States of matter

In short: Substances exist as solid, liquid or gas. The state depends on temperature and pressure because the bonds between particles change.

In more detail: In solids the particles sit in fixed places, in liquids they slide past each other, in gases they move largely freely.

In detail

• Transitions: Melting (solid → liquid), freezing, evaporating, condensing, sublimating (solid → gas, such as dry ice), deposition.
• Water: Freezes at 0 °C, boils at 100 °C at sea level. On mountains it boils earlier because air pressure is lower (luftdruck-und-wetter).
• Evaporative cooling: Evaporation removes heat. That is why sweating cools.
• Plasma: A fourth state at very high temperatures, for example in lightning and the Sun.
• Water anomaly: Ice is lighter than liquid water and floats.