Chemistry Experiment ideas

I have just completed year 11 and in a week will be starting sixth form. For my chosen subjects there is homework which are called transition projects that I need to do. For chemistry it says I need to conduct an experiment but I'm not really sure what to do the experiment on.
This is what the task says. "Carry out your own investigation into Chemistry of a question of your own choosing. This must be a simple, safe experiment using only normal household substances that do not carry hazard symbols on their labels. This is an opportunity to be creative and maybe find an answer to a question that’s been bothering/intriguing you. It should be predominantly Chemistry but some Bio/Phys crossover is fine. You need to be ready to present/discuss your investigation and your findings.
E.g. I could decide to investigate how much salt/sugar I could add to an absolutely full (deliberately overflowed on a flat surface and then allowed to stand until it stopped overflowing) glass of water without it overflowing. I could then investigate the effect of detergent on surface tension by repeating my original expt. with different amounts of detergent added."
Any suggestions would go appreciated