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Chapter 1 · The Investigative World of Science

NCERT Class 8 · Curiosity

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CHAPTER 1 OF 13

The Investigative World of Science 🔬

Science is not a pile of facts to remember. It is a way of finding out — ask a question, guess an answer, test it fairly, and let the result decide.

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Part 1 · The Method

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Part 2 · Fair Testing

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Part 3 · Measuring

1

How an investigation works 🧭

Every experiment you will meet this year follows the same five steps.

🧭 The five steps

1

Observe something and ask a question about it.

2

Make a hypothesis — a testable guess, not a wish.

3

Experiment, changing only one thing at a time.

4

Record the results honestly, even the ones you did not expect.

5

Conclude — and if the result disagrees with your guess, the guess was wrong, not the result.

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A hypothesis must be testable. "Plants grow taller with more sunlight" can be tested. "Plants like sunlight" cannot — you cannot measure liking. Exam questions often ask you to spot which statement is a proper hypothesis.

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Game 1 — Order the Steps

2

A fair test ⚖️

A test is fair only when you change one thing and keep everything else the same.

⚖️ The three kinds of variable

NameMeaningIn a plant experiment
Independentthe one thing you changehours of sunlight
Dependentwhat you measureheight of the plant
Controlledeverything you keep the samewater, soil, pot size, seed type
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Why a control group matters. If every plant gets fertiliser you cannot tell whether the fertiliser did anything. Keeping one group without it gives you something to compare against.

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Repeat before you believe. One reading can be luck or a mistake. Scientists repeat a measurement several times and take the average, which makes a stray reading obvious.

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Game 2 — Which Variable?

3

Measuring and recording 📏

A measurement without a unit means nothing. "The rod is 15" tells you nothing at all.

📏 SI units you must know

QuantityUnitSymbol
Lengthmetrem
Masskilogramkg
Timeseconds
Temperaturekelvin (celsius in daily use)K (°C)
Volumecubic metre; litre in daily usem³ (L)
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Mass and weight are not the same. Mass is how much matter a thing contains, measured in kilograms, and it never changes. Weight is the pull of gravity on it, measured in newtons, and it does change — you weigh less on the moon but your mass is identical.

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Game 3 — Quantity and Unit

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Topic Mock Test

12 questions on scientific method and measurement. 🍀

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Chapter 2 · The Invisible Living World 🦠