water gains heat.Water changes to water vapour when water loses heat.

(2) Water changes to steam when the temperature of water reaches 100℃.

Water changes to water vapour at any temperature between 0℃ and 100℃.

(3) Hot water vapour condenses to form steam when cooled.

Hot water vapour condenses to form water at any time.

(4) Steam loses heat when steam condenses.

Water vapour gains heat when water vapour condenses.

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Practice Questions’ Answers

Question 1: (4)Question 2: No. Solids have definite volume. Since the crushed pieces

come from the same ball, the total volume will remain the same even if it is broken into many pieces.

Question 3: (2)Question 4: When the soup is cooked, the soup becomes warm.

Warmer water vapour from the warm soup rises and comes into contact with the cooler inner surface of the lid. The hot steam loses heat and condenses to form water droplets.

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Cycles in Plants

Life Cycle of a Flowering Plant

z All plants must reproduce so that their species live on after they die.

z Flowering plants such as sunflower and mango tree bear fruits, which contain seeds.

z The seeds grow into seedlings, which grow into adult plants. The adult plants grow flowers. The flowers turn into fruits, which contain seeds and the cycle repeats.

z Only flowering plants reproduce with seeds. Non-flowering plants reproduce with spores.

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Life Cycle of a Flowering Plant

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Growth of Seed

z Each seed requires WOW to germinate and grow.W – WaterO – OxygenW – Warmth

z Light is not needed as seed leaves provide food for the young plant.

z The roots of a seed will grow downwards first to take in water.

z The shoots will grow upwards next and develop true leaves. The plant can now make its own food through photosynthesis and no longer needs seed leaves.

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Common mistakes

Example 1In what direction is food and water transported in a plant?


Option (1) is incorrect because both the roots and the shoots of the plant needs food. So food also travels upwards so that the shoot can grow.


Example 2A seedling does not depend on seed leaves for food. Explain why.

Food Water(1) Upwards Downwards(2) Upwards and Downwards Downwards(3) Downwards Upwards(4) Downwards Upwards and Downwards

Growth of Seed

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Common answer students write: Because a seedling has true leaves.

The answer is incomplete because the answer is not linked to the question. Let’s try the linking method.

Short answer: Because a seedling has true leaves.

Keywords in answer: Because a seedling has true leaves.

Keywords in question: A seedling does not depend on seed leaves for food.

Link keywords: True leaves for food leaves have chlorophyll and can produce food through photosynthesis

Here’s the correct answer: A seedling has true leaves. The true leaves contain chlorophyll, which can carry out photosynthesis by trapping sunlight. Photosynthesis produces food for the seedling.

Growth of Seed

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Practice

Question 1Daniel planted a mango seed in a pot and placed the pot in a fridge. He waters the mango seed daily. The seed did not germinate. Which of the following could be the reason?

(1) There’s not enough sunlight in the fridge.(2) There’s too little space for the seed to germinate.(3) The soil lacks nutrients.(4) The soil is too cold.

Question 2The diagram below shows different stages of growth from a seed to an adult plant.

Arrange the growth of the plant in the correct order. [1 mark]

_____ _____ _____ _____ _____ _____

Growth of Seed

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Method of Seed Dispersal

Seed characteristics Example

Animals z Edible fruits with small indigestible seeds which are passed out as droppings. E.g. guava

z Edible fruits with large seeds which are thrown away after eating. E.g. mango

z Hooks that cling onto furs or hair

Mimosa

Splitting z Pod-like structure

Pod of flame of the forest

Seed Dispersal

z Plants disperse their seeds to prevent overcrowding.

z When overcrowding happens, the young plants need to compete with the parent plants for space, water, nutrients and sunlight.

z The four methods of seed dispersal and their characteristics are summarised in the table below.

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Method of Seed Dispersal

Seed characteristics Example

Wind z Light z Wing-like, feather-like or

parachute-like

Dandelion

Water Fibrous husks to trap air so that seeds can float on water

Coconut

Seed Dispersal

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Sexual Reproduction of Flowering Plants

z Sexual reproduction of flowering plants begins with pollination. Pollination is the transfer of pollen grains from the anther to a stigma of a flower. If the pollen grain comes from the anther of the same flower or another flower from the same tree, self-pollination takes place. If the pollen grain comes from the anther of another flower from another free, cross-pollination takes place.

z After pollination, a pollen tube is developed through the style and moves towards the ovary.

z Fertilisation occurs when the male reproductive cell from the pollen grain fuses with the female egg cell in the ovule to form a fertilised egg.

z After fertilisation, the ovary develops into a fruit and the ovule develops into seeds.

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Flower Location of Pollen GrainsA Anther of the same flowerB Anther of another flower from the same plantC Anther of another flower from another plant

Common mistakes

Example 3The stigmas of Flowers A, B and C receive pollen grains from three different locations. The table below shows the location of the pollen grains.

Which of the following shows the correct type of pollination for each plant?


Option (2) is incorrect because cross-pollination is the transfer of pollen grains from the anther of a flower to the stigma of a flower across two different plants. Since for Flower B, the anther is found from the same plant, self-pollination happens for Flower B.


Flower A Flower B Flower C(1) Self-pollination Self-pollination Cross-pollination(2) Self-pollination Cross-pollination Cross-pollination(3) Cross-pollination Cross-pollination Cross-pollination(4) Cross-pollination Cross-pollination Self-pollination


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Example 4The diagram below shows the position of a parent plant and its seedlings.

Based on the diagram above, identify the method of seed dispersal of the parent plant. Explain your answer.


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Common answer students write: The seeds are dispersed by wind. This is because the seeds are light and have wing-like or feather-like structures.

This is a data-based question. The answer is incomplete because it does not use information given in the diagram. Let’s use what we learned to tackle data-based questions.

Choose the correct option: Dispersal by wind

Link question to general scientific concepts: seed dispersal method seed characteristics light and have wing-like or feather-like features.

Link data to the same concepts: The diagram shows that the seeds are found far away from the parent plant in the direction of the wind. Seed characteristics allow them to stay in air for long periods of time and follow the direction of wind.

Here’s the correct answer: The seeds are dispersed by wind. The diagram shows that the seeds are found far away from the parent plant in the direction of the wind. Seeds dispersed by wind are light and have wing-like or feather-like features. This allows them to stay in air for long periods of time and follow the direction of wind.


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Practice

Question 3Which of the following is incorrect?

Question 4The diagram below shows two flowers.

Which flower can self-pollinate? Explain your answer. [2 marks]


Plant Method of Seed Dispersal(1) Papaya Animals(2) Coconut Water(3) Rubber Splitting(4) Mango Wind

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Question 1: (4)Question 2: E, B, D, A, F, CQuestion 3: (2)Question 4: Flower A. It has both the male and female reproductive

organs. The pollen grains from Flower A can be transferred to the female stigma of Flower A.

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Magnets

Interaction of Forces

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z All materials are either magnetic materials or non-magnetic materials.

z Magnetic materials can be made into magnets or attracted to magnets. Examples of magnetic materials are iron, steel, nickel and cobalt.

z Non-magnetic materials cannot be made into magnets and do not interact with magnets. Examples of non-magnetic materials are aluminium, brass, glass and paper.

z Magnets always attract magnetic materials.

z Magnets can attract or repel other magnets. Magnets have two poles: North pole and South pole. Like poles of two magnets repel each other, unlike poles of two magnets attract each other.

z A freely hanging magnet will rest in the North-South direction.

z A magnet’s magnetism can pass through non-magnetic materials.

Magnets

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Common mistakes

Example 1A pile of rubbish consists of plastic pieces and iron pieces. Amanda would like to separate the iron pieces from the plastic pieces so that she can recycle the iron. She moves a bar magnet over the pile of rubbish to separate the iron from the plastic.

Which of the following concepts did Amanda use to separate iron from plastic?

A. Unlike poles of two magnets attract.B. Magnetic forces can act at a distance.C. Magnets always attract magnetic materials.D. Magnet always come to rest in a North-South direction.

