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Science lesson plan · 2nd grade (Year 3 in England) · 30 minutes

Heating and cooling: can the change be undone?

States of matter

CCSS NGSS.2-PS1-4England: KS1 Y2 Uses of everyday materialsEngland: KS2 Y5 Properties and changes of materials

Objective and success criteria

Students will: Heating and cooling: can the change be undone?.

  • I can answer questions on today's skill on my own, without help.
  • I can explain each step and say why it works.
  • I can check my answer and spot a mistake.

Before and after

Needs first: Melting, freezing, evaporating and condensing

Leads to: What happens when we heat it?; What happens when we cool it?

Materials: Ice, water and a kettle (teacher demo), Particle diagrams, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).

Warm-up · 4 min

  • Quick retrieval from earlier learning (Melting, freezing, evaporating and condensing). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. Which change of state is this: butter softening into a puddle in a hot pan? (melting / freezing / evaporating / condensing) → meltingPrompt: What state does it start in, and what state does it end in?
  2. What is the name for a change from solid to liquid? (evaporating (or boiling) / freezing / condensing / melting) → meltingPrompt: Heating makes solids melt and liquids evaporate.
  3. Changes of state: which statement is true? (Melting makes a substance lose mass. / Water only evaporates when it boils. / The water on the outside of a cold can leaks through the metal. / Steam (water vapour) is invisible; the white cloud above a kettle is tiny water droplets.) → Steam (water vapour) is invisible; the white cloud above a kettle is tiny water droplets.Prompt: Where does the water on a cold can come from?

Hook · 3 min

  • Show an ice cube melting and a kettle steaming and ask what is the same and what is different.
  • Share the objective: Heating and cooling: can the change be undone?. Read the success criteria together.

I do: model it · 7 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: Can this change be undone: frying an egg?
  • Step 1: Cooking and burning make new materials that cannot be turned back.
  • Step 2: So the answer is: cannot change back
  • Answer: cannot change back
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 6 min

  • Do these together. Students try each step on whiteboards before you reveal it.
  • Use the hints as prompts rather than giving the answer.
  1. Can this change be undone: an ice lolly (popsicle) melting? (can change back / cannot change back) → can change backPrompt: Could you get the starting material back by warming it or cooling it?
  2. Three of these changes CANNOT be undone. Which one is different? (an ice lolly (popsicle) melting / baking a cake / popping popcorn / burning a log on a fire) → an ice lolly (popsicle) meltingPrompt: Think about melting and freezing versus cooking and burning.

You do: independent practice · 7 min

  • Students work on the student sheet. Circulate and check the first two answers of every student early.
  • Students who finish: write a question of their own for a partner, with the answer.

The 6 questions are on the student sheet below, with answers in the key.

Exit ticket · 3 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. Can this change be undone: toasting bread? (can change back / cannot change back) → cannot change backPrompt: Could you get the starting material back by warming it or cooling it?
  2. Can you turn a fried egg back into a raw egg by putting it in the fridge? (Yes, if you wait a day. / Yes, but only for brown eggs. / No, cooking made a change that cannot be undone. / Yes, cooling always undoes heating.) → No, cooking made a change that cannot be undone.Prompt: Is a cooked egg white still see-through and runny?

Watch out for

  • Everyday meanings of words getting in the way of the science meaning: define key words explicitly.
  • Remembering facts without the reason: ask "why?" and "what is the evidence?"

Support and stretch

Support

  • Review first: Melting, freezing, evaporating and condensing.
  • Use concrete materials: ice, water and a kettle (teacher demo).
  • Give the first step of each question, or a partly worked example to finish.
  • Pair with a confident partner for the guided practice.

Stretch

  • Move on to: What happens when we heat it?; What happens when we cool it?.
  • Explain a common mistake in writing and how to fix it.
  • Write a word problem that uses today's skill, then solve a partner's.

Homework and more practice

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-2.

Free lesson plan from eurekami.com/lesson-plan-builder

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Heating and cooling: can the change be undone?

Name

Date

Score/ 6

  1. Question 1

    Can this change be undone: burning a log on a fire?

    • A. can change back
    • B. cannot change back

  2. Question 2

    Three of these changes CANNOT be undone. Which one is different?

    • A. frying an egg
    • B. baking a cake
    • C. toasting bread
    • D. water freezing into ice cubes

  3. Question 3

    Ice cream is left in the sun and melts. Then it is put back in the freezer. Is it the same as before?

    • A. It freezes solid again, though it may be icier and harder than before.
    • B. It stays a liquid in the freezer.
    • C. It burns.
    • D. It turns into milk powder.

  4. Question 4

    Can this change be undone: candle wax melting?

    • A. can change back
    • B. cannot change back

  5. Question 5

    Melted chocolate is poured into a mould and put in the fridge. What happens?

    • A. It turns into water.
    • B. It turns solid again, in the mould's shape.
    • C. It stays liquid for ever.
    • D. It turns into cake.

  6. Question 6

    Can this change be undone: water freezing into ice cubes?

    • A. can change back
    • B. cannot change back

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Answer key: Heating and cooling: can the change be undone?

  1. 1. B. cannot change back

  2. 2. D. water freezing into ice cubes

  3. 3. A. It freezes solid again, though it may be icier and harder than before.

  4. 4. A. can change back

  5. 5. B. It turns solid again, in the mould's shape.

  6. 6. A. can change back