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PSLE Science study materials
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PSLE Science practice questions

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Question 1Science

Which part of a plant absorbs most of the water it needs?

  1. The flowers
  2. The leaves
  3. The roots Correct answer.
  4. The stem

Explanation

Roots are the plant organs that take in water and dissolved mineral salts from the soil. They have many fine root hairs that increase the surface area for absorption. Water then travels up the stem to the rest of the plant.

Question 2Science

A boy pushes a box and it slides across a smooth floor. What force slows the box down?

  1. Gravity pulling it forward
  2. Magnetism from the floor
  3. Friction between the box and the floor Correct answer.
  4. Air pushing it from above

Explanation

Friction acts between two surfaces in contact and opposes the sliding motion, so the box gradually slows. A smoother floor gives less friction, so the box slides farther. Gravity pulls downward and does not slow forward motion in this case.

Question 3Science

Which of these materials is the best conductor of electricity?

  1. Rubber
  2. Glass
  3. Copper Correct answer.
  4. Dry wood

Explanation

Metals such as copper contain free electrons that can carry electric current easily, making them good conductors. Wood, rubber and glass do not allow current to flow well and are used as insulators. This is why electrical wires are made of copper.

Question 4Science

What happens to water when it is cooled to 0 degrees Celsius?

  1. It evaporates into the air
  2. It freezes and becomes ice Correct answer.
  3. It melts into liquid
  4. It boils and becomes steam

Explanation

Cooling water to its freezing point of 0 degrees Celsius changes it from liquid to solid, forming ice. This change of state is called freezing. The particles become fixed in place instead of moving freely.

Question 5Science

Which organ pumps blood around the human body?

  1. The stomach
  2. The heart Correct answer.
  3. The lungs
  4. The kidneys

Explanation

The heart is a muscular organ that contracts to pump blood through blood vessels to all parts of the body. Blood carries oxygen and nutrients to cells and removes waste. Other organs have different jobs in the body.

Question 6Science

A ball is dropped from a height. Which statement best describes its energy as it falls?

  1. It loses all its energy
  2. It gains energy from the ground
  3. Its stored energy changes to movement energy Correct answer.
  4. Its energy stays exactly the same form

Explanation

A raised object has gravitational potential energy stored because of its height. As it falls, this energy changes into kinetic (movement) energy, so the ball speeds up. The total energy is conserved, but its form changes.

Question 7Science

Which of these animals is a mammal?

  1. A crocodile
  2. A dolphin Correct answer.
  3. A shark
  4. A frog

Explanation

Mammals are warm-blooded animals that breathe air, have hair or fur, and feed their young with milk. Dolphins give birth to live young and feed them milk, so they are mammals even though they live in water. The other animals are not mammals.

Question 8Science

Why does a metal spoon left in a hot drink become warm?

  1. Heat is carried along the spoon by conduction Correct answer.
  2. Light from the room warms the spoon
  3. The spoon makes its own heat
  4. Cold moves from the spoon into the drink

Explanation

Conduction is the transfer of heat through a solid material when its particles vibrate and pass energy along. Metal conducts heat well, so heat travels from the hot drink up the spoon. This is why the handle soon feels warm.

Question 9Science

A plant is kept in a dark cupboard for a week. What is the most likely result?

  1. Its leaves turn yellow and it grows poorly Correct answer.
  2. It produces more flowers
  3. It grows faster than before
  4. Its roots stop absorbing water immediately

Explanation

Plants need light for photosynthesis to make food. Without light, the plant cannot make enough food, so its leaves lose their green colour and growth slows. Roots still absorb water, but the plant weakens overall.

Question 10Science

Two identical boxes are pushed with the same force, one on a rough surface and one on a smooth surface. Which box is harder to keep moving, and why?

  1. Neither moves, because friction always stops motion
  2. The box on the rough surface, because friction is greater Correct answer.
  3. Both are equally hard, because the force is the same
  4. The box on the smooth surface, because it slides too fast

Explanation

A rough surface creates more friction between the box and the surface, and friction opposes motion. Greater friction means a larger force is needed to keep the box moving. On a smooth surface there is less friction, so it is easier to push.

Question 11Science

A mixture of sand and salt is stirred into water. Which method best separates the sand from the salty water?

