What Are the States of Matter?
Solids, liquids, gases, and plasma — why everything around you takes the form it does.
Everything Is Made of Particles
Look around you. Your desk, the air you're breathing, the water in your glass — they're all made of incredibly tiny particles (atoms and molecules) that are always moving. The difference between a solid, a liquid, and a gas isn't what the particles are made of — it's how fast they're moving and how close together they are.
Temperature is the key. When you add heat energy to matter, particles move faster. When you remove heat, they slow down. This relationship between temperature and particle movement is what creates the three main states of matter.
Solids: Particles Locked in Place
In a solid, particles are packed tightly together in a fixed pattern. They vibrate in place but don't move around. This is why solids have a definite shape and a definite volume — a rock stays rock-shaped whether you put it on a table or in a box. The strong attractions between particles keep everything locked in position.
Think of particles in a solid like students sitting in assigned seats. They can wiggle and shift, but they stay in their spots.
Liquids: Particles That Slide
Add enough heat to a solid and the particles start moving fast enough to break free from their fixed positions. Now they can slide past each other while still staying relatively close together. This is a liquid. Liquids have a definite volume but no definite shape — they take the shape of whatever container holds them. Pour water into a round glass, and it becomes round. Pour it into a square container, and it becomes square.
Particles in a liquid are like students at a school dance: moving around the room, bumping into each other, but staying inside the gymnasium.
Gases: Particles Set Free
Add even more heat and particles move so fast they completely break free from each other. In a gas, particles spread out to fill whatever space is available. Gases have no definite shape and no definite volume. Open a bottle of perfume, and the gas molecules spread across the entire room. That's because gas particles move in every direction at high speed, bouncing off walls and each other.
Phase Changes: Transforming Between States
When matter changes from one state to another, it's called a phase change. These changes happen at specific temperatures for each substance:
- Melting — solid → liquid (ice melts at 0°C / 32°F)
- Freezing — liquid → solid (water freezes at 0°C / 32°F)
- Evaporation/Boiling — liquid → gas (water boils at 100°C / 212°F)
- Condensation — gas → liquid (steam on a cold mirror)
- Sublimation — solid → gas directly (dry ice turning to fog)
During a phase change, the temperature stays constant even though you're adding heat. All the energy goes into breaking the bonds between particles rather than making them move faster. That's why ice water stays at exactly 0°C until all the ice has melted — the heat is busy breaking bonds, not raising temperature.
There's actually a fourth state of matter called plasma. It forms when gas gets so hot that electrons are stripped away from atoms. Plasma makes up over 99% of the visible universe — stars (including our Sun), lightning bolts, and neon signs are all plasma. It's the most common state of matter in the universe, even though it's the rarest on Earth's surface.
Last reviewed: April 2026