PSLE Science: Model-Answer Keywords (Say This, Not That)
Score the open-ended section by writing the exact words the PSLE marker is looking for. This deck pairs a real exam cue with the scoring model-answer phrase for every high-frequency 2026 topic — heat & energy transfer, plants & photosynthesis, the human digestive system, forces, electrical circuits, and matter & the water cycle. Each card replaces vague phrasing ("the water disappeared") with the precise, mark-winning version ("the water gained heat and evaporated into water vapour"), plus command-word and answering-framework cards so pupils write what each question actually asks for. Built for a 10-minute daily review with spaced repetition in the run-up to the September paper.
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Cards in this deck
#1
Q:Why did the ice cube get smaller after some time on the table?
- A:The ice gained heat from the surroundings and melted, changing state from solid to liquid.
#2
Q:Explain why the metal spoon left in hot soup becomes hot.
- A:Metal is a good conductor of heat, so heat is transferred from the hot soup to the cooler spoon and the spoon gains heat.
#3
Q:Why is the handle of a frying pan made of plastic?
- A:Plastic is a poor conductor of heat (an insulator), so little heat is transferred to the hand and the handle stays cool to hold.
#4
Q:A cold drink was left out. Why did water droplets form on the outside of the glass?
- A:Water vapour in the surrounding air lost heat to the cold glass and condensed into water droplets on the glass.
#5
Q:Why did the temperature of the hot water drop after a while?
- A:The hot water lost heat to the cooler surroundings until both reached the same temperature.
#6
Q:When does heat stop flowing between two objects?
- A:Heat stops flowing when both objects reach the same temperature.
#7
Q:In which direction does heat always flow?
- A:Heat always flows from a hotter region/object to a colder region/object.
#8
Q:Why does the gap in a metal structure get smaller on a hot day?
- A:The metal gains heat and expands, so it takes up more space and the gap becomes smaller.
#9
Q:Why is a small gap left between railway tracks?
- A:On a hot day the metal tracks gain heat and expand; the gap gives room for expansion so the tracks do not bend.
#10
Q:Why did the liquid in the thermometer rise when placed in warm water?
- A:The liquid gained heat and expanded, so it took up more space and rose up the tube.
#11
Q:Explain why food in a vacuum flask stays warm for a long time.
- A:The flask is made of poor conductors of heat, which reduce the heat lost from the food to the surroundings.
#12
Q:Why does wearing a sweater keep you warm?
- A:A sweater is a poor conductor of heat, so it reduces the heat lost from the body to the cooler surroundings.
#13
Q:Why does a puddle of water dry up on a sunny day?
- A:The water gained heat from the surroundings and evaporated, changing into water vapour.
#14
Q:Why do wet clothes dry faster on a hot, windy day?
- A:The water gains heat faster and the moving air removes the water vapour, so evaporation is faster and the clothes dry more quickly.
#15
Q:What is the difference between heat and temperature?
- A:Heat is a form of energy that flows from a hotter to a colder object, while temperature is a measure of how hot or cold an object is.
#16
Q:Why does a metal chair feel colder than a wooden chair at the same temperature?
- A:Metal is a better conductor of heat, so it draws heat away from the hand faster, making it feel colder.
#17
Q:What is the correct way to say heat travels from A to B?
- A:Heat is transferred (flows) from the hotter object to the colder object — never say heat 'moves' or 'cold flows'.
#18
Q:Name the energy conversion when a torch is switched on.
- A:Electrical energy from the battery is converted into light energy and heat energy.
#19
Q:Describe the energy conversion when a moving car brakes to a stop.
- A:Kinetic energy is converted into heat energy due to friction between the brakes and the wheels.
#20
Q:What energy conversion takes place during photosynthesis?
- A:Light energy from the Sun is converted into chemical (food) energy stored in the plant.
#21
Q:What energy is stored in a stretched rubber band?
- A:It has potential energy (elastic potential energy) stored because it is stretched.
#22
Q:What energy does a ball held high above the ground have?
- A:It has potential energy (gravitational potential energy) due to its raised position.
#23
Q:Describe the energy conversion as the raised ball falls to the ground.
- A:Potential energy is converted into kinetic energy as the ball falls.
#24
Q:What is the main source of energy for the water cycle and almost all living things?
- A:The Sun.
#25
Q:Why do green plants need sunlight?
- A:Plants need light energy to make food (glucose) by photosynthesis.
#26
Q:State what a plant takes in and gives out during photosynthesis.
- A:It takes in carbon dioxide and water and, using light trapped by chlorophyll, makes food (glucose) and gives out oxygen.