  1. Stirring the mixture faster
  2. Filtering the mixture through filter paper Correct answer.
  3. Cooling the mixture in a fridge
  4. Heating the mixture until it boils

Explanation

Sand does not dissolve in water, so its particles are trapped by filter paper while the salty water passes through. This process is filtration. The salt stays dissolved and cannot be removed this way.

Question 12Science

A balloon rubbed on a woollen jumper sticks to a wall. What causes this?

  1. The balloon loses all its air
  2. The wall becomes heavier
  3. Static electricity builds up on the balloon Correct answer.
  4. The balloon becomes magnetic

Explanation

Rubbing transfers tiny charged particles between the balloon and the jumper, building up static electricity. The charged balloon then attracts the neutral wall, so it sticks. This is an electrical effect, not magnetism.

Question 13Science

Ice is left in an open bowl at room temperature. After some hours the bowl contains less water than the original ice. Why?

  1. The water was absorbed by the bowl
  2. The water was used up by the air
  3. The ice turned into a gas without melting
  4. Some water evaporated into the air as vapour Correct answer.

Explanation

The ice melts to water, and some of that water gains heat and evaporates, becoming water vapour that mixes with the air. Because the vapour leaves the bowl, less water remains. The bowl does not absorb the water.

Question 14Science

A student adds more bulbs in series to a simple circuit with one battery. What happens to the brightness of each bulb?

  1. The bulbs give out no light at all
  2. The brightness stays the same
  3. Each bulb becomes dimmer Correct answer.
  4. Each bulb becomes brighter

Explanation

In a series circuit the bulbs share the battery's voltage, and adding more bulbs increases the total resistance. The current through the circuit falls, so each bulb receives less energy and glows dimmer. The bulbs still light up, but weakly.

Question 15Science

Which food group is the body's main source of energy for daily activities?

  1. Water
  2. Carbohydrates Correct answer.
  3. Minerals
  4. Vitamins

Explanation

Carbohydrates such as rice, bread and potatoes are broken down into sugars that cells use for energy. They supply most of the energy for movement and growth. Vitamins, minerals and water are needed for health but provide little or no energy.

Question 16Science

A tadpole develops into a frog. Which change correctly describes this process?

  1. It loses its tail and develops legs Correct answer.
  2. It grows wings for flying
  3. It keeps its gills and tail as an adult
  4. It changes from a frog into a tadpole

Explanation

A frog undergoes metamorphosis: the tadpole hatches with gills and a tail, then develops legs and lungs and its tail shrinks. The adult frog lives on land and in water. This change is a normal part of its life cycle.

Question 17Science

A seed is planted deep in dry soil and given no water. Which condition is missing that prevents germination?

  1. Soil particles
  2. Warmth only
  3. Water Correct answer.
  4. Light

Explanation

Seeds need water, warmth and air to germinate; light is not usually required. Without water the seed cannot soften its coat or start growing. Dry soil therefore prevents germination even if it is warm.

Question 18Science

A metal lid on a glass jar is stuck. Running hot water over the metal lid loosens it. Why?

  1. The glass shrinks quickly in hot water
  2. The metal expands more than the glass when heated Correct answer.
  3. The hot water melts the metal
  4. The water acts as a glue remover

Explanation

Heating makes materials expand, and metals generally expand more than glass for the same temperature rise. The metal lid grows slightly larger than the jar opening, so it becomes easier to turn. This is a common use of thermal expansion.

Question 19Science

Which statement correctly compares mass and weight?

  1. Mass changes with location but weight does not
  2. Weight is measured in kilograms and mass in newtons
  3. Mass and weight are the same quantity
  4. Mass is the amount of matter, while weight is the pull of gravity on it Correct answer.

Explanation

Mass measures how much matter an object contains and stays the same everywhere. Weight is the gravitational force on that mass and can change if gravity changes, such as on the Moon. Mass is measured in kilograms and weight in newtons.

Question 20Science

A food chain is: grass, then grasshopper, then frog, then snake. If the frogs are removed, what is the most likely immediate effect?

  1. The grasshopper population may increase Correct answer.
  2. The grass will disappear quickly
  3. The snake population will grow at once
  4. The grass will start eating grasshoppers

Explanation

Frogs eat grasshoppers, so removing frogs reduces predation on grasshoppers and their numbers may rise. More grasshoppers could then eat more grass. The snake, which eats frogs, would lose food rather than gain it.

