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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: drops forming on a cold can taken from the fridge? (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 solid to liquid? (melting / condensing / evaporating (or boiling) / freezing) → meltingPrompt: Heating makes solids melt and liquids evaporate.
  3. Changes of state: which statement is true? (Water only evaporates when it boils. / Melting makes a substance lose mass. / The water on the outside of a cold can leaks through the metal. / Heating can make a solid melt.) → Heating can make a solid melt.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: water freezing into ice cubes? (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 CAN be undone. Which one is different? (toasting bread / an ice lolly (popsicle) melting / water freezing into ice cubes / chocolate melting in a warm hand) → toasting breadPrompt: 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. Three of these changes CAN be undone. Which one is different? (an ice lolly (popsicle) melting / frying an egg / water freezing into ice cubes / candle wax melting) → frying an eggPrompt: Think about melting and freezing versus cooking and burning.
  2. Ice cream is left in the sun and melts. Then it is put back in the freezer. Is it the same as before? (It burns. / It stays a liquid in the freezer. / It turns into milk powder. / It freezes solid again, though it may be icier and harder than before.) → It freezes solid again, though it may be icier and harder than before.Prompt: Is melting a change that can be reversed?

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

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

    • A. toasting bread
    • B. frying an egg
    • C. baking a cake
    • D. candle wax melting

  2. Question 2

    Can this change be undone: butter softening in a warm kitchen?

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

  3. Question 3

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

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

  4. Question 4

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

    • A. butter softening in a warm kitchen
    • B. frying an egg
    • C. water freezing into ice cubes
    • D. candle wax melting

  5. Question 5

    Can this change be undone: toasting bread?

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

  6. Question 6

    Clay is shaped into a pot and baked in a very hot kiln. Can it go back to soft clay if you add water?

    • A. No, firing changes it for good.
    • B. Yes, if you put it in the freezer.
    • C. Yes, straight away.
    • D. Yes, if you shake it.

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

  1. 1. D. candle wax melting

  2. 2. A. can change back

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

  4. 4. B. frying an egg

  5. 5. B. cannot change back

  6. 6. A. No, firing changes it for good.