Help! I need a science project idea.?

As a graded project, I, along with two others have to choose a scientific question and create a hypothesis based on it, then carry out an experiment to compare to our hypothesis. For example one group chose "How does hunger affect taste?" Where they will make multiple subjects consume something when they're hungry and when they're not, in order to compare their perceptions of the food's taste under the different conditions. We have about a week to do it. The topics we can choose from are: Water, Forces, food, plastics, the solar system, chemical reactions and plant growth. Any plausible ideas would be much appreciated