Science · Stage 6

Challenge: Advanced Olympiad Reasoning

Two things changed, not one — so before you believe any claim, hunt down every rival explanation and rule each one out.

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

I can work out questions like: “Before claiming the dark soil caused it, what else should you check?”

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Kavi and the Case of the Dark Soil

Kavi pulls on a tiny detective hat 🔍. "A young scientist told me her plants grew taller in dark soil — so the soil must be magic! But wait…" Kavi taps the pots. "Those pots also sat in the sunniest spot. Before I believe any claim, I hunt down every rival explanation and check it — sunlight, water, warmth, even the seeds themselves. A real scientist never stops at the first idea. Come be my detective — what else should we check?"

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What your child will learn

1Four checks before you believe a claimA claim is only defended once you have ruled out every rival explanation. Tap each check to see how a scientist thinks.

2Has every rival been ruled out?Read each case. Is it safe to accept the claim, or is there a rival left to check? Tap your answer, then tap Next test.

3Which differences could be the real cause?Dark-soil plants grew taller. Sort each difference: is it a rival cause you must check, or something that cannot matter?

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A peek inside

Dark-soil plants grew taller — and those pots also sat on the sunniest shelf. Someone says 'the dark soil caused it.' What should you check first?

Two things were different, not one: the soil AND the sunlight. So the taller growth could be caused by the extra sun, not the soil. Before I accept the claim, I must rule out that rival — run a fair test where the ONLY difference is the soil (same light, same water, same seeds), or check whether the sunniest plants would have grown taller anyway.

Try this at home: Two pots grew differently, but they had different soil AND different light. Can you blame the soil? Why?

Ready to play and learn?

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

Start the free lesson →⬇ Download PDF

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