Compare hot and humid to hot and windy or hot and cloudy environments. What percentage of an orange is water?
Blowing bubbles may sound like too much fun for a science project, but when conditions, like temperature, are altered, the experimental part kicks in.
If not, is there a relationship between them? Test PH using cabbage. This experiment requires nothing more than newspaper and masking tape!
Oxidation experiments can be as simple as dropping objects into water to see if they rust or made more complex by altering the conditions to see if rusting can be delayed or prevented. You can also experiment with the resulting velocities after a collision between a moving object and unmoving one, or between two objects moving in opposite directions.
This experiment explores how charcoal filters impurities from drinking water. Do a thermal conductivity study to discover which substance works best for a pot handle and which works best for a teapot.