Last reviewed: 2 November 2026
Updated November 2026. These Grade 6 notes on matter cover both sub-strands of Strand 2.0 in Grade 6 Science and Technology: change of state (melting, freezing, evaporation, condensation, sublimation and deposition, and where we use them) and composition of air (the gases in air, their uses, the burning candle experiment, and air pollution). Each part has a home activity and practice questions with answers.
The topics and projects follow the Matter strand of the KICD Grade 6 Science and Technology curriculum design, which gives Change of State about 18 lessons and Composition of Air about 16.
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Grade 6 Notes on Matter: States of Matter Recap
Matter is anything that has mass and occupies space. It exists in three states:
- Solids have a fixed shape and a fixed volume (stone, ice, wax).
- Liquids have a fixed volume but take the shape of their container (water, milk, cooking oil).
- Gases have no fixed shape or volume and spread out to fill any space (air, steam).
Change of State: Heating and Cooling
Heating or cooling a substance can change its state. The six changes in the Grade 6 design are:
| Change | From → to | Heating or cooling? | Example |
|---|---|---|---|
| Melting | Solid → liquid | Heating | Ice turning to water; candle wax near the flame |
| Freezing | Liquid → solid | Cooling | Water turning to ice in a freezer |
| Evaporation | Liquid → gas | Heating | Wet clothes drying; a puddle disappearing in the sun |
| Condensation | Gas → liquid | Cooling | Water drops on the lid of a cooking pot; dew on grass |
| Sublimation | Solid → gas directly | Heating | Naphthalene balls (moth balls) slowly disappearing in a wardrobe; dry ice |
| Deposition | Gas → solid directly | Cooling | Frost forming on very cold surfaces |
Activity: put an ice cube on a saucer in the sun and watch it melt, then leave the water to evaporate. Hold a cold, dry glass over a cup of hot tea and see the condensation. Always have an adult present when heating substances, and keep away from open flames to avoid burns and fires.
Uses of Change of State in Everyday Life
- Making candles: old wax or beeswax is melted, poured into a mould with a wick and left to freeze (solidify). This is one of the two projects in the design.
- Repairing plastic: a crack in a plastic basin or jerrycan can be sealed by gently melting the plastic so it joins as it cools, the design’s second project. Do this only with an adult, in open air, because burning plastic gives off harmful smoke.
- Drying clothes, grains and fish uses evaporation.
- Making ice and ice lollies uses freezing.
- Distilling water uses evaporation followed by condensation.
- Welding and casting metals use melting and freezing.
Composition of Air
Air is a mixture of gases. In dry air the proportions are roughly:
| Gas | Approximate share of air |
|---|---|
| Nitrogen | 78% |
| Oxygen | 21% |
| Argon and other noble gases | Just under 1% |
| Carbon dioxide | About 0.04% |
Air also carries varying amounts of water vapour, plus dust and smoke particles. The design asks learners to draw these figures as a pie chart: nitrogen takes up about 281° of the circle (78% of 360°) and oxygen about 76° (21% of 360°).
Activity: Oxygen in air and the burning candle
- Fix a short candle upright in a shallow dish and light it (with an adult).
- Cover it with an upside-down glass jar.
- Watch: the flame grows dim and goes out after a short time.
Conclusion: the candle needs oxygen to burn. Once the oxygen in the jar has been used up, the flame goes out. This shows that oxygen is one of the components of air.
Uses of the gases in air
- Oxygen: needed by people, animals and plants for breathing; used in hospitals for patients with breathing problems; needed for burning.
- Nitrogen: used by plants to make proteins (it reaches them through the soil); used to make fertilisers; used in food packaging to keep food fresh.
- Carbon dioxide: used by green plants to make food (photosynthesis); used in some fire extinguishers and in fizzy drinks.
- Argon: used inside some electric bulbs.
Air Pollution and How to Reduce It
Air pollution is the presence of harmful substances in the air. Common pollutants include smoke from burning rubbish, charcoal and firewood; fumes from vehicles and factories; dust from roads and quarries; and sprays used on farms.
Effects: coughing, chest and eye problems; dirty buildings and clothes; harm to plants and animals; and contribution to climate change.
Ways to reduce it: plant and care for trees, avoid burning rubbish and plastics, use clean energy such as solar and improved jikos, service vehicles, and water dusty roads or grounds. Wear dust masks or goggles where the air is dusty or smoky, as the design advises. A class project in the design is making posters on air pollutants and how to control them.
Practice Questions With Answers
- Name the change of state when water drops form on a cold glass. Answer: condensation.
- Moth balls in a wardrobe get smaller without melting. What change is this? Answer: sublimation.
- Which gas makes up the largest part of air? Answer: nitrogen (about 78%).
- Why does a candle covered with a jar go out? Answer: it uses up the oxygen in the jar, and oxygen is needed for burning.
- Give two ways of reducing air pollution at school. Answer: any two of planting trees, not burning rubbish, watering dusty grounds, using clean energy.
More Grade 6 Science
Matter is Strand 2.0 of Grade 6 Science and Technology. See every strand in the Grade 6 Science and Technology notes and read the Grade 6 notes on fungi. Grade 6 ends with KPSEA, and the KNEC 2026 KPSEA timetable allowed 1 hour 40 minutes for Integrated Science.
Practise free on the Grade 6 CBC Challenge, try a KPSEA Grade 6 Integrated Science practice paper, or open the Grade 6 notes hub.
Frequently Asked Questions
What are the changes of state in Grade 6?
Melting, freezing, evaporation, condensation, sublimation and deposition. Heating causes melting, evaporation and sublimation; cooling causes freezing, condensation and deposition.
What is the composition of air?
About 78% nitrogen, 21% oxygen, just under 1% argon and other noble gases, and about 0.04% carbon dioxide, plus water vapour and dust.
What is sublimation? Give an example.
Sublimation is when a solid changes straight into a gas without becoming a liquid first. Moth balls (naphthalene) getting smaller in a wardrobe is an example.
How can we reduce air pollution?
Plant trees, avoid burning rubbish and plastics, use cleaner energy such as solar, service vehicles, and water dusty grounds.
Want marked practice? The first five questions of each paper are free. A Day Pass (KSh 20) unlocks the full Grade 6 Integrated Science papers with worked answers for a day, and the Monthly Pass (KSh 500) opens every grade and subject for a month. Compare passes.