PSLE Science — Exam Cheatsheet
Created by Miss Clarissa Ng | www.clartutors.com
EXAM How the Paper Works
| Part | Questions | Marks per Q | Total Marks |
|---|---|---|---|
| Booklet A — multiple choice (4 options) | 30 questions | 2 marks each | 60 |
| Booklet B — open-ended / structured | 10 questions (reduced from 12–13 in previous years) | — | 40 |
| Total | 40 questions | 100 marks · 1 h 45 min |
New PSLE format this year: Booklet A now has 30 MCQs at 2 marks each = 60 marks — that is 60% of the whole paper. It also features linked multiple-choice questions that share a common experimental setup or scenario. Booklet B is reduced to 10 structured questions (40 marks).
Pacing: MCQs are worth 2 marks each and 60% of the overall score — do not rush them. ~3 min per MCQ in Booklet A, ~5–6 min per structured question in Booklet B. In linked MCQ sets, read the shared setup once carefully before answering each part.
LIFE · 1 Organisms & Classification very high frequency
Characteristics of living things (6)
- Living things need air, food and water to survive
- Living things grow (in height / length / mass)
- Living things reproduce (population size / no. of organisms increases)
- Living things respond to changes around them
- Living things move by themselves
- Living things die (population size / no. of organisms decreases)
The classic trap: "Which is a characteristic of ALL living things?" → the answer is always they can reproduce. NOT "make food" (animals don't), NOT "move by themselves" (plants don't).
Classification of animals — know these groupings cold
| Group | Outer Covering | Breathing | Reproduction |
|---|---|---|---|
| 🐘 Mammals | Hair or fur | Lungs | Most give birth to young alive |
| 🐦 Birds | Feathers 🪶 | Lungs | Lay eggs 🥚 |
| 🐟 Fish | Scales | Gills | Most lay eggs 🥚 |
| 🐛 Insects | Hard outer covering | Breathing holes / tubes | Most lay eggs 🥚 |
| 🦎 Reptiles | Dry skin with scales | Lungs | Most lay eggs 🥚 |
| 🐸 Amphibians | Moist skin | Lungs + moist skin | Lay eggs 🥚 |
Unique characteristics — how to tell them apart
🐘Mammals
- Covered with hair or fur
- Feed their young with milk 🍼
🐦Birds
- Covered with feathers 🪶
- Have a beak
🐛Insects
- Three body parts: head, thorax and abdomen
- Six legs attached to the thorax
Common characteristics of ALL animals: they are living things — need air, food and water; grow; reproduce; respond to changes around them; move by themselves; die. They also cannot make their own food, so they take in food from other organisms (plants or animals).
How it's asked: "Which feature is used to tell the two animals apart?" → use one column of the table above (e.g. outer covering, breathing organ). Insects are the only group with NO backbone.
Flowering vs non-flowering plants
| 🌸 Flowering Plants | 🌿 Non-Flowering Plants | |
|---|---|---|
| Reproduction | By seeds 🌱 | By spores 🍂 |
| Making Food | Both make their own food through photosynthesis ☀️🌿 | |
Fungi & bacteria — the decomposers
| 🍄 Fungi | 🦠 Bacteria | |
|---|---|---|
| Reproduction | By spores | By splitting into two |
| How they obtain food | Both obtain food from other dead or living things (cannot make their own food) | |
Decomposers: fungi & bacteria break down dead plants and animals into simpler substances. Both need warmth, air and moisture to grow.
LIFE · 2 Reproduction & Heredity very high frequency
The sequences
- Plants: seed dispersal → germination → pollination → fertilisation
- Humans: fertilisation = male cell + female cell fuse to form a zygote (fertilised egg)
Where the cells are made (memorise this row)
| Male cell | Female cell | |
|---|---|---|
| Humans / animals | sperm — produced by the testes | egg cell — produced by the ovary |
| Flowering plants | pollen grain (carries the male reproductive cell) — from the anther | ovule (contains the female reproductive cell) — inside the ovary |
Flower parts & what they become
| Part | Role | Becomes after fertilisation |
|---|---|---|
| Petal | attracts insects / birds (colour, scent) | wilts & falls off |
| Anther | makes pollen grains | — |
| Stigma | receives the pollen grain (sticky) | — |
| Style | pollen tube grows down through it | — |
| Ovary | holds the ovules | fruit |
| Ovule | contains the female reproductive cell | seed |
One ovary + many ovules → one fruit with many seeds. A fruit made of many small seeds packed together (e.g. a papaya) came from a flower with one ovary and many ovules.
