Pressure Cooker

This may be an early concept to completely understand, but, for the basic part for toddlers, it is never too early, never too late.

Just keep talking, keep explaining and observe how keen your child is when listening and learning stuff.

The main concept of pressure cooker is to create and sustain pressure for boiling, The heat generated within pressure cooker along with great pressure gets the cooking done efficiently.
And then, it has something called as whistle, that expels excess pressure.