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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Every experiment you will meet this year follows the same five steps.
🧭 The five steps
Observe something and ask a question about it.
Make a hypothesis — a testable guess, not a wish.
Experiment, changing only one thing at a time.
Record the results honestly, even the ones you did not expect.
Conclude — and if the result disagrees with your guess, the guess was wrong, not the result.
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.
A test is fair only when you change one thing and keep everything else the same.
⚖️ The three kinds of variable
| Name | Meaning | In a plant experiment |
|---|---|---|
| Independent | the one thing you change | hours of sunlight |
| Dependent | what you measure | height of the plant |
| Controlled | everything you keep the same | water, soil, pot size, seed type |
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.
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.
A measurement without a unit means nothing. "The rod is 15" tells you nothing at all.
📏 SI units you must know
| Quantity | Unit | Symbol |
|---|---|---|
| Length | metre | m |
| Mass | kilogram | kg |
| Time | second | s |
| Temperature | kelvin (celsius in daily use) | K (°C) |
| Volume | cubic metre; litre in daily use | m³ (L) |
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.
12 questions on scientific method and measurement. 🍀