#27
Q:Why are leaves green?
- A:Leaves contain chlorophyll, a green substance that traps light energy for photosynthesis.
#28
Q:Why did the plant kept in the dark turn yellow and die?
- A:Without light it could not carry out photosynthesis to make food, so it had no energy to survive.
#29
Q:Why does a plant with most of its leaves removed grow poorly?
- A:Leaves are where photosynthesis takes place, so with fewer leaves the plant cannot make enough food to grow well.
#30
Q:What is transpiration?
- A:Transpiration is the loss of water from a plant as water vapour, mainly through the tiny openings (stomata) in the leaves.
#31
Q:Why did the plant wilt on a hot day?
- A:The plant lost water through transpiration faster than the roots could absorb it, so it wilted.
#32
Q:Why did water droplets form inside a plastic bag tied over a leafy plant?
- A:Water vapour lost by the plant through transpiration condensed into water droplets on the cooler plastic.
#33
Q:State two functions of the roots.
- A:The roots absorb water and mineral salts from the soil and anchor the plant firmly in the ground.
#34
Q:What is the function of the stem?
- A:The stem holds up the plant and transports water and food between the roots and the leaves.
#35
Q:Why did a celery stalk placed in coloured water turn that colour?
- A:The coloured water was transported up the stem from the roots, showing how water travels up the plant.
#36
Q:Why are most leaves broad and flat?
- A:A broad, flat shape gives a large surface area to absorb more light for photosynthesis.
#37
Q:How do green plants help keep oxygen in the air?
- A:During photosynthesis, plants take in carbon dioxide and give out oxygen.
#38
Q:Why is photosynthesis important to animals?
- A:It produces food and oxygen, which animals depend on to survive.
#39
Q:What is digestion?
- A:Digestion is the breaking down of food into smaller, simpler substances that can be absorbed by the body.
#40
Q:Why must food be digested?
- A:Food must be broken down into simpler substances so it can be absorbed into the bloodstream and used by the body.
#41
Q:Where does digestion begin and how?
- A:Digestion begins in the mouth, where the teeth break food into smaller pieces and saliva begins to digest it.
#42
Q:What is the function of the teeth in digestion?
- A:The teeth break food into smaller pieces, increasing the surface area for digestion.
#43
Q:What is the role of saliva?
- A:Saliva moistens the food and contains substances that begin to digest it.
#44
Q:What does the gullet (oesophagus) do?
- A:The gullet pushes the food down from the mouth to the stomach.
#45
Q:What happens to food in the stomach?
- A:The stomach churns the food and produces digestive juices that break it down further.
#46
Q:Where is most digested food absorbed?
- A:Most digested food is absorbed into the bloodstream in the small intestine.
#47
Q:Why does the small intestine have long, folded inner walls?
- A:The folds give a large surface area to absorb digested food quickly and efficiently.
#48
Q:What is the function of the large intestine?
- A:It absorbs water from the undigested food, and the remaining waste is removed from the body.
#49
Q:What is absorption?
- A:Absorption is the taking in of digested food substances into the bloodstream.
#50
Q:Why can't undigested food be used by the body?
- A:Undigested food is too large to be absorbed into the bloodstream, so it is removed as waste.
#51
Q:How is digested food carried to all parts of the body?
- A:Digested food is absorbed into the blood and transported by the circulatory system to all parts of the body.
#52
Q:List, in order, the parts food passes through during digestion.
- A:Mouth, gullet (oesophagus), stomach, small intestine, large intestine.
#53
Q:Name three effects a force can have on an object.
- A:A force can change an object's shape, its speed (start, stop, speed up or slow down), or its direction of movement.
#54
Q:Why does a ball rolling along the ground slow down and stop?
- A:Frictional force acts in the opposite direction to its motion, slowing the ball down until it stops.
#55
Q:In which direction does friction act on a moving object?
- A:Friction always acts in the opposite direction to the motion of the object.
#56
Q:Give two effects of friction.
- A:Friction slows down moving objects, produces heat, and causes wear and tear.
#57
Q:State two ways to reduce friction.
- A:Make the surfaces smoother, add a lubricant such as oil, or use rollers/wheels.
#58
Q:Why are vehicle tyres made with grooves?
- A:The grooves increase friction between the tyres and the road, giving better grip so the vehicle does not skid.
#59
Q:Why does a dropped object always fall to the ground?
- A:Gravitational force pulls the object downwards towards the centre of the Earth.
#60
Q:What gives an object its weight?
- A:Weight is the amount of gravitational force acting on the object.
#61
Q:What is elastic spring force?
