The law of conservation of mass basically means no atoms are created or destroyed.
This means in a chemical reaction the mass of the PRODUCTS will ALWAYS equal the mass of the REACTANTS
So during reactions atoms are rearranged into different chemicals - chemicals are not 'used up'
It's significant as if scientists know the identities and quantities of reactants for a reaction, they can predict the amount of products that will be made.
Matter is a substance and the three types are solid liquid and gas
8N - 6cm
10N - 7.5cm
14N - 10.5cm