Question

If a chemical reaction takes place, what must change?

Answer 1

In a chemical reaction, the structure of one or more molecules must be changed.

Explanation:

This is the chief characteristic of a chemical reaction - molecules are broken apart and new molecules made from the atoms.

In a physical change, all that happens is the relative positions of the molecules is altered - the pattern of a solid crystal broken up as it melts, or molecules moving to great separations during boiling - but the structure of the molecules themselves is unchanged.

Answer 2

• concentratio of reactant and product.

Explanation:

When a chemical reaction takes place, the mass or concentration of whole reaction remain same but the concentration of reactant decrease and concentration of product increase .