Question

Which is true about law of conservation of mass?

A. when a new substance is formed, matter is added
B. Atoms are destroyed during a chemical reaction
C. During a chemical reaction, atoms are created
D. Atoms cannot be created or destroyed, only rearranged

Answer 1

D. Atoms cannot be created or destroyed, only rearranged.

The law of conservation of mass states that in a closed system, the mass of reactants must equal the mass of products in a chemical reaction. This means that atoms are conserved; they are only rearranged to form new substances.

Answer 2

What happens to water as it evaportates?
A. atoms are added
B. it becomes less dense water vapor
C. A new substance is formed
D. Atoms are destroyed

Answer 3

B. it becomes less dense water vapor.

When water evaporates, it transitions from a liquid state to a gaseous state, becoming water vapor. This process does not involve the addition of atoms or the formation of a new substance, and atoms are not destroyed; they simply change state. The water vapor is less dense than liquid water.