How it's asked: "Name the process that must happen AFTER pollination to produce seeds." → fertilisation. (Pollination = pollen grain lands on the stigma; fertilisation = male reproductive cell joins with female reproductive cell in the ovule. They are NOT the same.)
- Heredity: offspring inherit traits from BOTH parents — that's why siblings look similar but not identical.
- "What is common to sexual reproduction in plants and humans?" → both need a male cell + female cell fusing (fertilisation).
LIFE · 3 Reproduction in Plants — Seeds & Dispersal high frequency
Germination needs (all three)
- Water + oxygen + warmth. Light is NOT required for germination.
How it's asked: "What is the function of seed leaves?" → they provide food for the SEEDLING until its own leaves develop.
Seed dispersal — match structure to method
| Method | Adaptation on the seed/fruit | Example |
|---|---|---|
| Wind | wing-like structures or fine hairs | dandelion (fine hairs), maple seed (wing-like structure) |
| Animals (eat it) | fleshy, sweet fruit | mango, cherry |
| Animals (attach) | hooks / spikes | burdock — cling to fur |
| Explosive action | dry pod that splits open when ripe — flings seeds away | pea plant |
| Water | fibrous husk + waterproof outer covering — floats on water | coconut |
How it's asked: "Fruit X has hooks, fruit Y has wing-like structures. Which zone is each more likely found in?" → Hooks = near animals/paths (animal dispersal); wing-like structures / fine hairs = open, windy areas (wind dispersal). Always give the reason, not just the zone.
- Pollination agents: insects/birds are attracted by bright petals + scent + nectar. Wind-pollinated flowers have no bright petals, lots of light pollen.
LIFE · 4 Reproduction in Humans medium frequency
| Structure | Function |
|---|---|
| Ovary | produce egg cells |
| Fallopian tube | site of fertilisation |
| Womb | site where the fertilised egg develops |
| Vagina / birth canal | where sperm is deposited |
Fertilisation happens in the fallopian tube, NOT the womb. The fertilised egg then travels to and develops in the womb. A common "which statement is not correct" trap.
LIFE · 5 Life Cycles very high frequency
Count the stages — VERY IMPORTANT TO TAKE NOTE
| Type | Stages | Examples |
|---|---|---|
| Three-stage | egg → young (nymph) → adult (NO pupa) | chicken, cockroach, grasshopper, dragonfly, frog |
| Four-stage | egg → larva → pupa → adult | butterfly, mosquito, mealworm beetle |
The recurring question: "Which group of organisms has a THREE-stage life cycle?" → the one WITHOUT a pupa (cockroach/grasshopper/frog). Mosquito & butterfly have a FOUR-stage life cycle. Always check for the word pupa.
- Mosquito: egg → larva → pupa → adult. Larvae live in water — so draining stagnant water stops breeding.
LIFE · 6 Plant Systems — Photosynthesis & Transport high frequency
The two tubes (memorise direction + cargo)
| Tube | Carries | Direction |
|---|---|---|
| Water-carrying tube | water and mineral salts | roots → up to leaves |
| Food-carrying tube | food / sugars made by photosynthesis | leaves → up and down to roots, fruits, flowers |
VERY IMPORTANT TO TAKE NOTE: "Substances are obtained from the water-carrying and food-carrying tubes of a plant on a SUNNY day. Which row is correct?" → Water-carrying tube = water + mineral salts; Food-carrying tube = sugars/food. (On a sunny day photosynthesis is active, so the food-carrying tube carries sugars.)
Photosynthesis — equation & conditions
- carbon dioxide + water →(light energy, chlorophyll)→ glucose (food) + oxygen
- Happens in the chloroplasts of green parts, needs light.
Day vs night: In daylight a plant takes IN CO₂ and gives OUT O₂ (photosynthesis > respiration). At night it only respires — takes in O₂, gives out CO₂. A "describe how the amount of CO₂ in the jar changed from 1 pm to 9 pm" question: the amount of CO₂ decreases when light is present, and increases when light is absent (after sunset).
Transpiration & stomata
- Stomata = tiny openings on leaves (mostly underside). They open WIDER in bright light / heat → more transpiration.
- Transpiration = loss of water vapour from leaves. The roots have to absorb more water, which will be transported through the water-carrying tubes to the leaves.
How it's asked: "State the function of the tiny openings found on leaves." → allow the exchange of gases and let water vapour ESCAPE (for photosynthesis & transpiration).
