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Planning a fair test
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Scientists answer questions by testing ideas. A good test is fair, safe and can be repeated.
Questions and predictions
An investigation starts with a question, often from something you have noticed.
A prediction says what you think will happen and why, using science you already know.
Example: "The warmer the water, the faster sugar dissolves, because the particles move faster."
A prediction says what you think will happen and why, using science you already know.
Example: "The warmer the water, the faster sugar dissolves, because the particles move faster."
Three kinds of variable
Independent variable: the one thing you choose to change.
Dependent variable: the thing you measure.
Control variables: everything you keep the same, so the test is fair.
Dependent variable: the thing you measure.
Control variables: everything you keep the same, so the test is fair.
Safe and trustworthy
A risk assessment lists the hazards (what could cause harm) and how to reduce the risk, for example wearing eye protection when heating.
Repeat readings to check they are repeatable. If other people get the same results with different kit, the results are reproducible.
Scientists share results so other scientists can check them (peer review). Ideas change when new evidence appears.
Repeat readings to check they are repeatable. If other people get the same results with different kit, the results are reproducible.
Scientists share results so other scientists can check them (peer review). Ideas change when new evidence appears.
Amira tests how the height a ball is dropped from affects how high it bounces. Name the independent and dependent variables, and one control variable.
- She chooses the drop height, so that is the independent variable.
- She measures the bounce height, so that is the dependent variable.
- She must keep the same ball and the same floor surface.
Answer: Independent: drop height. Dependent: bounce height. Control: the same ball (or the same floor).
Change one variable (independent), measure one variable (dependent), keep the rest the same (control). Assess risks, repeat readings and share results so others can check them.
The interactive lesson includes the diagrams for this topic.
Check you have got it
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