What occurs during phase changes in terms of energy?

What occurs during phase changes in terms of energy?

• A. Energy is conserved and not transferred
• B. Energy is absorbed or released, changing molecular interactions
• C. Energy is only released, never absorbed
• D. Molecular interactions remain unchanged while overall temperature increases

Answer: (B)

During phase changes, energy is indeed absorbed or released, leading to changes in molecular interactions. When a substance transitions from one phase to another—such as from solid to liquid (melting) or liquid to gas (vaporization)—energy must be added to the system to overcome the intermolecular forces holding the particles together. Conversely, during processes such as condensation or freezing, energy is released as the particles lose kinetic energy and come closer together, strengthening the interactions between them. This absorption or release of energy is essential because it directly influences the state of the substance and the arrangement and movement of its molecules. For example, in melting, energy absorbed allows the rigid structure of a solid to break down, leading to the more fluid arrangement of a liquid. Hence, the correct understanding of phase changes involves recognizing that these energy transfers are crucial to altering molecular interactions and resulting in the observed physical state changes.

During phase changes, energy is indeed absorbed or released, leading to changes in molecular interactions. When a substance transitions from one phase to another—such as from solid to liquid (melting) or liquid to gas (vaporization)—energy must be added to the system to overcome the intermolecular forces holding the particles together. Conversely, during processes such as condensation or freezing, energy is released as the particles lose kinetic energy and come closer together, strengthening the interactions between them.

This absorption or release of energy is essential because it directly influences the state of the substance and the arrangement and movement of its molecules. For example, in melting, energy absorbed allows the rigid structure of a solid to break down, leading to the more fluid arrangement of a liquid. Hence, the correct understanding of phase changes involves recognizing that these energy transfers are crucial to altering molecular interactions and resulting in the observed physical state changes.