Roots
- Two functions: anchor the plant + absorb water and mineral salts (via root hairs).
LIFE · 7 Human Body Systems high frequency (Booklet B)
Digestive system — the order & what happens where
- Mouth → gullet → stomach → small intestine → large intestine → anus.
| Organ | Digestion? | Key job |
|---|---|---|
| Mouth | yes (teeth + saliva) | teeth breaks food into smaller pieces |
| Gullet | no | carries food to the stomach |
| Stomach | yes | breaks food into simpler substances |
| Small intestine | yes | absorbs digested food into the bloodstream |
| Large intestine | no | absorbs water from undigested food |
The recurring graph question: "Which graph shows the amount of undigested food leaving each organ?" → it DECREASES through mouth→stomach→small intestine (food being digested/absorbed), then the large intestine removes water so mass drops further. Small intestine = where absorption into the bloodstream happens.
Respiratory system
- Air path: nose → windpipe → lungs (air sacs).
- Gaseous exchange happens in the air sacs: O₂ is absorbed into the bloodstream, CO₂ is released from the bloodstream.
"S allows air to pass to and from T. Gaseous exchange with the bloodstream takes place at T." → S = windpipe, T = lungs (air sacs).
Skeletal & muscular
- The skeletal and muscular systems work together to enable movement.
LIFE · 8 Ecosystems, Food Webs & the Environment medium frequency
Food web roles (memorise definitions)
| Role | Definition |
|---|---|
| Producer | green plant — makes its own food (photosynthesis). ALWAYS at the start. |
| Primary consumer | eats producers (herbivore) |
| Predator / prey | An organism that is BOTH a predator and a prey eats another animal AND is eaten by one — e.g. a frog. |
| Decomposer | bacteria & fungi — breaks down dead matter into simpler substances, returns nutrients to soil |
"State the food producer(s)" → the green plant(s). "Which organism is both a prey and a predator?" → one that eats animals but is also eaten. When a new species M is introduced and Q falls while T rises, draw arrows: M eats Q (Q→M), and T eats M (M→T). Follow the population logic.
Adaptation — two types
| Type | Meaning | Example |
|---|---|---|
| Structural | a physical feature/characteristic | leaf insect looks like a leaf; bird beak shape |
| Behavioural | something the organism DOES | remaining motionless, swaying like leaves, migration |
The leaf-insect question (recurring): "similar to leaves" = structural; "remain motionless / sway" = behavioural. Purpose = to avoid being spotted by predators (camouflage), NOT to catch prey.
Deforestation & human impact
- Deforestation = cutting down / clearing forests.
- Effects: loss of animal habitat, more CO₂ in air (fewer plants to absorb it), soil erosion, reduced oxygen.
"State what deforestation is" + "effect on the gases in the surroundings": fewer trees → less photosynthesis → more carbon dioxide, less oxygen in the air. Always link cause → effect.
PHYS · 1 Matter, States & Materials highest frequency overall
The three states (memorise)
| State | Shape | Volume | Compressibility |
|---|---|---|---|
| Solid | definite shape | definite volume | cannot be compressed |
| Liquid | no definite shape | definite volume | cannot be compressed |
| Gas | no definite shape | no definite volume | can be compressed |
Material properties → matching to a use (VERY IMPORTANT TO TAKE NOTE)
- Tested properties: flexible, transparent/translucent/opaque, waterproof, strong, good/poor conductor of heat or electricity, magnetic.
"Which material is suitable for the face shield / bottle?" → match EVERY required property in the table (e.g. transparent + flexible + waterproof). Eliminate any option missing one.
Magnets
- Like poles repel, opposite poles attract. Only REPEL proves both are magnets — attraction can be magnet + magnetic material.
- A hanging bar magnet comes to rest pointing N–S. The part that attracts the most iron filings = the pole.
"Three steel bars X, Y, Z — which are magnets?" → use the repulsion test. If Z repels one end of a known magnet, Z is a magnet; attraction alone is inconclusive.
Measuring volume (Booklet B favourite)
- Solid that sinks: displacement — V = final water level − initial water level in the measuring cylinder.
- Object that FLOATS: push it fully under with a thin rod/sinker, or use a sinker tied to it; read the rise. Irregular solid → displacement (ruler won't work).
PHYS · 2 Light & Shadows high frequency
- Luminous objects give out their own light (Sun, lamp). Non-luminous are seen only because they reflect light.
