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Science lesson plan · 3rd grade (Year 4 in England) · 30 minutes

Planning a fair test

Working scientifically

CCSS NGSS.SEP 3CCSS NGSS.3-PS2-1England: KS2 Y3–Y4 Working scientifically

Objective and success criteria

Students will: Planning a fair test.

  • 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: Choosing a measuring tool

Leads to: Independent, dependent and control variables

Materials: Simple equipment for a fair test, Results table template, Mini whiteboards, A diagram or short video clip of the idea, Printed student sheet (below).

Warm-up · 4 min

  • Quick retrieval from earlier learning (Choosing a measuring tool). Students answer on mini whiteboards.
  • Show answers together and note who needs support in the main task.
  1. Which tool would you use to measure the mass of a bag of flour? (weighing scales / a stopwatch or timer / a ruler or tape measure / a measuring jug or cylinder) → weighing scalesPrompt: Is it a length, a temperature, a mass, a time or an amount of liquid?
  2. What could you measure with a ruler or tape measure? (how cold the water in a pond is / how long an ice cube takes to melt / how tall a sunflower has grown / how long a candle burns) → how tall a sunflower has grownPrompt: What does this tool measure: length, temperature, mass, time or volume?
  3. Which is the best tool to find out how long it takes a snail to cross a table? (a ruler / a rain gauge / a thermometer / a stopwatch) → a stopwatchPrompt: "How long it takes" is about time.

Hook · 3 min

  • Show a simple experiment with one thing changed and ask what makes it a fair test.
  • Share the objective: Planning a fair test. 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: Leo tests which paper towel soaks up the most water. What should he change?
  • Step 1: He is testing types of paper towel, so that is the only thing he changes.
  • Step 2: So the answer is: the type of paper towel
  • Answer: the type of paper towel
  • 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. Leo tests which paper towel soaks up the most water. What should he change? (the amount of water / the time he waits / the size of the towel / the type of paper towel) → the type of paper towelPrompt: In a fair test you change only one thing: the thing you are testing.
  2. Ben tests whether salt water or tap water freezes faster. Which must he keep the same? (whether the water has salt / the type of water / the time each one takes to freeze / the volume of water in each cup) → the volume of water in each cupPrompt: He is changing the type of water and measuring the time.

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. Fair tests: which statement is true? (A prediction says what you think will happen. / If a result surprises you, you should hide it. / You should change as many things as possible. / One try is always enough.) → A prediction says what you think will happen.Prompt: Think about what makes a test fair.
  2. Leo tests which paper towel soaks up the most water. What should he change? (the size of the towel / the time he waits / the type of paper towel / the amount of water) → the type of paper towelPrompt: In a fair test you change only one thing: the thing you are testing.

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: Choosing a measuring tool.
  • Use concrete materials: simple equipment for a fair test.
  • 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: Independent, dependent and control variables.
  • 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-3.

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

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Planning a fair test

Name

Date

Score/ 6

  1. Question 1

    Why is it a good idea to repeat a test several times?

    • A. To check the results are reliable
    • B. To make the test unfair
    • C. To change the answer
    • D. Because the first try never counts

  2. Question 2

    Omar tests how the length of a guitar string changes its note. He uses strings of different lengths. What else should stay the same?

    • A. the note he hears
    • B. the length of the strings
    • C. nothing else matters
    • D. how tight and thick the strings are

  3. Question 3

    Fair tests: which statement is true?

    • A. If a result surprises you, you should hide it.
    • B. One try is always enough.
    • C. In a fair test you change only one thing.
    • D. You should change as many things as possible.

  4. Question 4

    Isla tests which ball bounces highest. She drops one ball from 1 m and another from 2 m. What is wrong?

    • A. She should use only one ball
    • B. Nothing, it is fair
    • C. The drop height should be the same
    • D. She should not measure the bounce

  5. Question 5

    Which question can be answered with a fair test?

    • A. What is your favourite plant?
    • B. Who is the best scientist?
    • C. Is a rainbow beautiful?
    • D. Does a heavier parachute fall faster?

  6. Question 6

    Leo tests which paper towel soaks up the most water. What should he change?

    • A. the time he waits
    • B. the type of paper towel
    • C. the amount of water
    • D. the size of the towel

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Answer key: Planning a fair test

  1. 1. A. To check the results are reliable

  2. 2. D. how tight and thick the strings are

  3. 3. C. In a fair test you change only one thing.

  4. 4. C. The drop height should be the same

  5. 5. D. Does a heavier parachute fall faster?

  6. 6. B. the type of paper towel

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