Chapter 1: States of Matter

• Solids


  Have a fixed volume and shape, high density
• Solids


  • Atoms vibrate in position but can't change location
  • Particles are packed very closely together in a fixed and regular pattern
• Liquids


  Have a fixed volume but adopt the shape of the container, generally less dense than solids
• Liquids


  • Particles move and slide past each other, allowing liquids to adopt the shape of the container and flow freely
• Gases


  Do not have a fixed volume, take up the shape of the container, very low density
• Gases


  • Lots of space between particles, can be compressed into a much smaller volume
  • Particles are far apart and move randomly and quickly (around 500 m/s) in all directions
  • Particles collide with each other and with the sides of the container (this is how pressure is created inside a can of gas)
• Melting


  When a solid changes into a liquid
• Melting


  1. Requires heat energy which transforms into kinetic energy, allowing the particles to move

  2. Occurs at a specific temperature known as the melting point (m.p.)
• Boiling


  When a liquid changes into a gas
• Boiling


  1. 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

  2. Occurs at a specific temperature known as the boiling point (b.p.)
• Freezing


  When a liquid changes into a solid
• Freezing


  1. 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

  2. Requires a significant decrease in temperature (or loss of thermal energy) and occurs at a specific temperature
• Evaporation


  When a liquid changes into a gas and occurs over a range of temperatures
• Evaporation


  1. 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

  2. The larger the surface area and the warmer the liquid surface, the more quickly a liquid can evaporate
• Condensation


  When a gas changes into a liquid on cooling and it takes place over a range of temperatures
• Condensation


  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


  When a solid changes directly into a gas
• Sublimation only happens to a few solids, such as iodine or solid carbon dioxide
• The reverse reaction of sublimation is called desublimation or deposition
• Kinetic theory of matter


  When substances are heated, the particles absorb thermal energy which is converted into kinetic energy
• Heating a solid


  1. Particles vibrate more

  2. As temperature increases, particles vibrate so much that the solid expands

  3. Structure breaks and the solid melts
• Heating a liquid


  1. Liquid substance expands more

  2. Some particles at the surface gain sufficient energy to overcome the intermolecular forces and evaporate

  3. When the b.p. temperature is reached, all the particles gain enough energy to escape and the liquids boils
• Heating curve


  Graph used to show how changes in temperature affect changes of state
• Cooling curve


  Reverse effect of heating curve when cooling down a gas
• The horizontal sections on the curves occur when there is a change of state but there is no change in temperature
• A change in temperature or pressure


  Affects the volume of gases
• As the air inside a hot air balloon is heated up


  It expands and the balloon gets bigger
• The volume of a gas increases as its temperature increases
• As temperature increases


  Gas volume increases
• As the volume increases


  The density decreases so the balloon rises
• If you have a gas stored inside a container that is squeezed

  The pressure increases as you decrease the volume
• This is what happens in a bicycle pump

  • As you compress the bicycle pump the high pressure allows you to inflate a tire
  • You can feel the force of the high pressure if you put your finger on the end of the pump
• As volume decreases in a bicycle pump


  Pressure increases
• Gaseous particles


  • In constant and random motion
  • The pressure that gas creates inside a closed container is produced by the gaseous particles hitting the inside walls of the container
• As temperature increases


  The kinetic energy of each particle increases as the heat energy is transformed to kinetic energy, so they move faster
• As the temperature increases


  The particles in the gas move faster, impacting the container's walls more frequently
• If the container walls are flexible and stretchy

  The container will get bigger and bigger, just like the hot air balloon!
• If the container is made smaller


  The gas particles hit the wall more frequently, causing an increase in gas pressure
• Diffusion


  The process by which different gases or different liquids mix and is due to the random motion of their particles
• Diffusing particles move from an area of high concentration to an area of low concentration