(1) A and D only(2) B and C only(3) B, C and D only(4) A, B, C and D


In this question, all four concepts given are correct statements. However, the question asked for the concept Amanda used to separate iron from plastic. Even though Concepts A and D are correct, Amanda did not use the concepts.


Magnets

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Magnets

Example 2A thin paper sheet is placed between a magnet and a steel paper clip. Can the magnet attract the steel paper clip? Explain your answer.

Common answer students write: Yes. This is because magnetism passes through any thin materials.

The answer is incorrect because magnetism only passes through non-magnetic materials. It also does not explain why after magnetism passes through the paper, the magnet can attract the paper clip.

Here’s the correct answer:Yes. Magnetism passes through non-magnetic materials. Since the paper sheet is a non-magnetic material, magnetism of the magnet can pass through it to attract the steel paper clip, which is a magnetic material.

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Magnets

Practice

Question 1Bar P and Bar Q repel each other when they are brought together. Which of the following statements is correct?

(1) Bar P is a magnet and Bar Q is a magnetic material.(2) Bar P is a magnet and Bar Q is made of copper.(3) Bar P and Bar Q are both magnets.(4) Bar P and Bar Q are both magnetic materials.

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Gravitational, Elastic Spring and Frictional Force

z Gravitational force acts on objects on Earth at all times. It is a downward force pulling an object towards the Earth.

z Elastic spring force is the force acting on a stretched/compressed object to return the object to its original shape. The force is larger when an object is stretched/compressed more.

z Frictional force is the force which opposes motion. Friction due to air is also known as air resistance. Friction due to air is also known as air resistance while friction due to water is known as water resistance. Friction is greater on a rough surface or when the object is pressed harder against the surface.

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Push or Pull

z A force is a push or pull.

z Humans are not the only ones that have the ability to push or pull. Many other things, e.g. air and water, can also push objects.

z Other than the normal push and pull, there are four main types of forces: gravitational force, frictional force, magnetic force and elastic spring force.

z Gravitational force and magnetic force can act at a distance. Frictional force and elastic spring force only act when in contact.

z The effect of forces on an object is summarised in the flowchart.

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Push or Pull

Exam Trick

Many students struggle to answer questions when there are two or more forces involved. The first thing we need to do to tackle these types of questions is to identify the effect of two or more forces on an object. Students can take the following steps to answer these questions:

Identify the type of forces acting on the object.1. Group the forces into four directions: up, down, left or right.2. Check whether there are forces at 90o to the surface. They will not

affect the object.3. Identify which group of forces is stronger. That will be the direction of

the combined force.4. Use the flowchart to identify the effect of the combined force.

Question 2Ivan presses a plasticine ball against the table. He notices that the ball becomes a flat disk.

What is the effect of the force applied on the plasticine ball? [1 mark]

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Difficult Questions

Example 3The force needed to throw Object A upwards is greater than the force needed to push Object A on the floor to the right. Explain the difference.

Let’s use the trick introduced.

Object A thrown upwards:1. There are three forces: gravitational force, air resistance and pushing

force from the person.2. Gravitational force and air resistance are downwards, pushing force

from the person is upwards.3. There is no surface.4. Upward force greater than downward force.5. Object initially at rest. Hence, object starts moving upwards.

Object A pushed on a floor:1. There are three forces: gravitational force, friction due to floor and

pushing force from the person.2. Gravitational force is downwards, friction is to the left, pushing force

from the person is to the right.3. Gravitational force is 90o to the surface. It will not affect the object.4. Force to the right greater than force to the left.5. Object initially at rest. Hence, object starts moving to the right.

With this analysis, we are ready to answer the question.

Push or Pull

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Here’s the answer: To throw object A upwards, the pushing force from the person must be greater than both the gravitational force and the air resistance acting on the block. To move object A on the floor to the right, the pushing force only needs to be greater than the friction due to the floor. Hence, a greater force is needed to push object A upwards than to push the object on the floor to the right.

Example 4Sandy throws a ball upwards. After the ball leaves the hand, she notices that the ball slows down. Explain her observation.

Let’s use the trick introduced.

After Object A leaves the hand:1. There are two forces: gravitational force and air resistance.2. Gravitational force and air resistance are downwards.3. There is no surface.4. There are only downward forces.5. Object initially moves up. Hence, object starts to slow down.

Here’s the answer: After the ball leaves the hand, the ball experiences gravitational force and air resistance. Both forces are acting downwards. Since the ball is initially moving up, the direction of force opposes the direction of motion. Hence, the ball slows down.

Push or Pull

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Question 3A box is being pushed as shown in the diagram below.

Which pair of arrows shows the correct direction of gravitational force and frictional force?

Push or Pull

Gravitational force Frictional force(1) R P(2) R Q(3) S P(4) S Q

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Question 4After a car brakes, the car will travel a certain distance before stopping. This distance is known as the braking distance.

Would the braking distance be longer or shorter on a wet road compared to a dry road? Explain your answer. [2 marks]

Push or Pull

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Question 1: (3)Question 2: The force changes the shape of the ball.Question 3: (2)Question 4: Longer. On a wet road, there is less friction. It would be

harder for the car to stop. Hence, the car needs to travel a longer distance before stopping.

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Energy Forms and Uses

Different Forms of Energy

z There are various forms of energy.◊ Kinetic energy◊ Gravitational potential energy◊ Chemical potential energy◊ Elastic potential energy◊ Light energy◊ Electrical energy◊ Sound energy◊ Heat energy

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z Kinetic energy is the energy due to the motion of an object. It depends on the mass and the speed of the object. If the object has a heavier mass, the kinetic energy is greater. If the object has a faster speed, the kinetic energy is greater.

z Gravitational potential energy is the energy due to the position of an object in a gravitational field. It depends on the mass and the height of the object from the ground. If the object has a heavier mass, the gravitational potential energy is greater. If the object has a greater height from the ground, the gravitational potential energy is greater.

z Chemical potential energy is the energy stored in food, fuels and batteries.

z Elastic potential energy is the energy stored in stretched or compressed objects.

z Light energy is the energy emitted by light sources. Light energy allows us to see when light is reflected into our eyes.

z Electrical energy is the energy transferred in an electrical circuit.

z Sound is a form of energy that allows us to hear. Sound can travel through solids, liquids and gases. Sound energy can be produced by friction.

z Heat energy is an energy that flows from a region of higher temperature to a region of lower temperature. Heat energy can also be produced by friction.

Different Forms of Energy

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Energy Conversion

z Energy cannot be created or destroyed. It can only be converted from one form to another.

z This means that the total energy in a system is always the same, even if the energy has changed to different forms.

Case study 1: A falling ballWhen a ball falls, its height from the ground decreases. So the gravitational potential energy of the ball decreases. At the same time, the ball starts to move faster. So the kinetic energy of the ball increases. When the ball hits the ground and eventually stops moving, there will be friction between the ball and the ground, generating heat and sound energy.

So the energy conversion is:

Gravitational potential energy of the ball Kinetic energy of the ball Heat energy + Sound energy

Case study 2: A torch lightBefore using a torch light, we first need to make sure that the batteries are filled. The batteries provide the chemical potential energy so that when the torch light is switched on, electrical energy can be produced, allowing electricity to flow in the wires. This then lights up the lamp in the torch light.

So the energy conversion is:

Chemical potential energy of the battery Electrical energy in the wires Light energy of the lamp

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Exam Trick

From the case studies, we use two symbols to describe energy conversion: ‘’ and ‘+’. ‘’ is used to represent energy being transferred to another

form or another object. ‘+’ is used to represent different forms of energy produced at the same time

Common mistakes

Example 1Adam released a pendulum bob from Position X as shown in the diagram below. He observed that when the pendulum bob swings to the other end at Position Y, the height of the pendulum bob from the ground is lower compared to position X. Give a reason for this observation.

