Science
What is Solid?
A solid is a state of matter with a fixed shape and volume. Its particles are packed closely together in a regular arrangement and can only vibrate in place, which is why a solid holds its form instead of flowing or spreading out.
See it, don’t just read it.
Watch a 2-minute lesson with voice + animation that explains solid.
Key things to understand
- 1A solid keeps both its shape and its size — it doesn't flow or expand to fill a container.
- 2Its particles are tightly packed and locked in position, vibrating but not moving past each other.
- 3Because the particles are so close, solids are usually very hard to compress.
- 4Heating a solid enough makes its particles vibrate so much that it melts into a liquid.
- 5Solids can be crystalline (orderly, like salt) or amorphous (jumbled, like glass).
Frequently asked questions
- Why does a solid keep its shape?
- Its particles are held tightly in fixed positions by strong forces, so they can only vibrate in place — they can't slide past one another to let the solid flow.
- What happens when a solid is heated?
- The particles gain energy and vibrate harder. Heat it enough and they break free of their fixed positions, and the solid melts into a liquid.
- Are all solids hard?
- No. Rubber and wax are solids too. What makes something a solid is its fixed shape and volume, not how hard it feels.