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Topic ladders · Chemistry

States of Matter & Changes

One topic, four rungs: from Classes 1–3 to Classes 11–12. Start at your own stage, or climb from the bottom. Every rung follows the same six steps: Notice, Guess, Try, Observe, Explain, Ask another question.

Print the family table: all four rungs side by side on one sheet, so everyone at home can find their own rung.

Choose your class stage

Rung 1 · Classes 1–3

Solid, Liquid, Gas

Before you start: safety and help

For the grown-up who helps.

  • Safety: Wipe any water spills immediately so no one slips. Blow up the balloon yourself, and pick up any burst balloon pieces straight away: they are a choking risk for small children.
  • Good questions: "Does it keep its shape?"

What you need

  • Ice cubes, water, a balloon or an empty plastic bottle
  • Different solid objects
  • Cups and bowls of different shapes

Child steps

  1. Notice. Look at ice, water, and the air around you. How are they different?
  2. Guess. What will happen to an ice cube if left in a warm place? Can you hold air?
  3. Try. Watch ice melting. Pour water into different containers. Feel air by squeezing an empty bottle near your cheek, or by letting air out of a balloon.
  4. Observe. Which materials keep their shape? Which take the shape of the container? Which spread out to fill the space?
  5. Explain. Tell someone the differences between solid, liquid and gas.
  6. Ask another question. Can a substance change from one state to another? How?
For teachers
  • Learning aims: Identify the three states of matter through observation of properties.
  • Key vocabulary: solid, liquid, gas, shape, flow, melt.
  • Review: Children give one example of each state and one property.

Rung 2 · Classes 4–7

Melting, Freezing, Evaporation and Condensation

Before you start: safety and help

For the grown-up or teacher who helps. Students: read it too, so you know the rules.

  • Safety: Use warm water, never boiling: steam burns. If any heating is used, a grown-up does it.

What you need

  • Ice, water, a small plate, an ice tray or small cup
  • Mirror or cold steel spoon
  • A cup of warm water (poured by a grown-up)
  • Optional: salt

Student steps

  1. Notice. Water can be solid, liquid or gas. Where do you see these changes in daily life?
  2. Guess. What makes ice melt? What makes water disappear from a wet cloth? What makes droplets appear on a cold surface?
  3. Try. Leave ice on a plate to melt. Put a little water in the freezer. Leave a spoonful of water on a plate in a warm, sunny place. Hold a cold spoon or mirror above a cup of warm water.
  4. Observe. Record what happens in each case and how long it takes.
  5. Explain. Name the changes (melting, freezing, evaporation, condensation) and say what causes them (heating or cooling).
  6. Ask another question. How does salt affect the melting of ice? Where do we see the water cycle in nature?
For teachers
  • Learning aims: Observe and name changes of state; link them to temperature and the water cycle.
  • Key vocabulary: melting, freezing, evaporation, condensation, temperature.
  • Answer to step 6: ice sprinkled with salt melts faster, and the salty mixture becomes colder than plain ice. Salt lowers the temperature at which ice melts. This is why salt is put on icy roads in cold countries.
  • Review: Students describe one change of state they observed and its reverse.

Rung 3 · Classes 8–10

Physical and Chemical Changes

Before you start: safety and help

For the grown-up or teacher who helps. Students: read it too, so you know the rules.

  • Safety: Burning is a grown-up demonstration only: outdoors, away from anything that can catch fire, with a bucket of water ready. Students watch from a distance and do not handle matches. Keep vinegar away from eyes; the vinegar–baking soda fizz can splash, so keep faces back.

What you need

  • Paper, salt, water, vinegar, baking soda, a steel spoon, a glass
  • For the grown-up demonstration only: a matchbox, a steel plate, a bucket of water
  • Notebook

Student steps

  1. Notice. Some changes are easy to reverse; others produce new substances.
  2. Guess. Which of these are physical changes and which are chemical: tearing paper, burning paper, dissolving salt, mixing vinegar and baking soda?
  3. Try. Tear paper. Dissolve salt in water. Add a spoon of baking soda to a little vinegar in a glass. Watch a grown-up burn a small piece of paper on a steel plate outdoors.
  4. Observe. Look for new substances, heat, gas (bubbles), colour change, smell, or whether you can get the starting material back.
  5. Explain. Classify each change and give reasons based on evidence.
  6. Ask another question. How can we decide if a change is chemical when it is not obvious?
For teachers
  • Learning aims: Distinguish physical and chemical changes using observable evidence.
  • Key vocabulary: physical change, chemical change, reversible, irreversible, new substance, reaction.
  • Note: "Cannot be reversed" is a clue, not a rule. Breaking a glass cannot be undone but is a physical change (still glass). Dissolved salt can be got back by evaporation, so dissolving is physical. The best evidence of a chemical change is a new substance (the gas from vinegar and baking soda is carbon dioxide; burning makes ash, smoke and gases).
  • Review: Students present one physical and one chemical change with evidence.

Rung 4 · Classes 11–12

Investigating Rates of Reaction

Before you start: safety and help

For the grown-up or teacher who helps. Students: read it too, so you know the rules.

  • Safety: School laboratory only, with a teacher and the school's safety rules; not a home activity. Goggles on throughout. Magnesium and acid gives off hydrogen, which burns: no flames nearby. Thiosulfate and acid gives off sulfur dioxide, which irritates the lungs: use small amounts, a well-aired room, and extra care for students with asthma. Warm solutions gently in a water bath, not over a flame.

What you need

  • School laboratory only: dilute acid and magnesium ribbon, or sodium thiosulfate solution and dilute hydrochloric acid (the "disappearing cross" test), at the strengths the school uses
  • Measuring cylinder, stopwatch, thermometer, gas syringe or upturned measuring cylinder, safety goggles

Student steps

  1. Notice. Chemical reactions happen at different speeds.
  2. Guess / Hypothesise. How do concentration, temperature, surface area or a catalyst affect the rate?
  3. Try. Design and perform a controlled experiment measuring rate under different conditions (change one factor at a time).
  4. Observe. Collect quantitative data (time, volume of gas, time for a cross to disappear, etc.) and plot graphs.
  5. Explain. Interpret the results using collision theory and discuss experimental errors.
  6. Ask another question. How is control of reaction rate important in industry or biological systems?
For teachers
  • Learning aims: Investigate factors affecting rate of reaction; apply collision theory; handle quantitative data safely.
  • Review: Students present graphs, conclusions and evaluation of method.

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