1. States of Matter

• Solids

  • Solids have a fixed volume and shape and they have a high density.
  • The atoms vibrate in position but can’t change location
  • The particles are packed very closely together in a fixed and regular pattern
• Liquids

  • Liquids also have a fixed volume but adopt the shape of the container
  • They are generally less dense than solids (an exception is water), but much denser than gases
  • The particles move and slide past each other which is why liquids adopt the shape of the container and also why they are able to flow freely
• Gases 

  • Gases do not have a fixed volume, and, like liquids, take up the shape of the container
  • Gases have a very low density
  • Since there is a lot of space between the particles, gases can be compressed into a much smaller volume
  • The particles are far apart and move randomly and quickly (around 500 m/s) in all directions
  • They collide with each other and with the sides of the container (this is how pressure is created inside a can of gas)
• State changes

  • Melting
  • Boiling
  • Freezing
  • Evaporation
  • Condensation
  • Sublimation
• Melting

  • Melting is when a solid changes into a liquid
  • Requires heat energy which transforms into kinetic energy, allowing the particles to move
  • Occurs at a specific temperature known as the melting point (m.p.) 
• Boiling

  • Boiling is when a liquid changes into a gas
  • Requires heat which causes bubbles of gas to form below the surface of a liquid, allowing for liquid particles to escape from the surface and within the liquid
  • Occurs at a specific temperature known as the boiling point (b.p.)
• Freezing

  • Freezing is when a liquid changes into a solid
  • This is the reverse of melting and occurs at exactly the same temperature as melting, hence the melting point and freezing point of a pure substance are the same. Water, for example, freezes and melts at 0 ºC
  • Requires a significant decrease in temperature (or loss of thermal energy) and occurs at a specific temperature 
• Evaporation

  • Evaporation occurs when a liquid changes into a gas and occurs over a range of temperatures
  • Evaporation occurs only at the surface of liquids where high energy particles can escape from the liquid's surface at low temperatures, below the b.p. of the liquid
  • The larger the surface area and the warmer the liquid surface, the more quickly a liquid can evaporate
• Condensation

  • Condensation occurs when a gas changes into a liquid on cooling and it takes place over a range of temperatures
  • When a gas is cooled its particles lose energy and when they bump into each other they lack the energy to bounce away again, instead they group together to form a liquid
• Sublimation

  • Sublimation occurs when a solid changes directly into a gas
  • This only happens to a few solids, such as iodine or solid carbon dioxide
  • The reverse reaction also happens and is called desublimation or deposition
• A= Condensation

  B= Evaporation

  C= Sublimation

  D= Melting

  E= Freezing

  F= Desublimation

  
• The three states of matter are solids, liquids, and gases.