Record the length of the spark. Try the same experiment on a warm day. Be sure to have the same shoes or socks on. Record the spark length. Compare with the results of a cold day.
Static electricity is a real danger for computers.
Test a new fishing lure. Be careful to keep the variables of location, depth, rate and method of retrieve etc. The first grade teacher was frustrated. She bought new crayons, but soon they were broken into small pieces. She devised an experiment to show the students what was happening.