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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: ice melting? (physical change / chemical change) → physical changePrompt: Is a new substance made?
  2. Which is a chemical change you might see in a kitchen? (toasting bread / melting butter / freezing juice / chopping carrots) → toasting breadPrompt: Which one makes a new substance with a new colour and smell?
  3. Physical and chemical changes: which statement is NOT true? (All bubbles mean a chemical reaction. / Burning is a chemical change. / In a chemical reaction, atoms are rearranged to make new substances. / Dissolving is a physical change.) → All bubbles mean a chemical reaction.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: 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?
  2. Ice melts into water. A student says this is a chemical reaction because it changes. Why is this wrong? (All changes are chemical reactions / No new substance forms: it is still water, so it is a physical change / Melting releases a new gas / Ice and water are different elements) → No new substance forms: it is still water, so it is a physical changePrompt: Is the substance after the change different from before?

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? (In a chemical reaction, new substances are made. / Rusting is a chemical change. / Dissolving salt in water is a physical change. / Boiling water is a chemical reaction because bubbles form.) → Boiling water is a chemical reaction because bubbles form.Prompt: Is a new substance always made when bubbles appear?
  2. What evidence of a chemical reaction is shown here: a glow stick gives out light when bent? (a gas is given off / a colour change / a solid (precipitate) forms / an energy change (heat or light)) → an energy change (heat or light)Prompt: 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

    Which observation is the strongest evidence that burning a candle is a chemical change?

    • A. The wax melts
    • B. Carbon dioxide and water vapour are made, and energy is released as heat and light
    • C. The candle gets shorter
    • D. The wick is white

  2. Question 2

    Chemical reactions: which statement is NOT true?

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

  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

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

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

  5. Question 5

    What evidence of a chemical reaction is shown here: a hand warmer gets hot when opened?

    • 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: a cut apple turns brown?

    • 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. B. Carbon dioxide and water vapour are made, and energy is released as heat and light

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

  3. 3. B. a colour change

  4. 4. B. No new substance forms: it is still water, so it is a physical change

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

  6. 6. B. a colour change