Why does my child lose marks in PSLE Science even when the idea is correct?

PSLE Science markers award marks for precise scientific language, not just the general idea. A student who writes 'the water disappeared' instead of 'the water evaporated' may lose the mark even if they understand the concept. Markers follow a mark scheme that lists specific accepted keywords and phrases. Using everyday language instead of scientific terminology is one of the most common reasons students lose marks in Booklet B open-ended questions.

What are PSLE Science keywords?

PSLE Science keywords are the precise scientific terms and phrases that examiners look for in open-ended answers. They include topic-specific vocabulary such as 'evaporation', 'heat energy', 'photosynthesis', and 'gravitational force', as well as cause-and-effect linking phrases such as 'as a result', 'therefore', and 'due to'. Using the correct keyword shows the marker that the student understands the concept scientifically, not just in everyday language.

Do PSLE Science keywords differ by topic?

Yes. PSLE Science is organised into five themes: Diversity, Cycles, Systems, Interactions, and Energy. Each theme has its own set of expected keywords. For example, the Cycles theme requires terms like 'condensation', 'evaporation', 'water vapour', and 'precipitation'. The Energy theme requires terms like 'heat energy', 'energy conversion', 'conductor', and 'insulator'. Students should build a keyword bank for each theme rather than trying to memorise a single generic list.

What are PSLE Science command words and why do they matter?

Command words are the instruction words in a question, such as 'state', 'explain', 'compare', 'predict', and 'suggest'. Each command word requires a different type of answer. 'State' needs a short direct answer. 'Explain' requires a cause-and-effect link using scientific reasoning. 'Compare' must mention both items and use comparison language such as 'more than', 'higher than', or 'unlike'. Missing the command word requirement is one of the top reasons for losing marks even when the student knows the science.

How can parents help children practise PSLE Science keywords at home?

Use the say-this-not-that approach: whenever your child gives a vague answer at home, ask them to replace the non-scientific word with the correct term. For example, if they say 'the ice melted faster', ask 'what energy caused that?' to prompt 'heat energy was absorbed'. Spending 10 minutes per week on keyword replacement practice is more effective than doing extra papers.

How does the 2023 syllabus cover cells in PSLE Science?

The official MOE 2023 Primary Science Syllabus places the learning outcome ‘recognise that a cell is a basic unit of life’ under Cycles in Plants and Animals (Reproduction). The syllabus does not establish a separate standalone Cells topic in that section. For the complete 2026 examination scope, check the official SEAB PSLE Science syllabus.

PSLE Science Language Guide

PSLE Science Keywords: Precision Language That Earns Marks

Last reviewed: August 2026 · By: PSLE Hero Editorial Team · Aligned to the MOE 2023 Primary Science Syllabus (first examined 2026)

One of the most common PSLE Science frustrations: your child understands the concept but still loses marks. The reason is almost always the same — vague, non-scientific language. This guide explains exactly which keywords markers look for, topic by topic, across all five PSLE Science themes.

Quick answer: PSLE Science markers follow a mark scheme that lists specific accepted keywords. Writing "the water disappeared" instead of "the water evaporated" loses the mark — even if the idea is correct. Precision language is not optional: it is the difference between 1 mark and 0.

Why Keywords Matter in PSLE Science

PSLE Science Booklet B open-ended questions are worth 40 marks. Markers award marks point-by-point using an internal mark scheme. Each mark is tied to a specific scientific concept expressed in correct scientific language.

When a student writes in everyday language — "the plant made food", "things got hot", "the magnet pushed the other magnet away" — the examiner cannot confirm precise conceptual understanding. The mark may be withheld.

When the same student writes — "the plant produced glucose through photosynthesis", "heat energy was transferred to the object", "the magnets repelled because their like poles faced each other" — each scientific term signals that the student truly understands the underlying science.

Important: This guide uses vocabulary aligned to the MOE 2023 Primary Science Syllabus. Always verify against the official SEAB PSLE formats page for the current scope of examination topics.

Step 1: Decode the Command Word First

Before reaching for any keyword, your child must identify the command word in the question. The command word defines what type of answer is needed. Answering with the wrong structure loses marks regardless of which keywords are used.

State / Name / Identify

Short, direct answer only. No explanation needed. One or two scientific terms are usually sufficient.

Explain / Why / How

Cause-and-effect answer required. Use "because", "as a result", "therefore". This is where keywords matter most.

Compare

Must mention both items. Use "more than", "faster than", "higher rate of", "unlike". Never describe only one side.