- A:It is the push or pull produced by a stretched or compressed spring or elastic object as it returns to its original shape.
#62
Q:Why does a stretched rubber band fly off when released?
- A:The elastic spring force in the stretched band pushes it back to its original shape, sending it off.
#63
Q:Why can a magnet attract a paper clip without touching it?
- A:Magnetic force can act over a distance (without contact) on magnetic materials such as iron and steel.
#64
Q:Explain why two magnets pushed away from each other.
- A:The like poles of the magnets (e.g. north and north) were brought together, and like poles repel each other.
#65
Q:Why does a parachute slow down a skydiver's fall?
- A:Its large surface area increases air resistance (a kind of friction), which acts upwards against the fall and slows it down.
#66
Q:Why does a feather fall more slowly than a stone?
- A:The feather experiences more air resistance compared with its weight, so it falls more slowly.
#67
Q:Why is friction useful when we walk?
- A:Friction between our shoes and the floor gives us grip so we do not slip.
#68
Q:Why do your hands feel warm when you rub them together?
- A:Friction between the hands produces heat, which warms them up.
#69
Q:State one way to increase friction between two surfaces.
- A:Make the surfaces rougher, or press them together more firmly.
#70
Q:What must be true for a bulb to light up in a circuit?
- A:The circuit must be closed (complete) so that electric current can flow through the bulb.
#71
Q:Why did the bulb not light up?
- A:The circuit was open (incomplete), so no current could flow through the bulb.
#72
Q:Why is copper wire used in electrical circuits?
- A:Copper is a good conductor of electricity, so electric current can flow through it easily.
#73
Q:Why is electrical wire covered with plastic?
- A:Plastic is an insulator (poor conductor) of electricity, so it prevents electric shock and stops the current from leaking out.
#74
Q:In a series circuit, what happens to the other bulbs if one bulb blows?
- A:All the other bulbs go out, because the circuit becomes open and no current can flow.
#75
Q:In a parallel circuit, what happens to the other bulbs if one bulb blows?
- A:The other bulbs stay lit, because current can still flow through the other complete paths.
#76
Q:Why do two bulbs in series glow more dimly than a single bulb?
- A:The same amount of electricity is shared between two bulbs, so each bulb glows more dimly.
#77
Q:How can you make the bulbs in a circuit brighter?
- A:Add more batteries in series to the circuit.
#78
Q:How would you test whether a material is a conductor of electricity?
- A:Place the material in a circuit with a bulb; if the bulb lights up, the material is a conductor of electricity.
#79
Q:Why should you not touch electrical switches with wet hands?
- A:Water is a conductor of electricity, so the current could flow through the water and your body, giving an electric shock.
#80
Q:What is the function of a switch in a circuit?
- A:A switch opens or closes the circuit to control the flow of current, turning the device off or on.
#81
Q:Why are the prongs of a plug made of metal?
- A:Metal is a good conductor of electricity, allowing current to flow into the appliance.
#82
Q:State the properties of a solid.
- A:A solid has a fixed shape and a fixed volume.
#83
Q:State the properties of a liquid.
- A:A liquid has no fixed shape (it takes the shape of its container) but has a fixed volume.
#84
Q:State the properties of a gas.
- A:A gas has no fixed shape and no fixed volume; it fills up the whole container.
#85
Q:Why did the chocolate turn runny in your hand?
- A:The chocolate gained heat from the hand and melted, changing from solid to liquid.
#86
Q:Why did the water in the freezer turn into ice?
- A:The water lost heat to the cold surroundings and froze, changing from liquid to solid.
#87
Q:Why did bubbles form throughout the water as it was heated strongly?
- A:The water gained heat, reached its boiling point (100°C) and boiled, changing from liquid to gas.
#88
Q:Why did the wet floor become dry after some time?
- A:The water on the floor gained heat and evaporated, changing from liquid into water vapour in the air.
#89
Q:How is evaporation different from boiling?
- A:Evaporation happens slowly at any temperature and only at the surface, while boiling happens quickly at the boiling point and throughout the liquid.
#90
Q:Why did mist form on the cool bathroom mirror?
- A:Warm water vapour in the air lost heat to the cooler mirror and condensed into tiny water droplets.
#91
Q:State three factors that make water evaporate faster.
- A:A higher temperature, more wind/moving air, and a larger exposed surface area.
#92
Q:Why did the volume of water in an open beaker decrease over a few days?
- A:The water gained heat and evaporated into water vapour, which escaped into the air.
#93
Q:Is the white 'steam' you see the same as water vapour?
- A:No. Water vapour is invisible; the white steam is tiny water droplets formed when water vapour condenses.
