Question

What variables would I use in this experiment?

I am answering the question: How does adding salt affect the freezing point of water?

Hypothesis: If salt is added to water, then the water will go through a physical change and the waters freezing point will be lowered.

Answer 1

Think about how you would test this. The simplest way would be to get two cups. Into those two cups put an equal amount of water. The amount of water and the shape of each cup need to be the same - because if they were different (i.e., variable) they would affect how quickly the water inside them froze.

Into one cup I would but a lot of salt. Then I would put the two cups (one salted, one fresh water) side by side in the same freezer (or outside on the same freezing windowsill, if like me you live somewhere that hasn't seen the upside of freezing in three months - meh) and see what froze first.

Think about the factors in this set up - cup size and shape, water amount, temperature, salt level in the water - and think about which are the same for both cup and which are different.