Energy Conversion

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Common answer students write: Some of the gravitational potential energy of the pendulum bob at X is converted to heat and sound energy.

The answer is incomplete since it does not link to the question. Let’s apply what we learn about linking answers to questions.

Short answer: Gravitational potential energy converted to heat and sound energy.

Highlight key words in answer: Gravitational potential energy converted to heat and sound energy.

Highlight key words in question: He observed that when the pendulum bob swing to the other end at Position Y, the height of the pendulum bob from the ground is lower compared to position A.

Link keywords: converted to heat and sound energy the height of the pendulum bob from the ground is lower there is less gravitational potential energy

converted to heat and sound energy the height of the pendulum bob from the ground is lower there is air resistance during motion

Here’s the correct answer:When the pendulum bob swings from Position X, gravitational potential energy is converted to kinetic energy. Since there’s air resistance, some kinetic energy is converted to heat and sound energy

Energy Conversion

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when moving, causing there to be lesser kinetic energy. When the pendulum bob swings up again, the lesser kinetic energy is converted back to lesser gravitational potential energy. This causes the pendulum bob to have lower height at Position Y.

Example 2A car moves up a slope at constant speed. State the energy changes that take place in the car.

Common answer students write: Chemical potential energy of the fuel Kinetic energy of the car + Gravitational potential energy of the car

The answer is wrong as the car moves up the slope at constant speed. Hence, there is no increase in kinetic energy. The chemical potential energy of the fuel did not convert to the kinetic energy of the car.

Here’s the correct answer: Chemical potential energy of the fuel Gravitational potential energy of the car.

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Example 3The diagram below shows three identical boxes made into two objects, Object A and Object B. Object A is made up of one box while Object B is made of two boxes stacked on top of each other. Both the objects travel at the same speed.

Which object has the greater kinetic energy? Explain your answer.

Common answer students write: Object B. This is because Object B is heavier than Object A.

This is a data-based question. The answer is incomplete as the answer did not use the data. Let’s use what we learn about data-based questions.

Choose the correct option: Object BLink question to general scientific concepts: greater kinetic energy more mass or greater speed.

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Link data to the same concepts: Object B has one more box. Object B and A move at the same speed. Object B has greater mass.

Here’s the correct answer:Object B has greater kinetic energy. This is because Object B has one more box compared to Object A. Since Object B has greater mass while moving at the same speed, Object B has greater kinetic energy.

Example 4The diagram shows two ramps connecting the ground and the back of a truck.

Since Ramp A is longer, a student states that there will be a greater change in gravitational potential energy when he goes up the truck using Ramp A. Do you agree with the student? Explain your answer.

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Common answer students write: Yes. This is because gravitational potential energy depends on the length from the ground. The longer the ramp, the greater the gravitational potential energy.

The answer is wrong because gravitational potential energy depends on the height from the ground, not the length travelled.

Here’s the correct answer: No, I do not agree with the statement. The gravitational potential energy depends on the height from the ground, not the length travelled. Since the height of both ramp is the same, the increase in gravitational potential energy will be the same.

Energy Conversion

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Practice

Question 1An electric kettle is used to boil water. After some time, the water starts to boil and the kettle starts to whistle.

What is the energy conversion involved?

(1) Electrical energy Heat energy Kinetic energy + Sound energy

(2) Electrical energy Heat energy Kinetic energy Sound energy (3) Electrical energy Heat energy Kinetic energy(4) Electrical energy Heat energy Sound energy

Question 2:Which of the following does not have gravitational potential energy?

(1) An aircraft resting on the ground(2) A ball placed on top of a slope (3) A boy climbing up stairs(4) A skydiver jumping off a plane

Question 3:Alicia stretches a rubber band. State the energy conversion in the activity. [1 mark]

Energy Conversion

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Energy Conversion

Question 4:Daniel designs a track for his toy car as shown in the diagram below. The height of the starting point on the track is the same as the height of the highest point on the loop.

Daniel observes that his toy car cannot reach the top of the loop . Give a reason for this.

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Question 1: (1)Question 2: (1)Question 3: (1) Chemical potential energy of Alicia Elastic

potential energy of rubber band

Question 4: When the toy car moves down from the starting point, gravitational potential energy is converted to kinetic energy. Since friction between the car and the track, some kinetic energy is converted to heat and sound energy, causing there to be lesser kinetic energy. When the car moves up the loop, the lesser kinetic energy is converted back to lesser gravitational potential energy. This causes the car to not be able to reach the same height.

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MOCK EXAM I

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Mock Exam I

Booklet AFor each question from 1 to 28, four options are given. One of them is the correct answer. Make your choice (1, 2, 3 or 4) and write your answer in the bracket provided at the end of each question.

1. The diagram below shows two animals: A and B.

Which of the following is correct?

(1) Animal A has fur and wings.(2) Animal A has feathers.(3) Animal B has fur and wings.(4) Animal B has feathers and wings.

2. Which of the following is the similarity between reptiles and mammals?

(1) They have breathing holes.(2) They live only in water.(3) They need oxygen to survive.(4) They have hair.

A B

( )

( )

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Mock Exam I

3. The table below shows the properties of materials A, B, C and D. A tick indicates that the material possesses the property.

(1) Material A (3) Material C(2) Material B (4) Material D

4. The diagram below shows three cells: X, Y and Z.

Which parts are found in all three cells?

(1) cell wall (3) cytoplasm(2) nucleus (4) cell membrane

Material Flexible Strong Transparent WaterproofA ✓ ✓ ✓B ✓ ✓C ✓ ✓D ✓ ✓ ✓

X Y Z

( )

( )

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Mock Exam I

5. The diagram below shows four pictures of an experimental setup used to study the lung capacity of an ex-smoker taken by a student. The setup measures the amount of air he exhales. He stopped smoking since February of this year. The measurements were carried out once every two months after he stops smoking.

The student lost the labels of the pictures and forgot the month when the pictures were taken. Which one of the following shows the correct month of each picture?

February April June August(1) B C A D(2) D C A B(3) B A C D(4) C D B A

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Mock Exam I

6. The food carrying tubes are removed from the outer part of a plant as shown in the diagram below.

Which of the following diagrams correctly shows the appearance of the stem after some time?

7. The diagram below shows an experimental setup used to study the muddy water from a polluted river. A student started the experiment by placing a ball at the bottom of an empty container. Muddy water from a measuring cylinder is slowly added into the container until the student can no longer see the ball. The student then recorded the volume, V of the muddy water used.

(1) (2) (3) (4)

( )

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Mock Exam I

The experiment was repeated using muddy water from different parts of the water, keeping all other variables constant. The results are shown in the diagram below.

Which of the following questions is the student trying to answer from this experiment?

(1) Which region of the river can a coin be observed?(2) Which region of the river has the most amount of mud?(3) Which coin is the hardest to be observed in muddy water?(4) How does the distance between the eye and the coin affect the

observation of the coin? ( )

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Mock Exam I

8. Which of the following describes a behavioural adaptation of an animal?

(1) A camel has long legs so that its body is further away from the hot sand.

(2) A bat has modified limbs to support flight.(3) A lion has sharp teeth to tear the meat of its prey easily.(4) An earthworm burrows underground as the temperature in the

underground is lower.

9. The flowchart below shows how some substances are transported by Systems A, B and C of the human body.

Which of the following shows the correct identities of Systems A and B, and Substances X and Y?

( )

System A System B Substance X Substance Y(1) Circulatory Respiratory Carbon dioxide Oxygen(2) Respiratory Digestive Carbon dioxide Oxygen(3) Digestive Circulatory Oxygen Carbon dioxide(4) Respiratory Circulatory Oxygen Carbon dioxide

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Mock Exam I

10. The diagram below shows a food web connecting different organisms


(1) Organism A is a food consumer.(2) Organisms B and E are carnivores.(3) Organisms D and F are food producers.(4) Organisms C is an omnivore.