Question 21Science

A block floats with half its volume under water. What can be concluded about the block?

  1. Its density equals the density of water Correct answer.
  2. It is heavier than the same volume of water
  3. It has no mass at all
  4. Its density is greater than water's density

Explanation

A floating object displaces water whose weight equals the object's weight. If half the block is submerged, the block's average density is half that of water, not equal; the key rule is that a floating object is less dense than the liquid. Since it floats, its density must be lower than water's, so the block is not heavier than an equal volume of water.

Question 22Science

A plant is placed in bright light and its leaves are tested for starch at the end of the day. Which result is expected and why?

  1. Starch is absent because light destroys starch
  2. Starch is present because photosynthesis made food in the light Correct answer.
  3. Starch is absent because leaves store only water
  4. Starch is present because the roots made it in the dark

Explanation

In bright light, leaves carry out photosynthesis and make glucose, some of which is stored as starch. Testing the leaves with iodine turns them blue-black, showing starch is present. Light is needed for this food-making process.

Question 23Science

Two circuits each have one battery. Circuit A has two bulbs in series; Circuit B has the same two bulbs in parallel. Which statement is correct?

  1. Bulbs in B are brighter because each gets the full battery voltage Correct answer.
  2. Bulbs in B do not light at all
  3. Bulbs in A are brighter because the current is larger
  4. Both circuits give exactly the same brightness

Explanation

In a parallel circuit each branch is connected directly across the battery, so each bulb receives the full voltage and glows brightly. In series, the voltage is shared between bulbs, so each is dimmer. Parallel bulbs therefore appear brighter.

Question 24Science

A student heats a beaker of water and records that its temperature stays at 100 degrees Celsius while it boils. What does this show?

  1. The water has stopped gaining heat
  2. The heat is used to change water into steam, not to raise temperature Correct answer.
  3. The thermometer is broken
  4. Boiling water cannot contain heat

Explanation

During boiling, heat energy is used to overcome the forces holding liquid particles together so they become gas. This energy changes the state rather than raising the temperature, so the reading stays constant. Once all the water has boiled away, added heat would raise the temperature of the steam.

Question 25Science

A population of insects develops resistance to a pesticide after many generations. Which explanation fits the idea of natural selection?

  1. The pesticide taught the insects to resist it
  2. All insects chose to become resistant
  3. Insects with natural resistance survived and passed it on Correct answer.
  4. The insects grew resistant because they were sprayed

Explanation

Some insects already carry variations that make them less affected by the pesticide. These survive and reproduce, passing the helpful trait to their young, so the population becomes mostly resistant over generations. This is natural selection acting on existing variation.

Question 26Science

Which part of the human digestive system absorbs most of the water from undigested food?

  1. Large intestine Correct answer.
  2. Oesophagus
  3. Small intestine
  4. Stomach

Explanation

Most water is absorbed back into the body through the walls of the large intestine, which turns the remaining waste into solid faeces. The small intestine absorbs digested nutrients rather than the bulk of the water.

Question 27Science

A pupil looks at a lit candle through a straight cardboard tube. What property of light allows the flame to be seen this way?

  1. Light can bend around corners
  2. Light is a form of heat
  3. Light travels in straight lines Correct answer.
  4. Light can pass through all materials

Explanation

Because light travels in straight lines, it can only reach the eye along a clear straight path through the tube. If the tube is bent, the straight-line path is blocked and the flame cannot be seen.

Question 28Science

Which group of vertebrates has dry, scaly skin and lays eggs with leathery shells on land?

  1. Reptiles Correct answer.
  2. Amphibians
  3. Birds
  4. Fish

Explanation

Reptiles such as lizards and turtles have dry, scaly skin that reduces water loss, and they lay shelled eggs on land. These features allow them to live away from water.

Question 29Science

A magnet is moved slowly towards a pile of paper clips. What is observed as it gets closer?

  1. More clips jump to the magnet Correct answer.
  2. The clips turn into magnets of the same pole
  3. The clips repel the magnet
  4. The clips become heavier

Explanation

The magnetic force is stronger nearer the magnet, so it can pull more clips from a greater distance as it approaches. At a distance the force is too weak to lift them.

