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Science lesson plan · 6th grade (Year 7 in England) · 30 minutes

Spot the evidence that a chemical reaction happened

Chemical reactions, acids and bases

CCSS NGSS.MS-PS1-2England: KS3 Chemistry: Chemical reactions

Objective and success criteria

Students will: Spot the evidence that a chemical reaction happened.

  • 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: Physical and chemical changes

Leads to: Conservation of mass in reactions

Materials: Teacher demo or video, Indicator color chart, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).

Warm-up · 4 min

  • Quick retrieval from earlier learning (Physical and chemical changes). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. Is this a physical or a chemical change: iron rusting? (physical change / chemical change) → chemical changePrompt: Is a new substance made?
  2. A nail left outside turns orange-brown and flaky. What has happened? (Iron reacted with oxygen and water to make rust / The nail melted / The nail dissolved / Paint fell on it) → Iron reacted with oxygen and water to make rustPrompt: Rusting needs both air and water.
  3. Physical and chemical changes: which statement is NOT true? (Rusting needs both oxygen and water. / Dissolving is a physical change. / Atoms are destroyed in chemical reactions. / Burning is a chemical change.) → Atoms are destroyed in chemical reactions.Prompt: Does each change make a new substance?

Hook · 3 min

  • Drop an antacid tablet in water (or show a clip) and ask whether a new substance is being made.
  • Share the objective: Spot the evidence that a chemical reaction happened. 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: What evidence of a chemical reaction is shown here: a shiny iron nail slowly turns orange-brown in damp air?
  • Step 1: A new colour can show a new substance has formed.
  • Step 2: So the answer is: a colour change
  • Answer: a colour change
  • 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. What evidence of a chemical reaction is shown here: a cut apple turns brown? (a gas is given off / a colour change / a solid (precipitate) forms / an energy change (heat or light)) → a colour changePrompt: Did you see bubbles, a new colour, a new solid or an energy change?
  2. Bread is toasted and goes brown and crisp. What kind of change is this? (no change at all / physical, because it is still bread / physical, because it is only heated / chemical, because new substances form that cannot be turned back into bread) → chemical, because new substances form that cannot be turned back into breadPrompt: Can you "untoast" the bread?

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. Chemical reactions: which statement is NOT true? (Atoms are destroyed in chemical reactions. / In a chemical reaction, new substances are made. / Dissolving salt in water is a physical change. / Rusting is a chemical change.) → Atoms are destroyed in chemical reactions.Prompt: Is a new substance always made when bubbles appear?
  2. What evidence of a chemical reaction is shown here: two clear solutions are mixed and a yellow solid appears? (a gas is given off / a colour change / a solid (precipitate) forms / an energy change (heat or light)) → a solid (precipitate) formsPrompt: Did you see bubbles, a new colour, a new solid or an energy change?

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: Physical and chemical changes.
  • Use concrete materials: teacher demo or video.
  • 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: Conservation of mass in reactions.
  • 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-6.

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

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Spot the evidence that a chemical reaction happened

Name

Date

Score/ 6

  1. Question 1

    Ice melts into water. A student says this is a chemical reaction because it changes. Why is this wrong?

    • A. All changes are chemical reactions
    • B. Ice and water are different elements
    • C. Melting releases a new gas
    • D. No new substance forms: it is still water, so it is a physical change

  2. Question 2

    Chemical reactions: which statement is NOT true?

    • A. Atoms are destroyed in chemical reactions.
    • B. In a chemical reaction, new substances are made.
    • C. Rusting is a chemical change.
    • D. Many chemical reactions are hard to reverse.

  3. Question 3

    What evidence of a chemical reaction is shown here: a shiny iron nail slowly turns orange-brown in damp air?

    • A. a gas is given off
    • B. a colour change
    • C. a solid (precipitate) forms
    • D. an energy change (heat or light)

  4. Question 4

    Bread is toasted and goes brown and crisp. What kind of change is this?

    • A. chemical, because new substances form that cannot be turned back into bread
    • B. physical, because it is only heated
    • C. physical, because it is still bread
    • D. no change at all

  5. Question 5

    What evidence of a chemical reaction is shown here: an instant cold pack gets cold when squeezed?

    • A. a gas is given off
    • B. a colour change
    • C. a solid (precipitate) forms
    • D. an energy change (heat or light)

  6. Question 6

    What evidence of a chemical reaction is shown here: bubbles form when an antacid tablet is dropped in water?

    • A. a gas is given off
    • B. a colour change
    • C. a solid (precipitate) forms
    • D. an energy change (heat or light)

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Answer key: Spot the evidence that a chemical reaction happened

  1. 1. D. No new substance forms: it is still water, so it is a physical change

  2. 2. A. Atoms are destroyed in chemical reactions.

  3. 3. B. a colour change

  4. 4. A. chemical, because new substances form that cannot be turned back into bread

  5. 5. D. an energy change (heat or light)

  6. 6. A. a gas is given off