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Mock Exam I

Structural adaptation Behavioural adaptation(1) Wait silently to attack

its prey.Shake its rattle to scare off

its predators.(2) Shake its rattle to scare off

its predators.Sense changes in smell using its forked tongue.

(3) Inject poison into its prey with its sharp fangs.

Wait silently to attackits prey.

(4) Sense changes in smell using its forked tongue.

Inject poison into its prey with its sharp fangs.

( )

11. The diagram below shows three organs of a rattlesnake. The rattle makes a sound when the rattlesnake is alarmed.

Which of the following gives the correct types of adaptations?

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Mock Exam I

12. The diagram below shows a water lily plant in a pond.

The leaf floats on the surface of the water and carries out gaseous exchange with the surrounding air. Which of the following is incorrect?

(1) The broad leaf helps with photosynthesis by trapping more light.(2) The thin leaf stalk helps the plant to float by trapping more air.(3) The waxy leaf prevents water from sinking the plant.(4) The stomata on the upper surface of the leaf carries out gaseous

exchange with the surrounding atmosphere. ( )

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Mock Exam I

13. A farmer has two plots of land: A and B. In each plot of land, he grows similar plants under three different conditions as shown in the diagram below.

Which of the following is the possible aim of growing the plants in two different plots of land?

(1) To find out if water is needed for the plant to grow.(2) To study how the amount of water will affect the growth of

the plant.(3) To compare the amount of nutrients in land A and land B.(4) To find out how sunlight affects plant growth.

450ml of water given to the plants daily



( )

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Mock Exam I

14. The diagram below shows how food and gases are transported in our body.

Which of the following correctly represents Systems A, B and C, and Gas D and E?

System A System B System C Gas D Gas E(1) Digestive Circulatory Respiratory Oxygen Carbon dioxide(2) Circulatory Digestive Respiratory Oxygen Carbon dioxide(3) Digestive Respiratory Circulatory Oxygen Carbon dioxide(4) Digestive Circulatory Respiratory Carbon dioxide Oxygen

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15. The diagram below represents the water cycle.

Which letter(s) represent(s) the process where heat is lost to the surroundings?

(1) B only (3) A and D only(2) C only (4) B and C only

16. An experiment was carried out to study how the amount of sugar produced by four different plants depends on the light intensity incident on the plant. The table below summarises the results.

Which plants are suitable for use as indoor plants?

(3) A and B only (3) B and C only(4) A and C only (4) A, B and C

Light intensity (lux) Amount of sugar (mg)Plant A Plant B Plant C

60 31 23 3540 22 12 3020 17 5 18

( )

( )

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Mock Exam I

17. The diagram below shows a jogger and his reflection in the water of a pond.

Another person sees the reflection of the jogger in the water. Which of the following shows the correct pathway of light?

(1) (2)

(3) (4)

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Mock Exam I

18. The classification chart below shows four methods of seed dispersal.

Which of the following organisms does not belong in the declassification chart above?

(1) Papaya tree (2) Bird’s nest fern(3) Rubber tree (4) Dandelion

19. A student carried out an experiment to study how the size of a magnet affects its strength. The experimental setup is shown in the diagram below.

The student moved the paper clip slowly towards the magnet. She recorded the greatest distance, x at which the paper clip can be attracted to the magnet. She carried out the experiment with magnets of four different sizes. The results are shown in the table next page.

( )

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Mock Exam I

Based on the table, which of the following statements is correct?

(1) The strength of a magnet does not depend on its size.(2) The small magnet is stronger than the medium- sized magnet.(3) The huge magnet is the strongest magnet.(4) Only the large magnet can attract paper clips placed at 6 cm away.

20. The lamp connected to the front wheel of a bicycle is powered by a dynamo. A dynamo is a device which converts kinetic energy to electrical energy. Four different students carried out an experiment to investigate how the wheel speed affects the brightness of the lamp. The experimental setup is shown in the diagram below.

Magnet size Small Medium Large HugeDistance x (cm) 8 9 6 3

( )

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Mock Exam I

Each student recorded his or her own results in a table. Only one of them recorded the results correctly. Which of the following tables shows the correct results?

(1)

(2)

(3)

Speed of wheel (Number of turns per minute)

Light intensity (lux)

40 5060 7080 120

100 170



10 2020 4030 5040 30



50 18070 8090 60

110 130

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Mock Exam I

(4)

21. The diagram below shows a tree planted at Locations A and B.

Which of the following is the most likely seed dispersion method of the tree?

(1) By wind (3) By animals(2) By water (4) By splitting



30 19060 14090 90

120 70

( )

( )

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Mock Exam I

22. Three identical switches, six identical bulbs and six identical dry cells are used in the three circuits shown in the diagram below.

Which of the following statements are true?

C. Bulb A does not light up.D. Bulb E is brighter than Bulb C. E. Bulb B and Bulb F are equally bright.F. Bulb B is brighter than Bulb D.

(1) A and B only (3) A and D only(2) A and C only (4) B and C only

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Mock Exam I

23. The diagram below shows the arrangement of five bar magnets with their ends labelled A to J.

Which of the following diagrams show a possible arrangement using two of the bar magnets?

( )

(1) (2)

(3) (4)

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Mock Exam I

24. An experiment was conducted to test the strength of four magnets, A, B, C and D. The shape and relative size of the four magnets are shown in the diagram below.

Each magnet was placed at a certain distance from a pile of identical iron pins. The number of iron pins each magnet attracted was recorded. The results are shown in the table below.

Which of the following statements is incorrect?

(1) Magnet B is the strongest magnet.(2) Magnet D is stronger than Magnet A.(3) Magnet C is stronger than Magnet D.(4) Magnet A is the weakest magnet.

Magnet Distance between magnet and iron pins (cm)

Number of iron pins attracted

A 2 10B 2 15C 4 13D 2 13

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Mock Exam I

( )

25. Which of the following force(s) can act at a distance?

A. Magnetic forceB. Gravitational forceC. Elastic spring forceD. Frictional force

(1) C only (3) A and B only(2) D only (4) A and C only

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Mock Exam I

( )

(1) (2)

(3) (4)

26. Three identical mirrors, a set of connected tubes, a ball and a student are positioned in four different ways. A student looks through a pipe opening to find out if he can see the ball placed at another pipe opening. In which of the following setups can the ball be seen?

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Mock Exam I

27. The diagram below shows a plant cell placed in a liquid containing Substances A and B. Only the nucleus, the cell wall and the cell membrane of the plant cell are shown.

Which of the following statements gives the correct explanation for the observation above?

(1) Substance A moved faster into the cell than Substance B.(2) The cell wall prevented Substance B from entering the cell.(3) The cell membrane prevented Substance B from entering the cell.(4) Substance A blocks Substance B from entering the cell.

( )

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28. This diagram shows a diver about to dive into a diving pool from a diving platform at Position A. After jumping, the diver reaches Positions B, C and D before reaching the water.

Which of the following gives the correct comparison of potential energy and kinetic energy at Positions A and D?

Potential energy Kinetic energy

(1) Higher at A Lower at A(2) Higher at A Lower at D(3) Lower at A Higher at A(4) Lower at D Lower at D

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Booklet BFor questions 29 to 40, write your answers in this booklet.

The number of marks available is shown in brackets [ ] at the end of each question or part question.

29. The diagram below shows two flowers from Plant X.

Flower A Flower B

(a) On the diagram above, draw an arrow to show how cross pollination can take place between Flower A and Flower B. [1]

(b) Based on your drawing, which flower can develop into a fruit? Explain your answer. [1]

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Mock Exam I

(c) Birds help with the reproduction of plant X by dispersing the seeds after eating the fruits. The seeds are small and indigestible. Suggest and explain two benefits for plant X to disperse its seeds through birds. [2]

Benefit 1:

Benefit 2:

30. A butterfly lays some eggs on a piece of leaf.

(a) An adult butterfly lays its eggs only on certain plants. Explain why. [1]

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Mock Exam I

(b) The diagrams below show the adult butterfly feeding on Plant A while its larva feeding on Plant B.

