Select the true statement: Select one:
A. Bonds are broken and new bonds are formed during both chemical reactions and physical changes.

B. Bonds do not change in either chemical reactions or physical changes.

C. Bonds are broken and new bonds are formed during physical changes only.

D. Bonds are broken and new bonds are formed during chemical reactions only.

Atoms are the smallest particles of an element that can take part in a chemical reaction. During any chemical reaction no particles are created or destroyed: the atoms are simply rearranged from the reactants to the products. The products may have different properties to the reactants.
Mass is never lost or gained in chemical reactions. We say that mass is always conserved. In other words, the total mass of products at the end of the reaction is equal to the total mass of the reactants at the beginning.
This fact allows you to work out the mass of one substance in a reaction if the masses of the other substances are known.