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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: a bathroom mirror steaming up? (melting / freezing / evaporating / condensing) → condensingPrompt: What state does it start in, and what state does it end in?
  2. What is the name for a change from liquid to solid? (condensing / freezing / melting / evaporating (or boiling)) → freezingPrompt: Heating makes solids melt and liquids evaporate.
  3. Changes of state: which statement is true? (Water evaporates faster on a warm, windy day. / The water on the outside of a cold can leaks through the metal. / Water only evaporates when it boils. / Melting makes a substance lose mass.) → Water evaporates faster on a warm, windy day.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: baking a cake? (can change back / cannot change back) → cannot 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? (toasting bread / baking a cake / chocolate melting in a warm hand / frying an egg) → chocolate melting in a warm handPrompt: 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. Melted chocolate is poured into a mould and put in the fridge. What happens? (It turns into water. / It turns solid again, in the mould's shape. / It turns into cake. / It stays liquid for ever.) → It turns solid again, in the mould's shape.Prompt: Melting can be reversed by cooling.
  2. Three of these changes CANNOT be undone. Which one is different? (toasting bread / burning a log on a fire / popping popcorn / candle wax melting) → candle wax meltingPrompt: Think about melting and freezing versus cooking and burning.

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: popping popcorn?

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

  2. Question 2

    Three of these changes CAN be undone. Which one is different?

    • A. chocolate melting in a warm hand
    • B. an ice lolly (popsicle) melting
    • C. water freezing into ice cubes
    • D. baking a cake

  3. Question 3

    Can you turn a fried egg back into a raw egg by putting it in the fridge?

    • A. Yes, but only for brown eggs.
    • B. No, cooking made a change that cannot be undone.
    • C. Yes, cooling always undoes heating.
    • D. Yes, if you wait a day.

  4. Question 4

    Can this change be undone: chocolate melting in a warm hand?

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

  5. Question 5

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

    • A. toasting bread
    • B. burning a log on a fire
    • C. frying an egg
    • D. chocolate melting in a warm hand

  6. Question 6

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

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

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

  1. 1. B. cannot change back

  2. 2. D. baking a cake

  3. 3. B. No, cooking made a change that cannot be undone.

  4. 4. A. can change back

  5. 5. D. chocolate melting in a warm hand

  6. 6. C. It turns solid again, in the mould's shape.