How to Write a PSLE Science Experiment Aim

Picture this. Two students are in the hall, each with a ball and a measuring tape.

Aisha drops the same tennis ball from 50 cm, then 100 cm, then 150 cm. Each time she measures how high it bounces.

Ravi drops three different balls — a tennis ball, a basketball, a ping pong ball — all from 100 cm. Each time he measures how high it bounces.

To anyone watching from the doorway, they're doing much the same thing. Dropping balls, measuring bounces, writing numbers in a table. But each of them knows exactly what they're testing, and it isn't the same thing.

Aisha is finding out how the height a ball is dropped from affects how high it bounces.

Ravi is finding out how the type of ball affects how high it bounces.

That sentence is the aim. It's what makes the two experiments different. It's also the only place that difference shows up.

Using what you learnt in Episode 2

Look at those two aims again. Each one names exactly two things, and you already know what they're called.

Aisha — changed variable: the height it's dropped from. Measured variable: how high it bounces.

Ravi — changed variable: the type of ball. Measured variable: how high it bounces.

Same measured variable. A different changed variable. That one difference is the whole difference between the two experiments.

So the aim isn't a new thing to learn. It's the two variables you sorted in Episode 2, joined by one word:

<changed variable> affects <measured variable>

Get the sorting right and the sentence has almost written itself.

Three things an aim is not. It isn't the method. It isn't a guess at the result. It isn't what was found.

What a strong answer does

• Says one thing affects the other. "To find out about fertiliser and plant height" gives two nouns and no link between them. The word "affects" is what turns them into a claim.
• Matches the set-up exactly. Did the set-up change the amount of fertiliser in grams? Then write "the amount of fertiliser", not just "fertiliser". The exact phrase is the one that counts. Same habit as in Say This, Not That.
• Says what was being found out, not what was done. "To grow four plants with different amounts of fertiliser and measure their height" is the method. An aim opens with "to find out", "to investigate" or "to determine".
• Puts the cause first. "To find out how the height of the plant affects the amount of fertiliser" has it backwards — a plant's height can't change how much fertiliser you pour. Both nouns are right and the sentence still doesn't work, so the order is worth a quick check.

Run one check before you move on. Both variables, cause first, linked by "affects".

For more tips on improving your answers—from avoiding common mistakes to using precise science language—explore the complete PSLE Science OEQ Guide.