Pressure is an intensive physical size defined as the ratio between the form of the force acting orthogonally on a surface and its area.
If you explain the pressure in this way your son will not only be bored but he also won't learn anything.
Take a bowl, some water, a candle and a glass bottle.
Watch the video to find out what's going on and how 壓力 is coming.
You will be amazed and you will be able to replicate this 實驗 to teach your children how the pressure works.
What are you waiting for? Prepare everything you need to teach your children how the pressure works and amaze them so much that they will learn and create the right curiosity in them.