Answer:
- option a. <em><u>energy can be gained or lost.</u></em>
Explanation:
<em>Energy can be gained or lost in both physical and chemical changes.</em>
Most physical changes involve energy gain or loss. For example:
- Melting: for a substance to change from solid to liquid, the substance has to gain energy to increase the kinetic energy of the particles and they can overcome the forces of attraction and separate.
Similar reasoning can be made about freezing, evaporation, condensation, and many other physical changes.
As per chemical changes, in order to the reactant substances break their bonds energy must be gained, and as new bonds are formed to constitute the product substaces energy is loss. The net change of energy will tell if the reaction is endothermic (net gain of energy) or exothermic (net release or loss of energy).
In order to meet the energy conservation law, the energy that is gained or lost by a substance is lost or gained by other substance.
As per the options b. and c. the law of conservation of mass states that energy can be never be created or destroyed, so those options are incorrect.