Give a reason why the butterfly and the larvae feed on different plants. [1]

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Mock Exam I

31. Bananas produce ethylene, a gas which causes bananas to ripen faster. To make full use of the ethylene produced by bananas, some farmers wrap bananas in plastic bags. One such wrapping is shown in the diagram below.

(a) Explain how wrapping bananas in a plastic bag can cause the bananas to ripen faster? [1]

(b) Suggest one other advantage for farmers to wrap bananas in a plastic bag. [1]

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(c) A farmer says that the plastic bag used must be transparent, else the bananas will not be able to carry out photosynthesis. Do you agree with the farmer? Explain your answer. [1]

32. The three graphs below show the mass of four different foods, A, B, C and D after passing through different parts of System E of a person. The person ate 100 units of each type of food.

(a) What is system E? [1]

(b) John says that the mouth only chews food into smaller pieces and does not digest food. Do you agree with John? Explain your answer using the graph above. [1]

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(c) Based on the graphs, which food can only be digested in the small intestine? [1]

(d) Describe what happens to the digested food after passing through the small intestine. [1]

(e) What happens to Food A after it passes through the small intestine? [1]

33. A student carried out an experiment to study how the thickness of Material A affects its transparency. The experimental setup is shown in the figure below.

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The results are summarized in the table below.

(a) (i) The student would like to wrap a plastic bottle using Material

A such that no light can enter the bottle. She uses sheets of Material A with thickness of 2 mm each. Based on the table above, what is the minimum number of sheets she should use? [1]

(ii) State one other property of Material A which allows it to be wrapped around the bottle. Explain your answer. [1]

Thickness of Material A (mm) Light intensity recorded (lux)2 144 96 48 0

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The diagram below shows a parking lot sensor. When no car is parked in the lot, the indicator turns green. When a car is parked in the lot, the indicator turns red.

(b) Explain how the parking lot sensor works in indicating whether a car is parked in the lot or not. [2]

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34. The diagram below shows the incomplete setup of Buzz Wire, a common game found in carnivals. The diagram shows a metal loop, a wire maze, two batteries and a light blub. A player must guide the metal loop through the wire maze from Point A to Point B without touching the metal maze. If the metal loop touches the wire maze, the bulb will light up.

(a) Complete the diagram above by drawing wires to connect the components. [1]

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Mock Exam I

(b) Why does the bulb light up if the metal loop touches the wire maze? [1]

When another bulb is added to the circuit, the bulbs become dimmer.

(c) State the type of arrangement of the two light bulbs in the circuit. [1]

(d) After a few minutes, the bulb stops lighting up even when the metal loop touches the wire maze. Suggest a possible reason. [1]

35. The diagram below shows the setup of an experiment. A piece of fabric is rolled up and placed into a funnel covering the mouth of a container. 10 cm3 of water is poured into the funnel. The volume of the water collected in the container is measured and recorded.

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Mock Exam I

Three different types of fabric are used in this experiment: Fabrics A, B and C. The results are shown in the table below.

(a) Which fabric is the most suitable to be used as a towel? Explain your answer. [2]

(b) For a fair comparison between fabrics, state one factor about the fabric that should be kept constant across all three types of fabric. [1]

Fabric A B CVolume of water collected (cm3) 9 5 7

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Mock Exam I

36. The diagram below shows an experimental setup. Two containers are used where one is wrapped in a bubble wrap with trapped air pockets. Other than the wrapping, the containers are identical.

(a) What is the aim of this experiment? [1]

The graph below shows the changes in temperature of the water in Container B.

(b) In the graph above, draw the line which represents the temperature changes of the water in Container A. [1]

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Mock Exam I

(c) A new experiment is conducted. The water in the containers are replaced with equal volumes of water at a starting temperature of 100oC. Which container will have the warmer water? Explain your answer. [1]

In countries with seasonal changes, houses are installed with insulation layers between the inner roofs and the ceilings as shown in the diagram below. There are air pockets in the insulation layers.

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Mock Exam I

(d) Explain how these insulation layers help the people in the house during winter and summer. [2]

Winter:

Summer:

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Mock Exam I

37. In bungee jumping, a person is tied to the end of an elastic cord and jumps from a high position. The cord will stretch downwards and bounce up and down a few times before coming to a rest at a safe distance above the ground.

Since this activity is dangerous, it is important to test the elastic cord before it is used for bungee jumping. The diagram below shows the setup used to test one such elastic cord. The cord is first released from the platform and the minimum distance of the cord from the ground is measured. The experiment is repeated by adding more weights to the end of the elastic cord.

The results are shown in the table below.

Mass of weight (kg) Minimum distance from ground reached (m)

0 1630 1260 890 4

120 0

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Mock Exam I

(a) Based on the table, draw a line graph in the space below. Label the axis. [2]

(b) State the smallest mass which is unsafe for the person to jump using the elastic cord. Explain your answer. [1]

The weights are removed and the elastic cord is laid at rest on the ground as shown in the diagram below.

(c) Draw and label the force acting on the elastic cord in the diagram above. [1]

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38. A tourist was in Europe during a winter holiday. She felt cold and went into the tour bus since the bus had a heater installed. After some time, the tour bus departed to another town. She noticed that mist was formed on the inner surface of the window in the bus.

(a) Explain how the mist was formed on the inner surface of the window. [1]

(b) The tourist drew a smiley emoji on the wet window with her finger and fell asleep. After she woke up, she noticed that the emoji was gone even though nobody wiped it away. Explain how it happened.[1]

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39. The table below shows the melting and boiling points of three substances, A, B and C.

Lisa works in a laboratory of room temperature 30℃. She stored 2000 cm3 of a substance in a container with a volume of 1000 cm3.

(a) Based on the table, which substance did she store? Explain your answer. [1]

Jean had a basket made of wire mesh as shown in the diagram below.

Substance Melting point (℃) Boiling point (℃)A 10 110B 140 290C 0 10

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(b) Can Jean store Substances A and B into the basket shown on the right? Explain your answer. [2]

40. The diagram below shows a skater standing on his skateboard at the top of Ramp A.

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(a) The skater skates down Ramp A from Point X. Fill in the blanks below to show the energy conversion as the skater moves down from Point X. [1]

_______________energy of the skater is converted into _______________ energy of the skater and _______________ energy of the surroundings.

(b) When the skater skates down from Point X, the skater stops at Point Y. Give a reason for this. [1]

(c) When the skater skates down Ramp B from Point Z, will the skater stop at Point Y? Explain your answer. [2]

ANSWERS - MOCK EXAM 1

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Mock Exam I - Answers

Booklet A

Q1: 4 Q2: 3 Q3: 4 Q4: 4 Q5: 3 Q6: 4 Q7: 2

Q8: 4 Q9: 4 Q10: 4 Q11: 3 Q12: 2 Q13: 3 Q14: 1

Q15: 1 Q16: 2 Q17: 3 Q18: 2 Q19: 1 Q20: 1 Q21: 2

Q22: 1 Q23: 2 Q24: 1 Q25: 3 Q26: 4 Q27: 3 Q28: 1

Booklet B

Q29 (a)

(b) Flower B can develop into a fruit. Flower B receives pollen grains on its stigma from the anther of Flower A. The pollen grains travel to the ovary through the style. Fertilisation occurs after the pollen grains fuse with the ovules, resulting in Flower B developing into a fruit.

(c) Benefit 1: The seeds will be passed out as waste materials from the bird. The waste materials will enrich the soil the seeds land on. This promotes the growth of young plants.

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Q30 (a) The larva eats only certain leaves.(b) So that the larva does not have to compete with the adult

butterfly for food.

Q31 (a) The plastic bag traps the ethylene produced by the bananas. Since the bananas are always surrounded by ethylene, the bananas will ripen faster.