Question 30Science

Which process in the water cycle changes water vapour in the air into tiny droplets that form clouds?

  1. Melting
  2. Filtration
  3. Evaporation
  4. Condensation Correct answer.

Explanation

Condensation happens when water vapour cools and turns back into liquid droplets, which gather as clouds. Evaporation is the opposite change, from liquid to vapour.

Question 31Science

A boy pushes a heavy box but it does not move at all. Which statement about the forces is correct?

  1. There is no friction acting on the box
  2. The pushing force is larger than friction
  3. The pushing force is balanced by friction Correct answer.
  4. The box has no weight

Explanation

When an object stays still, the forces on it are balanced. The push is matched by an equal friction force in the opposite direction, so the box does not move.

Question 32Science

Which structure in a flowering plant produces pollen?

  1. Stamen Correct answer.
  2. Root hair
  3. Ovary
  4. Sepal

Explanation

The stamen is the male part of the flower and its anther produces pollen grains. Pollen is later transferred to the female part during pollination.

Question 33Science

Which material is the best conductor of heat among these?

  1. Plastic
  2. Wood
  3. Rubber
  4. Copper Correct answer.

Explanation

Metals such as copper contain free electrons that carry heat quickly through the material, making them good conductors. Wood, rubber and plastic are poor conductors used as insulators.

Question 34Science

A plant stem is placed in water coloured with red dye. After a day, red streaks appear in the leaves. Which tissue carried the dye upward?

  1. Root hairs
  2. Flower petals
  3. Outer bark
  4. Xylem tubes Correct answer.

Explanation

Xylem tubes are narrow vessels that carry water and dissolved substances from the roots up the stem to the leaves. The coloured dye shows the path of water transport.

Question 35Science

A student connects a battery, a bulb and a switch. The bulb lights only when the switch is closed. Why does opening the switch stop the bulb?

  1. The bulb becomes a conductor
  2. The circuit is broken so current cannot flow Correct answer.
  3. The battery loses all its energy instantly
  4. The current changes direction

Explanation

Current needs a complete closed loop to flow. Opening the switch creates a gap, so the circuit is incomplete and no current reaches the bulb.

Question 36Science

A student blows air into a balloon. The balloon gets bigger. What happens to the air inside?

  1. It is compressed into a smaller space per particle Correct answer.
  2. It disappears as it enters
  3. It gains more mass than was blown in
  4. It turns into a liquid

Explanation

Air is a gas and can be compressed, so the same amount of gas is squeezed into the balloon, increasing the pressure inside. The particles are pushed closer together than in the open air.

Question 37Science

A block of wood and a block of iron of the same size are placed in water. The iron sinks and the wood floats. Which explanation is best?

  1. Water pushes wood down
  2. Wood has more mass than iron
  3. Iron is colder than water
  4. Iron has a greater density than water Correct answer.

Explanation

An object sinks when its density is greater than the liquid's density. Iron is denser than water so it sinks, while wood is less dense than water so it floats.

Question 38Science

A child sits on a see-saw exactly in the middle and the see-saw stays level. A heavier child then sits on one end. What happens?

  1. The heavier end goes down Correct answer.
  2. The see-saw stays level
  3. The lighter end goes down
  4. The see-saw spins around

Explanation

A see-saw balances when the turning effects on both sides are equal. A heavier child on one end creates a larger turning effect, so that end drops.

Question 39Science

A boy walks 300 metres east and then 100 metres west. What is his displacement from the starting point?

  1. 100 metres west
  2. 400 metres east
  3. 300 metres east
  4. 200 metres east Correct answer.

Explanation

Displacement is the straight-line distance and direction from start to finish. The eastward 300 metres minus the westward 100 metres leaves 200 metres east of the start.

Question 40Science

A student observes that a caterpillar changes into a butterfly inside a hard case. Which term describes this change?

  1. Metamorphosis Correct answer.
  2. Germination
  3. Fermentation
  4. Pollination

Explanation

Metamorphosis is the change of body form during the life cycle of animals such as butterflies. The caterpillar becomes a pupa and later emerges as an adult butterfly.

Question 41Science

A pot of water is heated and a thermometer shows its temperature rising steadily. Which statement about the heat energy added is correct?

