Which state of matter has a definite volume but no definite shape?

• A. Solid
• B. Liquid
• C. Gas
• D. Plasma

Answer: (B)

The key idea is how particle movement determines whether a substance keeps its volume and/or shape. Liquids hold a definite volume because their particles are close together and flow past one another, so they don’t compress or spread out to fill a container’s volume. But they don’t keep a fixed shape; they flow to match the container, taking on its shape rather than a fixed form. Solids, in contrast, keep both a definite shape and volume because their particles are tightly packed and vibrate in place. Gases have neither fixed shape nor fixed volume since their particles are far apart and spread to fill the space available. Plasmas behave similarly to gases at high energy. So the state with definite volume but no definite shape is a liquid.