As the molecular motion of a substance increases, which of the following changes occurs?

• A. The mass of the substance increases.
• B. The temperature of the substance increases.
• C. The substance becomes less energetic.
• D. The chemical identity of the substance changes.

Answer: (B)

Verified step by step guidance

1. Understand that molecular motion refers to the movement of particles (atoms or molecules) within a substance, which is related to the kinetic energy of those particles.
2. Recall that temperature is a measure of the average kinetic energy of the particles in a substance, so as molecular motion increases, the average kinetic energy and thus the temperature increases.
3. Recognize that the mass of the substance does not change with molecular motion because mass is a measure of the amount of matter, which remains constant unless matter is added or removed.
4. Note that increasing molecular motion means the substance becomes more energetic, not less, because kinetic energy is increasing.
5. Understand that the chemical identity of the substance remains the same during changes in molecular motion, as chemical identity changes only occur through chemical reactions, not physical changes like temperature increase.