Which of these is common to all chemical changes?

a)
a change of state occurs.

b)
a change of color occurs.

c)
a new substance is produced.

d)
heat is released into the air.

Option (C) is the correct answer.

Explanation:

A chemical change is a change which brings change in chemical composition of a substance or reactant(s).

Thus, we can say the due to change in composition we get a new product.

For example,

That is, NaCl is the new product formed.

Hence, we can conclude that common to all chemical changes is that a new substance is produced.  

the atomic mass is the bottom number on the element.

-steel jelly