(b) Animals will not be able to feed on the bananas.(c) No, I do not agree with the farmer. Fruits do not carry

out photosynthesis. It is the leaves which carry out photosynthesis.

Q32 (a) Digestive system(b) I do not agree with John. If the mouth does not digest food,

the mass of C and D after passing through the mouth should still be 100 units each.

(c) Food B(d) Digested food is absorbed into the bloodstream.(e) The undigested Food A moves into the rectum.

Q33 (a) (i) 4 sheets

(ii) Flexibility. The material has to be flexible so that it can wrap the whole bottle.

(b) Light from the light source cannot pass through a car as cars are opaque. So when a car is parked in the lot, the light sensor does not detect any light and the indicator will turn red. When no car is parked in the lot, the light sensor detects light from the light source and the indicator will turn green.

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Q34 (a)

(b) When the metal loop touches the wire maze, the circuit is closed. Hence, electricity can flow through the bulb and the bulb lights up.

(c) Series arrangement

(d) The wires were loosely connected to the light bulb.

Q35 (a) Fabric B. When Fabric B is used in the funnel, the least volume of water was collected in the container. This shows that Fabric B absorbs the most amount of water. When a person uses Fabric B as the towel when he is wet, he can dry himself faster.

(b) The thickness of the fabric

Q36 (a) To find out if the presence of the bubble wrap affects the temperature of the water in the container.

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Q36 (b)

(c) Container A. The rate of heat loss from the water in container A to the surroundings is slower since there are trapped air pockets in the bubble wrap. Air is a poor conductor of heat.

(d) Winter: The heat from inside the house will be transferred slower to the colder surroundings outside the house. This keeps the house warm.Summer: The heat from the warmer surroundings outside the house will be transferred slower to the house. This keeps the house cool.

Q37 (a)

(b) The smallest mass is 120 kg. The person would reach a minimum distance of 0 m from the ground. Hence, he will hit the ground and suffer head injury.

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Q38 (a) Warmer water vapour in the air inside the tour bus touched the cooler surface of the window. The water vapour lost heat to the window and condensed to form water droplets.

(b) The water droplets gained heat from the warmer air inside the bus and evaporated.

Q39 (a) C. The boiling point of C is above 30℃ so C is a gas at room temperature. Hence, it has no definite volume and can be stored in a container of lower capacity.

(b) A cannot be stored but B can be stored. B is a solid at room temperature. B has a definite shape and will not escape the basket through the holes. A is a liquid at room temperature. It does not have a definite shape and can escape the basket through the holes.

Q40 (a) Gravitational potential, kinetic, heat(b) There is friction between the wheels of the skateboard and

the ramp. Friction opposes the motion of the skater and generates heat. So all the kinetic energy of the skater is converted to heat and sound energy when the skater reaches Point Y.

(c) No. Point Z is higher than Point X. So the skater will store more gravitational potential energy at Point Z which is converted to more kinetic energy. This allows the skater to skate beyond Point Y.

Q37 (c)

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Booklet AFor each question from 1 to 28, four options are given. One of them is the correct answer. Make your choice (1, 2, 3 or 4) and write your answer in the bracket provided at the end of each question.

1. Which component of an animal cell controls movement of substances in and out of the cell?

(1) Nucleus (3) Cell wall(2) Cell membrane (4) Cytoplasm

2. Which of the following is an example of a fungus?

(1) Fiddlehead fern (3) Palm tree(2) Yeast (4) Kelp

3. Godwin wanted to make some colourful roses for his girlfriend’s birthday. He placed white roses into jars containing water dyed with different colours. A few days later, the roses turned colourful. Which part of the plant is responsible for taking up the colours?

(1) Roots (3) Flowers(2) Leaves (4) Fruits

( )

( )

( )

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4. Organism G lives in a cave with no light source. What can organism G do to increase its chance to mate and reproduce?

(1) It could reveal its colourful body covering to attract its mate.(2) It could dance to attract its mate.(3) It could fight other males of organism G to attract its mate.(4) It could glow to attract its mate.

5. Study the food chain below.

Algae → Prawn → Fish → Shark

A new organism, Organism X, was introduced into the ocean, and affects the population of fish as seen below.

Which one of the following graphs shows the likely changes to the populations of the other organisms when organism X has been introduced?

( )

( )

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( )

6. Organism A senses food with one of its organs. Organism A leaves a trail for other members of organism A to follow. Together, the group carries the food back to their nest. Halfway while carrying the food, a tree collapses and crushes the group. New members of organism A arrive and continue to carry the food.

Based on the scenario above, what can you conclude about the way organism A has adapted?

(1) Organism A works in a highly cooperative manner to obtain food.(2) Organism A works alone to obtain food.(3) Organism A works with another different organism to obtain food.(4) Organism A utilises complex strategies to hunt for food.

7. Noelle discovered an organism which has the following characteristics.

z It has poor eyesight. z It has long curved claws with short limbs. z It has a sensitive nose to sense its surroundings.

Which habitat would the organism most likely be living in?

(1) Pond (3) Desert(2) Arctic 4) Underground

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8. The diagram below shows two mango trees, X and Y, in a garden. Both trees were planted at the same time and separated such that they cannot cross-pollinate.

After several months, it was observed that Tree X had many mango fruits, but Tree Y had none. Which of the following reason(s) below explain(s) this observation?

A. Tree Y has a disease that makes it unable to grow flowers.B. The flowers on Tree X have undergone self-pollination.C. The flowers on Tree Y were not as large as the ones on X.D. Tree Y attracts more pollinators than Tree X

(1) C only (3) A and B only(2) B and C only (4) B, C and D only

( )

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9. In general, which of the following is only present in plant cells and not animal cells?

(1) Nucleus (3) Chloroplast(2) Cell membrane (4) Cytoplasm

10. Ben saw an ostrich in the zoo and wrote down some notes about it. Which of the following statements about the ostrich is incorrect?

(1) It has a beak.(2) It eats plants and roots.(3) Its body is covered with feathers(4) It has wings and webbed feet to help it swim.

11. Cyrus performed an experiment to investigate how plants make and store starch. Which of the following experimental setups will lead to a plant that produces the greatest amount of starch?

(1) Plant is placed in a box with all leaves cut off.(2) Plant is placed under light with all leaves cut off.(3) Plant is placed in a box with all flowers cut off(4) Plant is placed under light with all flowers cut off

( )

( )

( )

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12. Amber performed a science experiment to see what makes seeds grow. She has four different jars with different conditions. Which jar will lead to growth of a plant?

(1) Seed in open jar on a cotton wool soaked in oil, placed in a fridge(2) Seed in sealed jar on a cotton wool soaked in water, placed in

a fridge(3) Seed in open jar on a cotton wool soaked in oil, placed near

a window(4) Seed in open jar on a cotton wool soaked in water, placed near

a window 13. The diagram below shows the direction of blood flow in the human

body.

Which two arrows in this diagram are not correct?

(1) U and V (2) U and Z(3) W and X(4) Y and Z

( )

( )

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14. Heidi saw that cactus can survive well in a desert. Heidi drew a labelled diagram of a cactus as shown in the diagram below.

Heidi listed down some adaptations which she believed helps the cactus to survive.

A. It has thin, spiky leaves to reduce water loss.B. It has thick, waxy skin to trap more sunlight. C. It has large, fleshy stems to store water.D. It has long shallow roots to absorb water from a wide area.

Which statements correctly describe the adaptations of cactus to survive in a desert?

(1) A and B only (3) A, C and D only(2) C and D only (4) A, B, C and D

( )

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15. Which of the following objects is wrongly matched to the material it is made of?

16. Susan sets up four circuits as shown in the diagram below. The batteries, bulbs and switches are all working properly.

Which bulb will be the brightest?

(1) A (3) C(2) B (4) D

( )

Object Material(1) Paper Wood(2) Eraser Rubber(3) Wires Clay(4) Needle Metal

( )

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17. Amber conducted an experiment using the setup shown in the diagram below. Some iron ball bearings are fixed to the bottom of box Q. She placed box Q and its ball bearings on the ramp.

