Which of the following are the three states of matter?

• A. Solid, liquid, gas
• B. Solid, liquid, plasma
• C. Fluid, solid, gas
• D. Gas, liquid, vapor

Answer: (A)

The three states of matter are solid, liquid, and gas. Solids have a fixed shape and volume because their particles are closely packed together and vibrate in place. Liquids take the shape of their container while maintaining a constant volume since their particles are close but can move around each other freely. Gases, on the other hand, have neither a fixed shape nor a fixed volume; their particles are far apart and move quickly, filling the space of their container.

Recognizing that the other choices include combinations that either substitute one of the fundamental states or include variations of states, such as plasma (which is a distinct state of matter but not one of the three primary states), helps clarify why solid, liquid, and gas is the correct set to identify the three basic states of matter.