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Science lesson plan · 8th grade (Year 9 in England) · 45 minutes

Exothermic and endothermic reactions

Chemical reactions, acids and bases

CCSS NGSS.MS-PS1-6CCSS NGSS.HS-PS1-4England: KS3 Chemistry: EnergeticsEngland: KS4 Combined Science: Energy changes in chemistry

Objective and success criteria

Students will: Exothermic and endothermic reactions.

  • 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: Reactants, products and word equations

Leads to: Rates of reaction; Reaction profiles: energy change and activation energy

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 · 5 min

  • Quick retrieval from earlier learning (Reactants, products and word equations). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. Complete the word equation: iron + oxygen → ___ (iron oxide / carbon dioxide / iron carbonate / iron chloride) → iron oxidePrompt: A metal reacting with oxygen makes a metal oxide.
  2. Methane burns completely in air: methane + oxygen → carbon dioxide + ___ (hydrogen / nitrogen / water / carbon monoxide) → waterPrompt: Methane contains carbon and hydrogen. What does hydrogen become when it burns?
  3. Word equations: which statement is NOT true? (Combustion is a reaction with oxygen. / Incomplete combustion can produce carbon monoxide, a poisonous gas. / Products are the substances you start with. / Reactants are written on the left of the arrow.) → Products are the substances you start with.Prompt: Which side of the arrow is which?

Hook · 5 min

  • Drop an antacid tablet in water (or show a clip) and ask whether a new substance is being made.
  • Share the objective: Exothermic and endothermic reactions. Read the success criteria together.

I do: model it · 10 min

  • Work through the example out loud, saying why you do each step, not just what you do.
  • Example: Is this exothermic or endothermic: thermal decomposition of calcium carbonate?
  • Step 1: Endothermic reactions take in energy from the surroundings, so the temperature falls.
  • Step 2: So the answer is: endothermic
  • Answer: endothermic
  • Pause after each step and ask a student to say what comes next.

We do: guided practice · 10 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. Is this exothermic or endothermic: neutralising an acid with an alkali? (exothermic / endothermic) → exothermicPrompt: Does it give out heat or take heat in?
  2. The temperature of a reaction mixture changes from 19 °C to 11 °C. What is the temperature change? (Use a minus sign for a fall.) → -8 °CPrompt: Change = final temperature − starting temperature.

You do: independent practice · 10 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 8 questions are on the student sheet below, with answers in the key.

Exit ticket · 5 min

  • Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
  1. Breaking chemical bonds… (has no energy change / takes in energy (endothermic) / gives out energy (exothermic) / creates new atoms) → takes in energy (endothermic)Prompt: You have to put energy in to pull atoms apart.
  2. Is this exothermic or endothermic: burning methane? (exothermic / endothermic) → exothermicPrompt: Does it give out heat or take heat in?

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: Reactants, products and word equations.
  • 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: Rates of reaction; Reaction profiles: energy change and activation energy.
  • 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-8.

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

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Exothermic and endothermic reactions

Name

Date

Score/ 8

  1. Question 1

    In an exothermic reaction, the energy of the products is…

    • A. exactly the same as the reactants
    • B. higher than the energy of the reactants
    • C. lower than the energy of the reactants
    • D. zero

  2. Question 2

    Is this exothermic or endothermic: neutralising an acid with an alkali?

    • A. exothermic
    • B. endothermic

  3. Question 3

    The temperature of a reaction mixture changes from 20 °C to 42 °C. What is the temperature change? (Use a minus sign for a fall.)

    Answer°C

  4. Question 4

    Is this exothermic or endothermic: burning methane?

    • A. exothermic
    • B. endothermic

  5. Question 5

    The temperature of a reaction mixture changes from 21 °C to 6 °C. What is the temperature change? (Use a minus sign for a fall.)

    Answer°C

  6. Question 6

    Breaking chemical bonds…

    • A. creates new atoms
    • B. has no energy change
    • C. gives out energy (exothermic)
    • D. takes in energy (endothermic)

  7. Question 7

    Is this exothermic or endothermic: respiration?

    • A. exothermic
    • B. endothermic

  8. Question 8

    The temperature of a reaction mixture changes from 22 °C to 26 °C. What is the temperature change? (Use a minus sign for a fall.)

    Answer°C

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Answer key: Exothermic and endothermic reactions

  1. 1. C. lower than the energy of the reactants

  2. 2. A. exothermic

  3. 3. 22 °C

  4. 4. A. exothermic

  5. 5. -15 °C

  6. 6. D. takes in energy (endothermic)

  7. 7. A. exothermic

  8. 8. 4 °C