Predict

State what will happen next, then briefly explain using scientific reasoning — one or two sentences.

Suggest

Propose a reason, variable, or improvement. The answer must be scientifically plausible.

Describe

Explain what is observed. Refer to specific details from the diagram, table, or graph provided.

The Five PSLE Science Themes: Keyword Banks

PSLE Science is organised around five themes. Every question belongs to one of these themes. Below are the essential keywords for each theme, with precision vocabulary that earns higher marks highlighted separately.

🌿 Theme 1: Diversity

Living and non-living things, characteristics of living things, classification of animals, plants, and materials.

Essential Keywords

living thing non-living thing organism characteristic reproduce respond to stimuli respire / breathe excrete grow move vertebrate / invertebrate mammal / reptile / amphibian / fish / bird flowering / non-flowering plant

Precision Keywords (for Explain / Compare questions)

adaptation structural adaptation habitat classify / classification property / properties conductor / insulator (materials) transparent / opaque / translucent soluble / insoluble permeable / impermeable

❌ Loses marks		✓ Earns marks
The fish has gills to breathe underwater	→	The fish has gills as a structural adaptation to absorb dissolved oxygen from water
The cactus stores water in its trunk	→	The cactus has a thick, fleshy stem as a structural adaptation to store water in its dry desert habitat
The material lets light through a bit	→	The material is translucent — it allows some light to pass through but not enough to see clearly through it

💧 Theme 2: Cycles

The water cycle, changes of state, life cycles of plants and animals, and reproduction.

Essential Keywords

evaporation condensation precipitation water vapour water cycle solid / liquid / gas melting freezing boiling change of state life cycle germination pollination fertilisation seed dispersal

Precision Keywords

rate of evaporation surface area humidity heat energy absorbed / released sexual / asexual reproduction complete / incomplete metamorphosis

❌ Loses marks		✓ Earns marks
The water disappeared from the dish	→	The water evaporated — it changed from liquid to water vapour
Water on the cold glass came from the air	→	Water vapour in the surrounding air condensed on the cold glass surface, forming water droplets
Wet clothes dried faster on a windy day	→	The rate of evaporation increased on a windy day because wind removed water vapour above the wet clothes, allowing more water molecules to evaporate
The ice became water	→	The ice melted — it changed from solid to liquid as heat energy was absorbed from the surroundings

🧠 Theme 3: Systems

Plant systems (parts and functions), human systems (digestive, respiratory, circulatory), and electrical systems.

Essential Keywords — Plant System

root stem leaf flower absorb water and minerals transport water photosynthesis chlorophyll glucose starch carbon dioxide oxygen sunlight transpiration

Essential Keywords — Human Systems

digestion nutrients absorbed into the bloodstream oesophagus stomach small intestine large intestine respiration trachea / bronchi / lungs / alveoli gas exchange heart arteries / veins / capillaries pump blood circulate / circulation

Essential Keywords — Electrical System

complete circuit switch (open / closed) conductor insulator series circuit parallel circuit battery / cell current brightness / loudness (effect)

❌ Loses marks		✓ Earns marks
Plants make food using sunlight	→	Plants use sunlight, carbon dioxide, and water to produce glucose through photosynthesis. Chlorophyll in the leaves absorbs sunlight for this process
Food is broken down so the body can use it	→	Food is digested in the stomach and small intestine. Nutrients are absorbed through the walls of the small intestine into the bloodstream
The bulb is dim because there are more bulbs	→	In a series circuit, adding more bulbs increases the total resistance, which reduces the current. Each bulb therefore glows less brightly
The switch stopped the light	→	Opening the switch broke the circuit, stopping the flow of current and causing the bulb to go out

🔗 Theme 4: Interactions

Forces (gravitational, magnetic, frictional, elastic), magnets, food chains and webs, ecosystems.

Essential Keywords — Forces and Magnets

force gravitational force weight frictional force / friction magnetic force elastic force attract / repel like poles repel unlike poles attract north pole / south pole magnetised / demagnetised

Essential Keywords — Food Chains and Webs

producer primary consumer / secondary consumer predator / prey food chain food web ecosystem population decomposer

❌ Loses marks		✓ Earns marks
The two magnets pushed each other away	→	The two magnets repelled each other because their like poles (both north or both south) faced each other
Friction made it harder to slide the box	→	Frictional force between the box and the surface opposed the motion of the box, making it harder to slide
The grass feeds the rabbit	→	The grass is the producer in this food chain. The rabbit is a primary consumer that feeds on the grass
If the fox dies, there will be more rabbits	→	If the fox population decreases, fewer rabbits would be eaten by predators. The rabbit population would therefore increase

⚡ Theme 5: Energy

Forms of energy (heat, light, sound, kinetic, potential), energy conversion, heat transfer, and energy from food and fuels.

