PSLE Science 2027.
Connect the ideas.

You should be able to…

• Use several characteristics to distinguish living from non-living things.
• Group organisms using observable similarities and differences.

Key ideas

• Living things need food, water and air, grow, respond to changes and reproduce. Look at these characteristics together: movement alone does not show that something is alive.
• Plants can be grouped into flowering and non-flowering plants. The main animal groups are mammals, birds, fish, insects, reptiles and amphibians. Fungi and bacteria are also living things.
• Use the evidence provided. For example, feathers identify a bird, while an adult insect has six legs. An animal’s habitat alone is not a reliable classification rule.
• Fungi such as mushrooms do not make their own food by photosynthesis. A seed can be alive even before a visible shoot appears. Care for organisms when observing them.

Your turn

An unfamiliar animal has feathers but cannot fly. Which animal group does it belong to? Explain.

You should be able to…

• Compare properties using observations or test results.
• Explain why a material suits a particular use.

Key ideas

• Common materials include wood, metal, ceramic, rubber, glass, plastic and fabric. Name the property needed for a job before choosing a material.
• Strength means supporting a load without breaking. Flexibility means bending without breaking. These are different properties: a strong material need not be flexible.
• Compare whether materials absorb water, float or sink, and allow most, some or no light through. Waterproof material does not absorb water. Do not assume that every sample of a broad material type behaves identically.
• For a fair comparison, use samples of equal dimensions and apply the same test. Explain a choice with the measured property and how it helps the object work.

Your turn

Two equal-sized strips support 4 and 9 identical weights before breaking. Which is stronger in this test?

You should be able to…

• Sequence stages in plant and animal life cycles.
• Compare cycles with and without a pupal stage.

Key ideas

• A flowering plant grows from a seed to a young plant and then an adult plant. The adult can produce seeds, continuing the cycle. A life cycle describes stages, not just increasing size.
• Butterflies, beetles and mosquitoes have egg, larva, pupa and adult stages. Their young look different from the adults. Mosquito larvae and pupae live in water.
• Cockroaches and grasshoppers have egg, nymph and adult stages, with no pupal stage. A nymph resembles the adult but does not yet have all its adult features.
• A chicken develops from an egg into a chick and then an adult. A frog develops from an egg into a tadpole and then an adult frog, with changes to its body and way of living. Compare the actual stages shown in a diagram.

Your turn

Why can removing stagnant water help reduce mosquitoes?

You should be able to…

• Distinguish pollination, fertilisation, dispersal and germination.
• Explain the shared role of reproductive cells in fertilisation.

Key ideas

• Reproduction allows a kind of organism to continue. Offspring inherit many characteristics from their parents. A cell is a basic unit of life.
• In flowering plants, pollination transfers pollen from an anther to a stigma. Fertilisation is the fusion of male and female reproductive cells. After fertilisation, ovules develop into seeds and the ovary develops into a fruit.
• Dispersal moves seeds away from the parent, reducing competition for resources. Wings or hairs can help wind dispersal; hooks can attach to animals; suitable fruits can float or split open. Link the visible feature to how dispersal happens.
• Germination needs water, oxygen and a suitable temperature. A seed initially uses stored food; light is needed later for the young plant to make food. Some plants reproduce using spores rather than seeds.
• In humans, testes produce sperm and ovaries produce eggs. Fertilisation happens when a sperm fuses with an egg. The fertilised egg develops in the womb. Both human and flowering-plant fertilisation involve male and female reproductive cells.

Your turn

Two groups of viable seeds are kept equally warm with access to air. Only one receives water. Why does the dry group fail to germinate?

You should be able to…

• Compare solids, liquids and gases by shape and volume.
• Choose suitable ways to measure mass and volume.

Key ideas

• Matter has mass and occupies space. Air is matter even though it is usually invisible. Light and heat are forms of energy, not matter.
• A solid has a definite shape and volume. A liquid has a definite volume but takes the shape of the part of its container that it occupies. A gas has neither a definite shape nor a definite volume and spreads through the available space.
• Mass is measured with a balance in units such as grams. Liquid volume can be measured with a measuring cylinder in millilitres. Read the scale at eye level and use the correct unit.
• For an object that sinks and does not dissolve or absorb water, its volume can be found from the rise in a measuring cylinder’s water reading after full submersion. Trapped air can prevent water entering an apparently empty container.

Your turn

Why is a syringe of trapped air easier to compress than a syringe filled with water, when both outlets are sealed?

