Balloon popping when full of air and exposed to a flame but doesn't pop when water in the balloon.
https://www.youtube.com/watch?v=iCjauF7xS5Q&feature=fvw
Object at rest tends to stay at rest.
https://www.youtube.com/watch?v=uOSBC0SXVR4
Egg drop
https://www.youtube.com/watch?v=7Wn0KS_eWVc
Paper towels, inflated bag, breakfast cereal, foam rubber
Float Paper clips on water surface tension. Same principle as water spiders.
https://www.youtube.com/watch?v=9MBHf7j7bVs
Pulleys and ropes???
Centripetal Force
Spin a bucket around that has water in it.
Drop a ball and from different heights and predict how high the first bounce will be.
Gyroscope
Conductivity of different materials. Does it conduct or not?
Simple Motor: https://www.education.com/science-fair/article/no-frills-motor/
Colour Wheels and optical illusions.