  1. It lowers the temperature of the water
  2. It removes particles from the water
  3. It increases the average movement of water particles Correct answer.
  4. It has no effect on the particles

Explanation

Heating gives particles more kinetic energy, so they move faster and the temperature rises. Temperature is a measure of the average motion of particles.

Question 42Science

Two identical plants are kept in the same room. Plant A is watered daily; Plant B is not watered. After two weeks, Plant B wilts. Which reason best explains the wilting?

  1. The roots grow longer
  2. Cells lose water and become less firm Correct answer.
  3. The plant makes too much food
  4. Cells gain extra water and swell

Explanation

Water keeps plant cells firm, which supports the stem and leaves. Without water, cells lose turgor and the plant droops or wilts.

Question 43Science

A student mixes vinegar and baking soda in a cup and sees bubbles fizzing out. What kind of change has occurred?

  1. Only a change in colour
  2. No change at all
  3. A chemical change producing a gas Correct answer.
  4. A physical change of state

Explanation

Bubbles of a new gas show that a new substance is being formed, which is a sign of a chemical change. Physical changes do not create new substances.

Question 44Science

A food web contains grass, rabbits, foxes and owls. If the foxes are removed, which change is most likely?

  1. The rabbit population may increase Correct answer.
  2. The owls will eat only grass
  3. The grass population will increase at once
  4. The rabbits will become herbivores

Explanation

With fewer predators, more rabbits survive and reproduce, so their numbers rise. More rabbits then eat more grass, so grass may decrease later.

Question 45Science

A pupil uses a mirror to see around a corner. Which property of light makes this possible?

  1. Light is absorbed by mirrors
  2. Light cannot change direction
  3. Light travels only in curves
  4. Light can be reflected Correct answer.

Explanation

A mirror reflects light, so light from an object can bounce off the mirror into the eye even when the object is hidden. This lets the pupil see around a corner.

Question 46Science

A circuit has a battery and two bulbs in parallel. One bulb is removed. What happens to the other bulb?

  1. It becomes much brighter
  2. It stays lit at about the same brightness Correct answer.
  3. It goes out completely
  4. It flickers on and off

Explanation

In a parallel circuit each branch has its own path to the battery, so removing one bulb does not break the other branch. The remaining bulb still gets the full battery voltage and stays lit.

Question 47Science

An object is placed in front of a plane mirror. The object is moved 20 centimetres closer to the mirror. How does the image change?

  1. It moves 40 centimetres away
  2. It becomes upside down
  3. It moves 20 centimetres closer to the mirror Correct answer.
  4. It stays in the same place

Explanation

A plane mirror forms an image as far behind the mirror as the object is in front. Moving the object 20 centimetres closer moves the image 20 centimetres closer as well.

Question 48Science

A sealed syringe contains air. The plunger is pushed in but the air cannot escape. What happens to the pressure of the air inside?

  1. It stays the same because the amount of air is fixed
  2. It decreases because there is less air
  3. It increases because particles hit the walls more often Correct answer.
  4. It drops to zero

Explanation

Squeezing the air into a smaller volume makes the particles hit the walls more frequently, so the pressure rises. The number of particles is unchanged but the space is smaller.

Question 49Science

Two identical carts roll down two ramps of the same height, one steep and one gentle, and start from rest. Ignoring friction, how do their speeds at the bottom compare?

  1. The gentle-ramp cart is faster
  2. The steep-ramp cart is faster
  3. They are equal Correct answer.
  4. The steep-ramp cart has twice the speed

Explanation

Both carts start from the same height, so they lose the same amount of gravitational potential energy. Without friction, this becomes the same kinetic energy, giving equal speeds at the bottom.

Question 50Science

A plant is kept in a sealed transparent container with a small amount of carbon dioxide. In bright light, the carbon dioxide level falls during the day. Which process explains this?

  1. Transpiration releases carbon dioxide
  2. Digestion uses carbon dioxide
  3. Photosynthesis uses carbon dioxide Correct answer.
  4. Respiration releases carbon dioxide

Explanation

In bright light, photosynthesis uses carbon dioxide and water to make food, so the carbon dioxide in the container falls. Respiration also occurs but releases carbon dioxide more slowly than photosynthesis uses it in strong light.