You should be able to…

• Link state changes to heat gain or loss.
• Explain evaporation, condensation and the water cycle.

Key ideas

• Ice melts into water when it gains heat; water freezes into ice when it loses heat. Under ordinary conditions, pure ice melts and pure water freezes at 0°C. Pure water boils at 100°C under normal atmospheric pressure.
• Evaporation happens at the surface and can occur below the boiling point. Boiling occurs throughout the liquid at its boiling point. Water vapour is an invisible gas; visible mist consists of tiny liquid droplets.
• Higher temperature, more wind and a larger exposed surface area generally increase evaporation. To test one factor, keep the other factors and the starting amount of water the same.
• In condensation, water vapour loses heat and becomes liquid. Sunlight supplies energy for evaporation in the water cycle; cooling allows condensation into droplets, which can fall as rain. Water returns to rivers, reservoirs and seas.
• Living things depend on water. Pollution can make water unsuitable for organisms and human use. Conserving water and preventing pollution help protect the supply.

Your turn

A cool lid is held above hot water. Why do droplets form on its underside?

You should be able to…

• Identify roots, stems and leaves.
• Relate each part to the survival of the whole plant.

Key ideas

• Roots anchor a plant and absorb water and mineral salts. Soil supplies water and minerals; it is not the plant’s food.
• The stem supports the plant’s leaves and other parts. It also connects the roots and leaves so substances can be transported around the plant.
• Green leaves make food when suitable conditions are available. Their position helps them receive light. Plant parts work together; damage to one part can affect others.
• When observing a plant, identify the part from its position and function rather than assuming every plant looks identical. Handle plants carefully during investigations.

Your turn

How does a stem help leaves make food?

You should be able to…

• Trace the movement of water and food through a plant.
• Use experimental evidence to explain transport.

Key ideas

• Water-carrying tubes move water absorbed by the roots to the stem and leaves. Food-carrying tubes move food made in the leaves to other parts, including roots, fruits and growing regions.
• Food transport is not always simply downwards. Follow the location where food is made and the parts needing it. Different tubes carry water and food.
• In a coloured-water investigation, coloured regions show where the coloured water travelled. Use the diagram and observations rather than relying on a memorised tube position.
• Plants and humans both transport substances. Plants use tubes for water and food; humans use blood in blood vessels to carry substances around the body.

Your turn

A diagram states that only food-carrying tubes are cut between the leaves and roots. What happens to food supply to the roots?

You should be able to…

• Sequence digestive organs and explain their functions.
• Recognise the main roles of the body’s systems.

Key ideas

• The digestive system breaks food into simpler substances that the body can absorb. Food passes through the mouth, gullet, stomach, small intestine and large intestine.
• In the mouth, chewing breaks food into smaller pieces and saliva begins digestion. The gullet moves food to the stomach, where further digestion takes place.
• Digestion is completed in the small intestine, where digested food is absorbed into the blood. The large intestine absorbs water from undigested material. Undigested material is eventually passed out.
• Other systems have different jobs: the respiratory system exchanges gases; the circulatory system transports substances; the skeletal system supports and protects; muscles help the body move. Systems work together.

Your turn

Which part absorbs digested food, and which system carries it around the body?

You should be able to…

• Explain the roles of lungs, heart, blood and blood vessels.
• Connect digestion, gas exchange and transport.

Key ideas

• Air contains several gases, including nitrogen, oxygen, carbon dioxide and water vapour. Inhaled and exhaled air are both mixtures; exhaled air is not pure carbon dioxide.
• Air enters through the nose and passes along the windpipe to the lungs. Oxygen passes into the blood at the lungs; carbon dioxide passes from the blood into the lungs to be breathed out.
• The heart pumps blood through blood vessels. Blood transports oxygen and digested food to body parts and carries carbon dioxide away. Faster activity can increase the demand for oxygen and energy.
• Plants, fish and humans all take in oxygen and give out carbon dioxide during respiration. Humans use lungs, most fish use gills, and plants exchange gases through openings, including tiny openings in leaves.
• Breathing moves air in and out. Respiration releases energy from food. Digestion provides absorbable food, the respiratory system supplies oxygen, and circulation connects them to the body’s parts.

Your turn

Explain how oxygen reaches a leg muscle after being breathed in.

You should be able to…

• Identify a complete conducting path.
• Compare simple series and parallel bulb arrangements.

