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Science lesson plan · 9th grade (Year 10 in England) · 30 minutes

Rates of reaction

Chemical reactions, acids and bases

CCSS NGSS.HS-PS1-5England: KS4 Combined Science: The rate and extent of chemical change

Objective and success criteria

Students will: Rates of reaction.

  • 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: Exothermic and endothermic reactions

Leads to: Calculate mean rates of reaction from data; Predict how an equilibrium shifts (Le Chatelier)

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 (Exothermic and endothermic reactions). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. Is this exothermic or endothermic: respiration? (exothermic / endothermic) → exothermicPrompt: Does it give out heat or take heat in?
  2. The temperature of a reaction mixture changes from 19 °C to 5 °C. What is the temperature change? (Use a minus sign for a fall.) → -14 °CPrompt: Change = final temperature − starting temperature.
  3. Breaking chemical bonds… (has no energy change / creates new atoms / takes in energy (endothermic) / gives out energy (exothermic)) → takes in energy (endothermic)Prompt: You have to put energy in to pull atoms apart.

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: Rates of reaction. 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: A reaction produces 150 cm³ of gas in 50 seconds. What is the mean rate of reaction, in cm³/s?
  • Step 1: 150 ÷ 50 = 3
  • Step 2: So the answer is: 3 cm³/s
  • Answer: 3 cm³/s
  • 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. A reaction produces 25 cm³ of gas in 50 seconds. What is the mean rate of reaction, in cm³/s? → 0.5 cm³/sPrompt: mean rate = amount of product ÷ time
  2. What does a catalyst do? (is used up in the reaction / slows down a reaction / changes the products / speeds up a reaction without being used up) → speeds up a reaction without being used upPrompt: Enzymes are biological examples.

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. Rates of reaction: which statement is NOT true? (A catalyst is not used up in a reaction. / Food lasts longer in a fridge because reactions are slower at low temperature. / Every collision between particles causes a reaction. / Increasing surface area increases the rate.) → Every collision between particles causes a reaction.Prompt: What does a catalyst change, and what does it not change?
  2. Why does powdered marble react faster with acid than marble chips? (Powder has more mass / Chips are hotter / Powder has a larger surface area, so there are more collisions / Powder is a different substance) → Powder has a larger surface area, so there are more collisionsPrompt: Cutting something up exposes more of it.

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: Exothermic and endothermic reactions.
  • 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: Calculate mean rates of reaction from data; Predict how an equilibrium shifts (Le Chatelier).
  • 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-9.

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

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Rates of reaction

Name

Date

Score/ 6

  1. Question 1

    A reaction produces 15 cm³ of gas in 30 seconds. What is the mean rate of reaction, in cm³/s?

    Answercm³/s

  2. Question 2

    Rates of reaction: which statement is NOT true?

    • A. Lower temperatures make reactions faster.
    • B. Increasing surface area increases the rate.
    • C. A catalyst is not used up in a reaction.
    • D. Food lasts longer in a fridge because reactions are slower at low temperature.

  3. Question 3

    Why does increasing the temperature speed up a reaction?

    • A. Particles get bigger
    • B. It adds more particles
    • C. Particles move faster, collide more often and more collisions have enough energy
    • D. It lowers the activation energy

  4. Question 4

    A reaction produces 90 cm³ of gas in 60 seconds. What is the mean rate of reaction, in cm³/s?

    Answercm³/s

  5. Question 5

    Why does powdered marble react faster with acid than marble chips?

    • A. Powder has more mass
    • B. Powder has a larger surface area, so there are more collisions
    • C. Chips are hotter
    • D. Powder is a different substance

  6. Question 6

    A reaction produces 150 cm³ of gas in 50 seconds. What is the mean rate of reaction, in cm³/s?

    Answercm³/s

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Answer key: Rates of reaction

  1. 1. 0.5 cm³/s

  2. 2. A. Lower temperatures make reactions faster.

  3. 3. C. Particles move faster, collide more often and more collisions have enough energy

  4. 4. 1.5 cm³/s

  5. 5. B. Powder has a larger surface area, so there are more collisions

  6. 6. 3 cm³/s