- Light travels in a straight line → this is why shadows form when an object blocks the path.
| Type of material | Light passing through |
|---|---|
| Transparent | almost all — see clearly (CLEAR glass, CLEAR plastic) |
| Translucent | some — forms a light shadow (frosted glass, tracing paper) |
| Opaque | none — blocks ALL light and casts a DARK shadow (wood, metal) |
The diamond / "why can we see it" trap: A colourless, clear diamond is seen because light is reflected from it into our eyes — NOT because it is a light source. Same logic for the glass in a cupboard.
- Shadow size/length depends on the object's distance from the light: closer to the lamp = bigger shadow; as the Sun moves, a person's shadow changes length through the day (longest at sunrise/sunset).
PHYS · 3 Heat, Temperature & Changes of State high frequency
The five changes (memorise heat gain/loss)
| Change | From → To | Heat |
|---|---|---|
| Melting | solid → liquid | gains heat |
| Freezing | liquid → solid | loses heat |
| Boiling | liquid → gas (at 100 °C) | gains heat |
| Evaporation | liquid → gas (below boiling point, at surface only) | gains heat |
| Condensation | gas → liquid | loses heat |
Water boils at 100 °C and freezes/melts at 0 °C. "When water changes from liquid to gas at 100 °C, which is correct?" → the water is gaining heat (boiling). During a change of state the temperature STAYS CONSTANT even though heating continues — this flat part on a heating curve = melting or boiling.
Conductors vs insulators (of heat)
- Good conductors: metals (copper, aluminium, iron) — used for pans.
- Poor conductors / insulators: wood, plastic, air, foam, wool — used for handles, flasks, clothing. A double-walled bottle with an air gap keeps drinks hot/cold longer because air is a poor conductor.
"Why did she feel cold on the tiles but not the wooden floor?" → tiles are better conductors of heat, so they conduct heat away from her foot faster. "White fumes from an iron" = water vapour condensing into tiny water droplets (condensation); they vanish when the water droplets evaporate again.
PHYS · 4 Energy & Its Conversions high frequency (Booklet B)
- Kinetic energy = energy of motion. Potential energy = stored energy (from position or shape).
- The Sun is the ultimate source of almost all energy on Earth.
Energy conversions you must be able to name in a chain
| Situation | Conversion |
|---|---|
| Falling ball / object dropped from height | potential → kinetic (→ heat/sound on impact) |
| Compressed spring released | (elastic) potential → kinetic |
| Rubber-band toy car / boat | (elastic) potential in twisted band → kinetic |
| Battery-powered bulb | (chemical) potential → electrical → light + heat |
| Mobile phone ringing | (chemical) potential → electrical → sound (+ light) |
| Solar panel | light → electrical |
| Plant (photosynthesis) | light → (chemical) potential (food) |
The spring-on-the-ground question: compressed at A = potential energy stored; sliding at B = mostly kinetic; stopped at C = converted to heat + sound. "Which chart shows the energy at B?" → kinetic dominates.
- "Animals can be a source of energy" is TRUE (we get energy from food, including meat). "Plants are the direct source of energy for ALL animals" is FALSE — carnivores eat other animals.
PHYS · 5 Forces, Friction & Motion high frequency
Effects of a force (memorise all five)
A force can:
- move a stationary object,
- stop a moving object,
- speed up or slow down a moving object,
- change the direction of a moving object,
- change the shape (and size) of an object.
"Which is NOT a possible effect of a force?" → the answer is always change in MASS. Forces never change an object's mass — only its motion or shape.
The main forces
| Force | Key fact |
|---|---|
| Gravitational force | pulls objects downward toward Earth; acts on everything with mass, always present (even at the top of a swing); remains constant even when height above ground changes |
| Frictional force | opposes motion; between surfaces in contact. Reduced by wheels / ball bearings / lubrication. |
| Magnetic force | acts at a distance; like poles repel, opposite attract |
| Elastic spring force | a stretched/compressed spring pushes/pulls back to restore shape |
The cube-vs-ball on a slope question: the ball rolls further because it has less frictional force (rolling < sliding). Same mass → same gravitational force, so that's NOT the reason. "Did frictional and gravitational forces act at position B?" → usually YES to both.
- Springs: a stiffer spring stretches less under the same load. A stiffer spring, when stretched to the same length, will have more elastic spring force. A spring balance measures force in Newtons.
