okay, I've finalised this!
I'm going to do:

What type of plastic wrap prevents evaporation best?

Okay well, not that I got that out of the way I can set up everything I need.

Aim: To investigate which type of plastic wrap prevents evaporation best.

Hypothesis: The thinner the sheet of plastic, the more the liquid will evaporate.

Equipment: 5 different containers, 5 different brands/sheets of plastic.

Method:

1. Pour 250mL of water into container
2. Cut out a 30cm x 30cm sheet of plastic.
3. Place plastic over the container and securely wrap it around all edges
4. Wait 4 days
5. Take off sheet of plastic and measure the amount of water left in container
6. Record observations
7. Repeat steps 1-6 with different plastics