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Year 7 & 8 TOC

Water in nature

States of water

LO: Considering the water cycle in terms of changes of state of water

As you have already learnt, substances can exist in different states: Solid, liquid and gas. Water is no exception. 


  • When water freezes and becomes ice, the point at which it freezes is called it’s freezing temperature.
  • The water molecules loose energy and eventually stop moving and vibrate on the spot. 
  • Once something is solid (like ice) it’ll hold it’s shape even when poured out. 


  • As we heat ice up, it will eventually melt. The point at which it melts is called it’s melting point. 
  • As something heats up, the water molecules begin to move.
  • A liquid is flexible and can flow into and over things. 


  • If we keep heating the liquid up, it’ll eventually evaporate and turn to water vapour. The temperature that gas starts to form is called its ‘boiling point’.
  • As we add more heat, the water molecules begin to move even more quickly and further apart. They end up moving so quickly they can separate themselves from the rest of the liquid. 
  • Gas can’t sit in a container, but instead it moves around the container. 

All substances have these different points where they change states. Iron becomes a liquid (melting point) at 1535 °C and turns to a vapour (boiling point) at 2750 °C! 

Scientists have always been looking at the stars in search for new planets and life, far beyond our own solar system. In 2017 scientist discovered a planet which is hot enough to turn metal into gas! The planet is called KELT-9b and it’s a gas giant with the designation of “ultra-hot Jupiter”. It’s located 650 light years from Earth and it’s atmospheric temperature is over 4000°C! That’s enough to turn iron and titanium into vapour!!


  • If we want to turn the gas back to a liquid we decrease the temperature. This process is called condensation. 
  • Here we are removing heat from the water, slowing down the molecules and turning it back into a liquid. 

From boiling to freezing

If you live in a snowy super cold place you can take a pot of boiling water and change it’s state instantly! Check out the video below. This has to do with water’s ability to change states. 

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