PHYS · 6 Electricity & Circuits very high frequency
Series vs parallel (the #1 circuit question)
| Series | Parallel | |
|---|---|---|
| Paths for current | one single path | more than one path (branches) |
| If one bulb fuses | all go out | others stay lit |
| Brightness with more bulbs | dimmer | same brightness as a single bulb |
"Connect the bulbs so that if one fuses, the other still lights" → draw them in PARALLEL. "In which circuits will bulb G have the same brightness?" → compare number of batteries & whether bulbs share a branch. More batteries = brighter; series adds dimming.
Circuit basics
- A working circuit needs: a source (battery), a complete path, and a bulb. A switch OPEN breaks the circuit → no current.
- A battery in a circuit must be connected + to − for current to flow. Mark the positive terminal with '+'.
Electromagnets (Booklet B favourite)
- Made by winding wire around an iron core and passing current through it. Magnetism appears ONLY while current flows.
- Stronger electromagnet: more coils of wire, or a larger current (more batteries connected in series).
- Used in: electric bells, motors, speakers, scrap-yard cranes.
"The fixed iron bar could just carry an iron block… suggest changes to increase magnetic strength" → increase current (add more batteries) or add more coils → stronger electromagnet → lifts the block higher / with more force.
PHYS · 7 The Water Cycle medium frequency
- Ocean/lake →(evaporation, Sun heats)→ water vapour in air →(condensation high up)→ clouds →(precipitation)→ rain/snow back to land & sea.
| Process | What happens | Heat |
|---|---|---|
| Evaporation | liquid water → water vapour (from sea, lakes, soil, plants) | gains heat |
| Condensation | water vapour → tiny water droplets forming clouds | loses heat |
| Precipitation | rain, snow, hail falls to Earth | — |
"How did the students obtain fresh water at the beach?" → evaporation of seawater (Sun) then condensation on a cool surface, collected as water droplets — a mini water cycle. Name BOTH processes.
TECH · 1 Experiment Design (the highest-value skill) every Booklet B has one
The three variables — label them correctly
| Type | Also called | You… |
|---|---|---|
| Manipulated | changed variable | deliberately change (ONE only) |
| Responding | measured variable | measure / observe the result of |
| Controlled | kept constant | keep the SAME in every set-up (everything else) |
The golden rule: change ONLY ONE variable at a time. A fair test keeps all other conditions identical. If a question asks "what should set-up B be?", it must differ from A in EXACTLY the manipulated variable and nothing else (same fruit, same number, same container).
Control experiment
- The control is the set-up with NO treatment / the normal condition, used for comparison. E.g. testing a repellent → the control set-up has NO repellent applied.
Reliability & accuracy
- Repeat the experiment several times and take an average → more reliable.
- Use correct apparatus / read at eye level → more accurate.
How it's asked (recurring): "State how to carry out a control experiment" → describe the identical set-up with the variable removed. "Suggest one way to make the result more reliable" → repeat and average / use more trials.
TECH · 2 The Recurring Traps — read these last mark-killers
- "ALL living things" → only reproduction is universal. Not "make food", not "move by themselves".
- Three-stage life cycle = NO pupa (cockroach/grasshopper). Mosquito & butterfly have a four-stage life cycle.
- Pollination ≠ fertilisation. Pollination = pollen grain lands on the stigma. Fertilisation = male reproductive cell fuses with female reproductive cell in the ovule → zygote. Seeds need fertilisation, not just pollination.
- Fertilisation in humans happens in the fallopian tube; the fertilised egg develops in the womb.
- We see non-luminous objects because they REFLECT light — not because they glow.
- A force never changes mass. It changes motion or shape. "NOT an effect of a force" = change in mass.
- During a change of state, temperature stays constant (the flat part of the heating curve).
- Boiling/evaporation = gaining heat. "Liquid to gas at 100 °C" → gaining heat, not losing.
- Parallel circuit: one bulb fuses, others stay lit. Series: all go out.
- Attraction alone does NOT prove a magnet — only repulsion does (magnet can attract a magnetic material).
- Water-carrying tubes carry water + mineral salts UP to the leaves; food-carrying tubes carry food/sugars up and down (to roots, fruits, flowers). On a sunny day the food-carrying tube carries sugars.
- Day vs night gaseous exchange: daytime plant takes in CO₂ / gives out O₂; at night the reverse.
- Deforestation → more CO₂, less oxygen (fewer plants to photosynthesise).
Answering structured questions: always give cause → effect, not just a label. "The ball rolled further because it had less frictional force acting on it" scores; "less friction" alone may not. Name the process AND explain what happens.