Which of the following is typically required to cause a substance to change phases (for example, from solid to liquid or liquid to gas)?

• A. Increasing the volume of the container without changing temperature or pressure
• B. Changing the color of the substance
• C. Mixing the substance with water
• D. Adding or removing energy, usually in the form of heat

Answer: (D)

Verified step by step guidance

1. Understand that a phase change involves a substance transitioning between solid, liquid, and gas states.
2. Recognize that phase changes require energy to overcome intermolecular forces holding the particles together in one phase.
3. Identify that this energy is typically added or removed as heat, which changes the internal energy of the substance without necessarily changing temperature during the phase change.
4. Note that simply increasing the volume of the container, changing color, or mixing with water does not directly cause a phase change unless energy is added or removed.
5. Conclude that the key requirement for a phase change is the addition or removal of energy, usually in the form of heat.