Which of the following best defines energy, and which is an example of energy on a small scale?

• A. Energy is the ability to do work; an example on a small scale is the vibration of molecules in a substance.
• B. Energy is the rate at which a reaction occurs; an example on a small scale is the speed of a chemical reaction.
• C. Energy is the volume occupied by a substance; an example on a small scale is the space inside a molecule.
• D. Energy is the amount of matter in an object; an example on a small scale is the mass of an atom.

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the definition of energy in the context of chemistry. Energy is commonly defined as the ability to do work or cause change, which is fundamental to chemical processes.
2. Step 2: Recognize examples of energy on a small scale. In chemistry, molecular vibrations, rotations, and movements represent forms of energy at the microscopic level.
3. Step 3: Evaluate each option by comparing its definition of energy to the accepted scientific definition. For example, 'energy is the rate at which a reaction occurs' actually describes reaction rate, not energy.
4. Step 4: Identify which example corresponds to energy on a small scale. Vibrations of molecules represent kinetic energy at the molecular level, making it a valid example.
5. Step 5: Conclude that the best choice is the one that correctly defines energy as the ability to do work and gives molecular vibration as an example of energy on a small scale.