Testing and comparing carefully
Chemistry · Key Stage 1 · The School
Same way, every time
You want to compare two cloths. Which one soaks up more water? Use the SAME amount of water on each. Use the SAME size cloth. Give each one the SAME time. If you pour more water on one, you have learned nothing about the cloths. You have only learned that more water is wetter. And you knew that already.
Measuring without a ruler
You do not always need numbers. You can line things up side by side. You can use the same cup each time. You can count how many blocks tall something is. You can see which one happens first. Comparing directly is real measuring. It comes before measuring with units.
Saying how you know
Here is the useful sentence. This one was best BECAUSE. The blue cloth soaked up most, because the water disappeared fastest and the cloth felt heaviest. Giving the reason turns an opinion into a finding. And the reason is what someone else needs, in order to believe you.
Which kitchen towel soaks up most? Ali pours water on towel A from a jug. He dips towel B into a bowl. That is unfair. Two things changed at once. So the result means nothing. Here is the fair version. Same amount of water, say 20 ml. Same way of adding it. Same size piece of each towel. Same time to soak. Then weigh each one. Only one thing changed, the towel. Everything else was held still.