Key ideas

• A simple electrical system includes a battery, wires and a component such as a bulb. A closed switch completes a conducting path; an open switch breaks it. A working bulb lights only when current passes through it.
• Trace a path from one battery terminal, through the bulb’s two different contacts, and back to the other terminal. A wire touching the same contact twice does not make the required path through the bulb.
• Electrical conductors allow current to pass; electrical insulators do not readily do so. Metals commonly conduct electricity, while plastic and rubber are used to insulate wires.
• With identical working components in the usual simple circuits, more batteries connected correctly in series can make a bulb brighter. More bulbs in series generally make each dimmer.
• Parallel branches provide separate paths. Opening one bulb’s branch need not break another branch. Compare brightness only when the battery arrangement and other conditions are specified. Use low-voltage school equipment; never experiment with mains sockets.

Your turn

A plastic strip placed in a gap prevents a test bulb lighting. A metal strip makes it light. What can you conclude?

You should be able to…

• Predict attraction and repulsion.
• Distinguish magnets from magnetic materials.

Key ideas

• A magnet has a north and a south pole. Like poles repel; unlike poles attract. Magnetic forces can act without the objects touching.
• Magnets attract magnetic materials such as iron and steel. Not every metal is magnetic: a material can conduct electricity yet not be attracted by a magnet.
• A freely suspended bar magnet settles approximately along the north–south direction. Magnets are useful in objects such as magnetic catches and compasses.
• An iron or steel object being attracted is not by itself proof that it is a magnet. Repulsion by a known magnet is stronger evidence that the tested object is also a magnet.
• A magnet can be made by repeatedly stroking a suitable object in one direction with one pole. An electrical method uses a coil carrying current around a suitable iron core; disconnect the low-voltage supply after use.

Your turn

A steel paper clip is attracted to both poles of a magnet. Must the paper clip itself be a magnet?

You should be able to…

• Explain changes in motion or shape using forces.
• Interpret friction and spring investigations.

Key ideas

• A force is a push or pull. It can start or stop motion, change speed or direction, or change an object’s shape. Several forces can act at once.
• Gravity pulls objects towards Earth and gives them weight. It acts even when an object is supported or moving upwards.
• Friction between sliding surfaces opposes their relative motion. It can help shoes grip the ground or slow a sliding object. Compare surfaces using the same object and release conditions.
• A stretched or compressed spring exerts an elastic spring force tending to restore its shape. Adding a larger load usually stretches a spring farther within its working range.
• Measure extension as stretched length minus original length. A spring’s total length is not its extension. Use observations to compare springs rather than assuming they stretch equally.

Your turn

Identical blocks slide from the same starting speed across two surfaces. One stops sooner. What is a possible explanation?

You should be able to…

• Explain food webs and changes in populations.
• Connect adaptations and conservation to survival.

Key ideas

• An organism is one living thing. A population is organisms of the same kind living and reproducing in the same place and time. A community contains different populations living together; a habitat is the place where an organism lives.
• Survival depends on temperature, light, water, food and other organisms. Different habitats support different communities. If conditions become unsuitable, organisms may survive through suitable adaptations or responses, move elsewhere, or die.
• Producers such as green plants make food. Consumers eat other organisms. Decomposers break down dead matter and waste, returning materials to the environment. Food-chain arrows point from food to the organism eating it, showing energy transfer.
• Food webs link multiple chains. When predicting a population change, identify the actual feeding link, food supply and predators. State “may” when other factors could affect the result.
• Structural adaptations are body features; behavioural adaptations are actions. Link a feature or action to obtaining food, avoiding predators, coping with conditions or reproducing. An individual does not instantly choose to grow a new body feature.
• Pollution, deforestation and overuse of resources can damage habitats. Global warming can change environmental conditions. Conservation and reforestation help protect organisms and resources; explain the particular benefit rather than just saying “save nature”.

Your turn

A seed has a broad wing. Explain how this feature can improve the offspring’s chance of survival.

You should be able to…

• Trace the path of light that allows us to see.
• Explain changes in a shadow using the setup.

Key ideas

• We see a light source when its light enters our eyes. We see a non-luminous object when light reflects from it into our eyes. Eyes do not send out light to see objects.
• Light travels in straight lines. A shadow forms where an object completely or partly blocks light from reaching a surface.
• Shadow shape depends on the object’s shape and orientation. Size depends on distances between the light source, object and screen.
• With a small light source and fixed screen, moving an object towards the source generally enlarges its shadow; moving it towards the screen generally makes the shadow smaller. Always check which distances change.
• Materials letting most light through produce different shadows from those blocking most light. Draw straight lines from the source past the object’s edges to reason about the dark region.

