My 10 yr old sister just asked me, I'm embarrassed that I don't know what she's on about, but it's in a quiz she was given for homework.
It'll either be seven or three. Because that's how these things work.
Does it mean physical change as in change between different states of matter? In that case: solid to liquid, liquid to solid, liquid to gas, gas to liquid, gas to solid, solid to gas...And then maybe you include plasma as a state? Ask in the physics subforum if I were you.
Edit: If it was for 10 year olds homework, then it won't be what I just said. So ignore that, I'm talking out of my bum hole.
Reversable and irreversable.
Well, all I could think of was puberty...
also, is making concrete a chemical change or physical change? I remember you mix sand with something..