States of Matter

All the matter around you exists in different states depending on temperature and pressure. The three states you see every day are solid, liquid and gas. Water is the perfect example: ice is the solid state, water is the liquid state, steam is the gas state. There is also a fourth state called plasma (super-heated gas with electric charge) which makes up most of the visible universe, and rare extra states like Bose-Einstein condensate that only exist in laboratories near absolute zero. The differences between states come from how tightly the particles are packed together and how much they move.

• Everyday states3Solid, liquid, gas
• Plus plasma4th stateMost common in the universe
• Plus Bose-Einstein condensate5th stateOnly near absolute zero
• Solid particlesTightly packedVibrate in place
• Liquid particlesClose but movingFlow around each other
• Gas particlesFar apart, fastFill any container

The three everyday states

• Solid: particles are packed tightly together in a fixed shape. They vibrate in place but cannot easily move past each other. Solids keep their shape and volume. Examples: ice, wood, metal, stone.
• Liquid: particles are still close but can move past each other. Liquids take the shape of their container but keep a fixed volume. Examples: water, oil, blood, mercury.
• Gas: particles are far apart and zoom around freely. Gases expand to fill any container they are in. Examples: air, steam, oxygen, helium.

How states change

Adding or removing energy (usually heat) changes matter from one state to another.

• Melting: solid to liquid. Ice melts into water at 0 degrees C.
• Freezing: liquid to solid. Water freezes into ice at 0 degrees C.
• Evaporation/Boiling: liquid to gas. Water boils into steam at 100 degrees C.
• Condensation: gas to liquid. Steam condenses into water on a cold mirror.
• Sublimation: solid directly to gas, skipping the liquid stage. Dry ice (frozen CO2) sublimates straight to gas at -78 degrees C.
• Deposition: gas directly to solid, also skipping liquid. Frost forms on windows this way.

The fourth state: plasma

Plasma is what happens when you heat a gas so much that the atoms break apart into separate positive ions and free electrons. Plasma can carry electricity and respond to magnetic fields, behaving very differently from ordinary gas. Despite being almost unknown on the surface of Earth, plasma is actually the most common state of matter in the universe: stars, the Sun and most of the visible universe are plasma.

You can see plasma on Earth in:

• Lightning bolts.
• The flames of a fire (partial plasma).
• Neon signs and fluorescent light tubes.
• Plasma TVs (now mostly obsolete).
• The northern and southern lights (auroras).
• The Sun and every other star.

Fact Bose-Einstein condensate is a remarkable fifth state of matter that only exists when you cool a gas to within a tiny fraction of a degree above absolute zero (minus 273 degrees C). At those temperatures, the atoms stop behaving as individuals and merge into a single quantum state, where they all act like one giant atom. The state was predicted in 1924 by Einstein and Indian physicist Satyendra Bose, but only created in a lab in 1995. The scientists who made it won the Nobel Prize in 2001.

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