Your turn

A lamp and screen stay fixed. An object moves closer to the lamp. What usually happens to its shadow size?

You should be able to…

• Distinguish heat from temperature.
• Explain heat transfer, expansion and insulation.

Key ideas

• Heat is energy transferred because of a temperature difference. Temperature measures how hot or cold something is. Use a thermometer or temperature sensor to measure it.
• Heat flows from hotter to colder objects or surroundings until they reach the same temperature. An object can gain or lose heat; explain both the source and destination.
• Heat gain can raise temperature, cause expansion or change state. Heat loss can lower temperature, cause contraction or change state. Temperature does not necessarily rise during melting or boiling.
• Metals are generally good conductors of heat. Wood, plastic, rubber and air are poor conductors. An insulating layer slows heat transfer; it does not produce cold or stop all heat transfer.
• Solids, liquids and gases generally expand when heated and contract when cooled. Use the stated material and conditions, since a change of state can behave differently from ordinary warming or cooling.

Your turn

A metal lid is warmed and becomes easier to loosen. Suggest why.

You should be able to…

• Identify the requirements and products of photosynthesis.
• Distinguish making food from releasing energy from food.

Key ideas

• Green plants use light energy, water and carbon dioxide to make sugar and release oxygen during photosynthesis. The Sun is the main source of light and heat for life on Earth.
• Plants make food; animals obtain food by eating plants or other animals. Both plants and animals release energy from food through respiration to carry out life processes.
• Photosynthesis requires light. Respiration happens in living plants during both day and night. Do not assume a plant stops needing oxygen when it is in sunlight.
• To investigate a requirement, change only that factor and keep others similar. If using oxygen bubbles from a water plant as evidence, compare the same observation time and remember that bubble sizes may vary.
• Food made in leaves can be transported to growing or storage parts. Photosynthesis links plant transport, respiration and the energy entering food chains.

Your turn

Does a plant respire in the dark? Can it photosynthesise then?

You should be able to…

• Trace energy changes in everyday systems.
• Explain why conserving energy resources matters.

Key ideas

• Recognise kinetic, potential, light, electrical, sound and heat energy. Moving objects have kinetic energy; energy can be stored as potential energy, for example in a raised object, stretched spring, food or battery.
• Trace energy through the actual system. A battery-powered torch converts stored potential energy to electrical energy, then light and heat. Include relevant outputs rather than assuming all energy becomes useful light.
• A falling object loses stored potential energy as it gains kinetic energy. On impact, some energy transfers to the surroundings as sound and heat. Energy does not simply vanish when motion stops.
• Energy from many resources can be traced to the Sun. Plants store energy from sunlight in food; animals obtain energy through feeding. Many fuels originated from once-living organisms.
• Some resources can be depleted. Switching off unused appliances and using energy efficiently reduce resource use. Distinguish conserving usable resources from the scientific idea that energy is transferred or converted.

Your turn

Give an energy pathway for sunlight powering a solar-panel fan.

You should be able to…

• Plan a fair comparison and interpret its results.
• Support explanations with evidence and acknowledge limitations.

Key ideas

• Start with a question you can investigate. A prediction states what you expect; a hypothesis proposes a testable explanation or relationship. Make clear what you change and what you measure.
• Change one intended factor in a fair comparison and identify the relevant conditions to keep the same. Give actual conditions, such as water volume or sample size, rather than saying only “keep everything else constant”.
• Use suitable apparatus and units. Read scales carefully, use the same procedure and repeat measurements. Repetition helps reveal inconsistent results; it cannot fix a method that compares unequal conditions.
• For tables and graphs, check labels, units and scales. Describe the trend within the measured range and support it with selected values. Do not assume a trend continues indefinitely beyond the evidence.
• Distinguish an observation from an inference. An observation reports what was measured or seen. An inference interprets it. A conclusion should answer the investigation question and stay within what the results support.
• When evaluating a method, name a specific weakness and explain how a change helps. In written answers, connect the evidence, scientific idea and result. A list of keywords is not a causal explanation.

Your turn

A spring measures 8 cm with no load, 10 cm with one weight and 12 cm with two identical weights. State a supported trend and one limit.