She observed that Box Q stopped at point X.

From her observation, why do you think box Q stopped at point X when placed on the iron ball bearings?

(1) The amount of gravitational force is greater at point X.(2) There is no more gravitational potential energy at point X.(3) The ball bearing was attracted by object K which was a magnet.(4) Large frictional force was acting on the ball bearings, causing box Q

to slow down. ( )

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18. Razor lifts weights in his room to exercise his arms. One day, he decides to lift weights in the swimming pool instead. He finds that he is able to lift more weights in the swimming pool compared to in his room.

Why is Razor able to lift more weights in the swimming pool than in his room?

(1) Razor started off more energetic in the swimming pool than in his room.

(2) The water in the pool exerts an upward pushing force on the weights.

(3) The weights have less mass in the swimming pool.(4) The gravitational force acting on the weights is lesser in the

swimming pool. ( )

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19. Fried ice-cream is a dessert where the cold ice-cream being served is surrounded by a warm, crispy shell. The ice-cream does not melt during the frying process even though it is dipped into hot, boiling oil. The diagram below shows one such fried ice-cream.

A student made three statements to explain why the ice-cream does not melt.

A. The shell is a poor conductor of heat, slowing down the heat gain by the ice-cream from the hot oil.

B. The thin shell allows the shell to be fried quickly, reducing the amount of time spent in hot oil.

C. The ice-cream does in fact melt but evaporates before being served to the customer.

(1) A and B only (3) B and C only(2) A and C only (4) A, B and C

( )

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( )

20. Bennett had a fidget spinner. He took it apart and saw the ball bearings in it as shown in the diagram below.

He wanted to find out how the number of ball bearings would affect the time taken for the fidget spinner to come to a complete stop. Which variable is not necessary for Bennett to take note of during the experiment?

(1) The amount of force applied to the idget spinner.(2) The number of ball bearings in the fidget spinner.(3) The number of turns the fidget spinner takes before it comes to a

complete stop.(4) The time taken for the fidget spinner to come to a complete stop.

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21. A teacher shows her students a chart of four water processes classified as shown below. Students are asked to find the suitable words to replace ‘Blank A’ and ‘Blank B’.

Which of the following shows the correct words to replace ‘Blank A’ and ‘Blank B’ respectively?

Blank A Blank B(1) Constant Constant(2) Constant Decreases(3) Decreases Constant(4) Decreases Decreases

( )

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22. The diagram below shows an experimental setup used to study the amount of light passing through Material A.

The graph below shows the results obtained.

Which of the following is most likely to be Variable B?

(1) Thickness of Material A(2) Number of bulbs connected in series(3) Number of batteries connected in series(4) Distance between light bulb and Material A

( )

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23. __________ is a material that can be stretched and returned to its original state.

(1) Glass (3) Rubber(2) Wood (4) Plastic

24. Four containers are filled with equal volumes of water at different starting temperatures and different locations. The humidity of each location is different. Which water will experience the highest rate of evaporation?

( )

( )

Humidity (%) Starting temperature (℃)(1) 75 20(2) 75 70(3) 10 20(4) 10 70

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25. Lisa opened the cover of her stapler to refill the stapler. She noticed that the spring in the stapler was compressed. The spring would slowly move back to its original length when she used the stapler to staple papers.

Which of the following statements correctly describes a force on the staples as Lisa stapled the papers using the stapler?

(1) Gravitational force acted on the stapler to pull down each staple.(2) Pushing force exerted by the spring on the staples moves the

staple forward.(3) Magnetic force of the worksheet pulled the staple towards

the worksheet.(4) The pulling force exerted by the staples on each other as the spring

is being compressed.

( )

CoverStaples are

inserted here

Spring

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26. Amelia carried out an experiment with four magnets of different length. Each magnet is held at a fixed distance from a pile of thumbtacks as shown in the diagram below.

The number of thumbtacks attracted by each magnet are recorded in the table below.

Which statements can Amelia infer from this experiment?

D. Magnetic force can act at a distance.E. The strength of a magnet can be reduced by dropping it.F. The strength of a magnet does not depend on its length.G. When left on its own, a magnet will align itself along the North-

South direction of the earth.

(1) A and B only (3) B and C only(2) A and C only (4) A, B, C and D

( )

Length of magnet (cm) 10 13 16 19Number of thumbtacks

attracted4 3 6 7

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27. Barbara bought a new magnetic duster for the whiteboard in her classroom. There is a magnet inside the magnetic duster and there is a piece of iron plate inside the whiteboard. She placed the duster on the surface of the whiteboard, but the duster slid down the whiteboard as shown in the diagram below.

Which of the following statements explains Barbara’s observations?

(1) The magnetic force of the magnet is less than the gravitational force of the duster.

(2) The friction acting on the duster is greater than the gravitational force of the duster.

(3) The magnetic force of the magnet is greater than the gravitational force of the duster.

(4) The sum of the friction acting on the duster and the magnetic force of the magnet is less than the gravitational force of the duster.

( )

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28. The arrows A, B and C show the direction of light in the diagram below.

When the lamp in the room is switched on, Zhongli is able to see both the lamp and his friend, Venti. Which arrow(s) show(s) how Zhongli is able to see the lamp and Venti?

( )

Lamp Venti(1) C A then B(2) A B then C(3) A then B C(4) C then B A

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Booklet BFor questions 29 to 40, write your answers in this booklet.

The number of marks available is shown in brackets [ ] at the end of each question or part question.

29. Plant A floats on the surface of a pond as shown in the diagram below. When water lands on the leaf, the water forms round droplets and rolls off the leaf.

(a) What is the property of leaf X that enables water droplets to be formed? [1]

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(b) Describe how the above property helps the plant to grow well in a pond. [1]

30. The picture below shows a sloth found in a tropical rainforest. Sloths are usually found hanging upside down at treetops.

(a) Green algae often grow on the fur of sloth. How does the green algae help the sloth in avoiding being seen by its predators? [1]

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Mock Exam II

(b) Study the claws of the sloth in the picture carefully. Suggest how the claws of the sloths are adapted to living on trees. [2]

(c) The furs of the sloths hang upside down. Suggest how this adaptation allows sloths to keep themselves dry during rain. [1]

31. A lack of oxygen can lead to damage in many organs, including the heart itself. This causes heart attacks, resulting in a faster or slower heart rate.

(a) Explain why a blockage in blood vessels can cause a change in heart rate during a heart attack. [2]

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The blockage in vessels can be due to fats building up inside the blood vessel. Another source of blockage is due to clots forming when a patient does not move a lot.

(b) List two things you can do to reduce the chance of having a heart attack. [2]

32. Candice sliced four equal sizes of meat from a chicken. She placed the slices in four different test tubes and stored them under different conditions as shown in the diagram below.

(a) State the observations of the raw meat in Test Tube A after one week. Explain your answer. [2]

Raw meat placed in

a room

Meat heatedto removeall water

Raw meatsealed with

rubber

Raw meat stored in

the freezer

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(b) Was decomposition observed in Test Tubes B, C and D? [1]

(c) What can be concluded from this experiment? [1]

33. Michael dropped a seed from different heights in front of a fan. He wants to find out how the distance travelled by the seed depends on the starting height. The results are shown in the table below.

(a) Based on the table, suggest why the seed tends to be found on tall trees. [1]

(b) For each starting height, Michael reused the same seed. Give two variables which are kept constant when the same seed is used. [2]

Starting height (cm) 110 90 70 50Distance travelled (cm) 45 39 26 10

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(c) Michael found a few more seeds from the same tree. The seeds have different mass. He wanted to carry out another experiment to find out how the mass affects the distance travelled by the seed. Suggest two variables which must be kept constant during this new experiment. [2]

34. The diagram below shows the food web between different organisms.

(a) Based on the food web, which organism is a food producer? [1]

(b) State whether Organism C is a herbivore, carnivore or omnivore. Explain your answer. [1]

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(c) Lashley made the following statement:

“Even though Organism E does not consume Organism B directly for food, it still depends on Organism B indirectly. Hence, all the energy contained in Organism B will eventually be passed on to Organism E.”