Essential Keywords

heat energy light energy sound energy kinetic energy potential energy energy conversion heat source conductor of heat insulator of heat conduction convection radiation absorbed emitted / released temperature

Precision Keywords

rate of heat transfer thermal conductor / thermal insulator dark / dull surface (absorbs / emits more) light / shiny surface (absorbs / emits less) gravitational potential energy stored energy / released energy

❌ Loses marks		✓ Earns marks
The metal spoon got hot	→	Heat energy was conducted along the metal spoon from the hot end to the cool end, because metal is a good conductor of heat
The dark can cooled down faster	→	The dark, dull surface of the can emitted heat energy more quickly through radiation than a light, shiny surface would
The ball at the top has energy	→	The ball at the top of the ramp has gravitational potential energy due to its height above the ground
The battery makes the motor move	→	The battery converts chemical energy into electrical energy. The motor then converts electrical energy into kinetic energy

Linking Phrases That Connect Keywords Into Arguments

Individual keywords only earn marks when they are joined logically. Examiners look for cause-and-effect reasoning. These linking phrases signal that your child understands why something happens, not just what happened.

because as a result therefore which causes due to this allows so that which means more than / less than faster than / slower than higher rate of / lower rate of unlike / in contrast

Worked Examples: Keywords in a Full Answer

Question (2 marks): A student places a copper rod and a wooden stick into a cup of hot water. After five minutes, the copper rod feels hotter to touch than the wooden stick. Explain why.

✗ Weak answer — likely 0 to 1 mark

Copper is metal and it gets hot faster. Wood does not get as hot because it does not let heat through as well.

✓ Strong answer — 2 marks

Copper is a good conductor of heat. Heat energy from the hot water is conducted along the copper rod quickly to the part held by the student. Wood is a heat insulator, so very little heat energy is transferred along the wooden stick. As a result, the copper rod feels much hotter to the touch.

Question (2 marks): Describe how water returns from the land to the atmosphere in the water cycle.

✗ Weak answer — likely 0 to 1 mark

Water on the ground dries up and goes into the air. This happens when it is hot outside.

✓ Strong answer — 2 marks

Water on the land's surface undergoes evaporation when exposed to heat energy from the sun. The water changes from liquid into water vapour, which rises into the atmosphere. When water vapour cools at higher altitudes, it undergoes condensation and forms clouds.

Parent Practice Checklist

Use this checklist when your child completes any open-ended Science question at home.

Did my child identify the command word (State / Explain / Compare / Predict) before writing?
Did the answer use the specific scientific term, not an everyday substitute? (e.g. "evaporation" not "water dried up")
For Explain questions: is there a clear cause-and-effect link using "because", "as a result", or "therefore"?
For Compare questions: did the answer mention both items and use comparison language ("more than", "faster than", "unlike")?
Did the answer refer to specific details in the question — the object name, diagram label, or table value?
Is the answer the right length? (2 marks means 2 clear science points; 4 marks means 4 points)
Are there any vague words — "things", "it", "faster", "better" — that can be replaced with precise scientific terms?

Note on Cells (PSLE 2026 onward): The official MOE 2023 Primary Science Syllabus places the learning outcome “recognise that a cell is a basic unit of life” under Cycles in Plants and Animals (Reproduction). It does not present a separate standalone Cells topic in that section. For the complete 2026 examination scope, check the official SEAB PSLE formats page.

Related Science Guides

Keywords are the building blocks. These guides show you how to use them inside a structured answer:

PSLE Science CER Answering Technique — how to structure a complete open-ended answer using Claim, Evidence, and Reasoning
How to Answer PSLE Science Open-Ended Questions — question types, step-by-step approach, and worked examples
PSLE Science Experimental Questions Guide — fair tests, variables, and observation questions
PSLE Science Revision Tips — full preparation guide for P5 and P6

Build keyword habit through daily practice

Reading keyword lists helps, but writing answers with those keywords is what builds the exam habit. Use structured practice questions to test whether your child reaches for scientific terms automatically — or falls back on everyday language under exam pressure.

Try free PSLE Science practice questions →

Sources: MOE Primary Science Curriculum & Syllabus · SEAB PSLE Subject Information Sheets