okay can someone explain what conservation of mass is to me? my teacher told us but wasn't clear. i had a test with it in today so i want to know so i can tell my teacher i do understand it now.
Conservation of mass merely states that the total mass is conserved (stays the same) in any physical or chemical process.
It is not true in nuclear reactions. Mass can be converted to energy and vice versa.
Actually, although your science teacher my not be aware of it, mass is not exactly conserved in chemical reactions either. There is a conversion of mass to energy even in chemical reactions, but it is too low to measure.