Do you agree with the statement? Explain your answer. [2]

(d) Organism F feeds on all five Organisms A to E after they are dead. What is Organism F and why are they important to the environment? [1]

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35. The diagram below shows an experimental setup to study the time taken to boil water using different burners. The two pots are identical with the same amount of water at the start.

(a) Suggest a material used to make the handle. Explain your answer. [1]

(b) Based on the diagram above, which burner uses less energy to boil the water? Explain your answer. [2]

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The experiment is now repeated with water in both pots boiled using Burner A. One of the pots is covered with a lid as shown in the diagram below.

(c) Which pot will boil first? Explain your answer. [2]

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36. The diagram below shows a plastic suction cup with a hook. It is placed on a glass window so that it can be used to hang objects on windows.

When the suction cup is pressed hard against the window, the air in the cup escapes, leaving behind very little air inside the cup.

(a) Why is the suction cup able to stick to the glass window without falling down? [2]

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(b) Siti does not press the suction cup hard against the window. She finds that the suction cup is not able to stick to the window and keeps falling. Give a reason behind this behaviour. [1]

(c) Siti claims that a bigger suction cup which is pressed hard against the window will allow her to hang heavier objects on the hook without falling. Do you agree with her? Explain your answer. [1]

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37. The diagram below shows an alarm system. The warning lamp of the system lights up when the room becomes too hot. The glass tube consists of liquid mercury and a metal conductor. At room temperature, the liquid mercury and the metal conductor are not touching each other.

(a) Describe how the alarm system works. [2]

(b) Suggest why the metal conductor cannot be replaced by a plastic in the glass tube. [1]

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(c) The alarm system ended up not being very useful as the warning lamp is not bright enough to be observed by the people in the room. Suggest one way to modify the circuit so that the lamp will be brighter. [1]

38. A steel nail can be magnetised by stroking it using a bar magnet as shown in the diagram below.

(a) Describe one way to test if the magnet has been magnetised. [1]

(b) State one way to make a magnet loses its magnetic force. [1]

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39. Daniel carried out an experiment to test whether food contains chemical potential energy. He poured some water into a container and placed a piece of burning food under the container. He measured the temperature of the water over time using a thermometer. The setup is shown in the diagram below.

The results are shown in the graph below.

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(a) Fill in the blanks in the sentence below with the correct form of energy. [1]

__________ energy in food → __________ energy in food → __________ in water

(b) Based on the results of the experiment, state one possible use of chemical potential energy in daily life. [1]

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40. Shawn conducted an experiment by placing ice of the same volume into two identical cups filled with equal amounts of water. Cup A is filled with one big block of ice while Cup B is filled with ice chunks as shown in the diagram below.

(a) After one minute, Shawn measures the temperature of the water in each cup using a thermometer. Water in which cup will have a lower temperature? Explain your answer. [2]

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Mock Exam II

Shawn repeated the experiment with one metal cup and one plastic cup. The two cups have the same size. At the start, both cups are filled with equal amounts of water and have one block of ice each as shown in the diagram below. The two blocks of ice are identical.

(b) After one minute, Shawn measures the temperature of the water in each cup using a thermometer. Water in which cup will have a lower temperature? Explain your answer. [2]

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ANSWERS - MOCK EXAM II

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Mock Exam II - Answers

Booklet A

Q1: 2 Q2: 2 Q3: 1 Q4: 4 Q5: 1 Q6: 1 Q7: 4

Q8: 3 Q9: 3 Q10: 4 Q11: 4 Q12: 4 Q13: 4 Q14: 3

Q15: 3 Q16: 2 Q17: 3 Q18: 2 Q19: 1 Q20: 3 Q21: 2

Q22: 3 Q23: 3 Q24: 4 Q25: 2 Q26: 2 Q27: 4 Q28: 1

Booklet B

Q29 (a) Waterproof(b) Since the leaf of Plant A is waterproof, it will not be weighed

down by absorbing water. Hence, it is able to float on the surface of water and traps more sunlight to carry out photosynthesis.

Q30 (a) The colour of the green algae camouflages the sloth among the green leaves of the trees.

(b) Sloths have large, curved claws. This allows them to hang on branches very easily when they eat and sleep.

(c) When rainwater lands on a sloth hanging upside down, the rainwater will flow away from its body.

Q31 (a) The blockage of vessels causes lack of oxygen since oxygen cannot circulate properly. The lack of oxygen damages the heart. The damaged heart cannot pump blood properly, causing the heart rate to change.

(b) Eating a balanced diet and exercise

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Q32 (a) The meat felt mushy and gave a foul smell. The meat has been broken down into simpler substances by decomposers.

(b) Decomposition is observed in C but not B and D(c) Water and warmth are needed for decomposition to

take place.

Q33 (a) If the seed is dropped from a higher ground, it can travel further. Hence, the seed can be dispersed further away from the parent tree if dropped from a tall tree.

(b) The mass of the seed, the size of the seed(c) The height from which the seed is dropped, the speed of

the fan

Q34 (a) Organism B(b) Organism C is an omnivore. Organism C consumes Organism

B, which is a plant. Organism C also consumes Organisms A and D, which are animals.

(c) No. Not all energy from Organism B will end up in Organism E. Some of the energy will be used up by Organisms A, C and D for life processes such as growth and respiration.

(d) Organism F is a decomposer. During decomposition, Organism F breaks down dead organisms into simpler substances. This is important as the simpler substances are returned to the soil as nutrients for plants.

Q35 (a) Plastic. Plastic is a poor conductor of heat. When a person touches the handle, the plastic slows down heat gain by the hand from the hot water, making it safer for the person to touch the handle.

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Q36 (a) The air from the atmosphere exerts an inward force on the suction cup, pressing it against the window. Since there is very little air inside the cup, the outward force due to the air pushing the cup away from the window is very small. Hence, the cup is able to stick to the wall.

(b) When air enters the suction cup, the outward force from the air pushing the cup away from the window becomes stronger. The suction cup is pressed less hard against the surface. The friction between the cup and the window decreases. The downward gravitational force is now larger, causing it to slide down.

(c) The bigger suction cup will have a greater exposed surface area to the atmosphere. Hence, the inward force from the atmospheric air will be stronger, pressing the suction cup harder against the window.

Q37 (a) When the room becomes hotter, the liquid mercury will gain heat and expands. It will rise and touch the metal conductor. The circuit is closed and electricity flow. Hence, the warning lamp lights up.

(b) If plastic is used, when the liquid mercury touches the plastic after expanding, no electricity can flow since plastic is an insulator of electricity.

(c) Add more batteries in series.

Q35 (b) Burner A uses less energy to boil. More heat from Burner B is transferred to the surrounding air instead of the pot since the flame is bigger than the base of the pot.

(c) The water in Pot P will boil first. The lid of Pot P prevents hot water vapour from escaping. Less heat energy is lost from the pot, allowing the water to boil faster.

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Q38 (a) Place the magnet near some paper clips. If the magnet attracts the paper clips, the magnet is magnetised.

(b) Hit the magnet/Heat the magnet.

Q39 (a) Chemical potential, heat, heat(b) Chemical potential energy of food can be used to boil water

when the food is burnt.

Q40 (a) The water in cup B will have a lower temperature. The ice chunks have larger exposed surface area than the ice block. Water will lose heat faster to the ice chunks, resulting in lower temperature.

(b) The water in the plastic cup will have a lower temperature. When water cools down, the surrounding air becomes hotter than the water. Hence, water will gain heat from the surrounding air. Since plastic is a poor conductor of heat, it will slow down the heat gain by the water from the surrounding air. Water will then cool down faster.

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