#94
Q:Describe the water cycle simply.
- A:Water evaporates from seas and rivers, the water vapour rises and condenses into clouds, then falls back to Earth as rain.
#95
Q:What provides the energy that drives the water cycle?
- A:Heat energy from the Sun causes the water to evaporate.
#96
Q:Why do clouds form high up in the sky?
- A:Water vapour rises, loses heat in the cooler air and condenses into tiny water droplets, forming clouds.
#97
Q:State the rule that is true of all matter.
- A:All matter has mass and takes up space (has volume).
#98
Q:How can you change a gas back into a liquid?
- A:Cool it so that it loses heat and condenses.
#99
Q:What stays the same when ice melts into water?
- A:The mass stays the same; only the state changes from solid to liquid.
#100
Q:Why does a balloon shrink when placed in a freezer?
- A:The gas inside loses heat and contracts, taking up less space, so the balloon shrinks.
#101
Q:What does the command word 'State' or 'Identify' require you to do?
- A:Give the answer only — no explanation is needed.
#102
Q:What does the command word 'Explain' require you to do?
- A:Give the reason, using 'because' and a clear cause-and-effect link.
#103
Q:What does the command word 'Describe' require you to do?
- A:State what happens, or the sequence of events, without giving the reason.
#104
Q:What does the command word 'Compare' require you to do?
- A:Mention both things and state how they are similar or different.
#105
Q:What does the number in brackets, e.g. [2], at the end of a question tell you?
- A:It tells you how many distinct points (marking points) your answer should contain.
#106
Q:What is the 'Because–Therefore' answer structure?
- A:[Observation] because [scientific reason], therefore [result/conclusion].
#107
Q:Why must you always link your answer to the exact scenario in the question?
- A:A keyword that is not tied to the specific situation in the question usually scores no mark.
#108
Q:What are the most common ways pupils lose marks even when they know the science?
- A:Repeating the question, using the wrong context, or leaving out the one required keyword.
#109
Q:Improve this answer: 'The water disappeared.'
- A:The water evaporated and changed into water vapour, which mixed into the surrounding air.
#110
Q:Improve this answer: 'It got cold.'
- A:It lost heat to the cooler surroundings, so its temperature decreased.
#111
Q:Improve this answer: 'The metal makes the cold go into the spoon.'
- A:The spoon loses/gains heat — never say an object 'has cold' or that 'cold flows'. Always describe heat being transferred.
#112
Q:Improve this answer: 'The water just got hotter.'
- A:The temperature of the water increased as it gained heat.
#113
Q:When a question gives you data in a table or graph, what must your answer refer to?
- A:Refer to the specific data/values and the trend shown, then explain it using the science concept.
#114
Q:Why is writing 'the plant makes food' not enough for a photosynthesis question?
- A:You must name the process (photosynthesis) and the conditions — light energy, chlorophyll, carbon dioxide and water.
#115
Q:Improve this answer: 'The lights stay on.' (parallel circuit)
- A:Current can still flow through the other complete path, so the remaining bulbs stay lit.
#116
Q:Why does a black object heat up faster in the sun than a white one?
- A:A dark/black surface gains heat from the Sun faster than a light/white surface, so it heats up more quickly.
#117
Q:Why is a layer of air trapped in a winter jacket useful?
- A:Trapped air is a poor conductor of heat, so it reduces the heat lost from the body to the cold surroundings.
#118
Q:Why do the leaves of a plant point towards the light?
- A:Facing the light lets the leaves absorb more light energy for photosynthesis.
#119
Q:Why does chewing food well help digestion?
- A:Chewing breaks food into smaller pieces, giving a larger surface area for digestive juices to act on.
#120
Q:Why does a box on a ramp need a smaller push to start sliding if the ramp is smoother?
- A:A smoother surface produces less friction, so a smaller force is needed to overcome it and move the box.
#121
Q:Why does a heavier object need a larger force to lift it?
- A:A heavier object has a greater weight (more gravitational force acting on it), so a larger force is needed to lift it.
#122
Q:Why does the bulb light up more brightly when a battery is added?
- A:Adding a battery increases the amount of electricity flowing through the bulb, so it lights up more brightly.
#123
Q:Why does a metal lid become easier to open after running it under hot water?
- A:The metal lid gains heat and expands more than the glass, so it loosens and becomes easier to open.
#124
Q:What stays the same and what changes when water boils into steam?
- A:The mass stays the same; only the state changes from liquid to gas.
#125
Q:Improve this answer: 'The seed grows.' (germination question)
- A:The seed germinated because it was given water, air and a suitable temperature (warmth).