Controlling variables (age 11+) · seed 1 · A4, ink-friendly. The answer key prints on its own page for grown-ups.

Writing a hypothesis and planning a fair test

Science · Scientific Inquiry · ages 11-12
Name ______________________   Date ____________

  1. In an investigation about whether temperature affects how fast sugar dissolves, what is the independent variable, the one thing you deliberately change?

    • The time taken for the sugar to dissolve
    • The temperature of the water
    • The amount of sugar used

  2. Which sentence is written as a proper scientific hypothesis?

    • I predict that increasing water temperature will affect how quickly sugar dissolves, because heat makes the particles move faster.
    • Sugar dissolves faster in hot water.
    • Hot water is better for dissolving sugar.

  3. Control variables are the things you keep the same so the test is fair.

    Circle one:   True   False

  4. Which of these should stay exactly the same every time, as a control variable?

    • The amount of sugar added each time
    • The temperature of the water
    • The time taken for the sugar to dissolve

  5. What is the dependent variable in the sugar-dissolving investigation, the thing you measure?

    • The temperature of the water
    • The amount of water used
    • The time taken for the sugar to dissolve

  6. Priya repeats the hot-water test and records 30, 32, and 31 seconds. How many repeat readings has she taken in total?

    Answer: ______________

  7. A student is testing how water temperature affects dissolving, using water heated in a kettle. Which is the most sensible safety step?

    • Checking the water temperature with a bare finger
    • Leaving the hot water unattended to save time
    • Wearing oven gloves or asking an adult to pour the hot water

  8. Bilal writes: 'I predict that more light will affect plant height.' What part of a proper hypothesis is missing?

    • The independent variable
    • A reason using 'because' to explain the science
    • The dependent variable
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Answer key

For grown-ups. Fold this page away before handing over the rest.

Writing a hypothesis and planning a fair test W1-mt_Ae56umVlTT-s1

  1. The temperature of the water · The independent variable is the thing you choose to change on purpose, in this case the water temperature.
  2. I predict that increasing water temperature will affect how quickly sugar dissolves, because heat makes the particles move faster. · A hypothesis names the variable you change, the variable you measure, and gives a reason using 'because'.
  3. True · If you don't hold the control variables constant, you can't tell what really caused any change in your results.
  4. The amount of sugar added each time · The water temperature is what you're testing and the time is what you measure, so the sugar amount must be the thing kept constant.
  5. The time taken for the sugar to dissolve · The dependent variable is the result you measure after changing the independent variable, here the dissolving time.
  6. 3 · She measured the same test three separate times, a good minimum for trusting the result.
  7. Wearing oven gloves or asking an adult to pour the hot water · A good risk assessment names the hazard, hot water, and pairs it with a control measure that reduces the risk of a burn.
  8. A reason using 'because' to explain the science · Bilal already named the variables, but a hypothesis also needs a reason that explains why he expects that result.
Worksheet · LightMySky