Why can transferring energy into or out of a substance change the molecules' freedom of movement?

• A. Because energy affects the kinetic energy of molecules, allowing them to move more freely or become more restricted.
• B. Because energy transfer alters the chemical identity of the molecules.
• C. Because energy transfer increases the mass of the molecules.
• D. Because energy transfer changes the number of molecules in the substance.

Answer: (A)

Verified step by step guidance

1. Understand that the molecules in a substance are constantly in motion, and this motion is related to their kinetic energy.
2. Recognize that when energy is transferred into a substance (for example, by heating), it increases the kinetic energy of the molecules, causing them to move more rapidly and freely.
3. Conversely, when energy is transferred out of a substance (for example, by cooling), the kinetic energy of the molecules decreases, making their movement more restricted.
4. Note that this change in molecular motion does not alter the chemical identity, mass, or number of molecules; it only affects how they move.
5. Therefore, the freedom of molecular movement is directly linked to the amount of kinetic energy the molecules possess, which is controlled by energy transfer.