Science · Stage 6

Controlled Experiments

A fair test changes just one thing (the independent variable), measures the result (the dependent variable), and keeps everything else (the controlled variables) exactly the same — so you can trust what caused the result.

✦ Science📘 Stage 6 · S6⏱ ~12 min🧒 Ages 10–12★ Free to start

I can work out whether an experiment is a fair, controlled test, or not.

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Kavi Catches a Sneaky Second Change

Kavi lines up two toy cars at the top of a ramp 🚗. "I want to know if a higher ramp makes a car roll farther. So I change the ramp height — and only that! Same car, same floor, same little push. If I'd also swapped in a heavier car, I'd never know whether it was the ramp or the car that made the difference. A real scientist changes one thing, measures the result, and keeps everything else the same. Come help me spot the fair tests — and catch the sneaky ones that secretly change two things at once!"

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What your child will learn

1Every experiment has these three jobsIn a controlled experiment, each thing has a job. Tap each one to see what it does.

2One change, or two?Tap each test. A fair test changes just one variable; an unfair test changes more than one, so you cannot tell what caused the result.

3Fair, or not fair?Read each test and tap your answer. Tap Next test for more.

4Sort the testsWhich of these are fair, controlled tests, and which ones secretly change more than one thing?

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A peek inside

A class asks: does a taller ramp make a toy car roll farther? They set the ramp higher each go, use the same car and the same floor, and measure the distance. Which is the independent variable?

The independent variable is the one thing they deliberately change. The car and the floor stay the same, and the distance is what they measure. The only thing they change is the ramp height — so the ramp height is the independent variable.

Try this at home: In a fair test, how many variables should you change at a time?

Ready to play and learn?

Start the free interactive lesson, or print the handout for screen-free play.

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Part of Science · Stage 6 · S6 on KAVI Academy — a secular, whole-child learning platform for ages 5–12.