Matter and molecules

• Density is a measure of how much mass a substance of a certain volume has.
• Density (kg/m3 or g/cm3)= mass (kg)/ volume (m3 or cm3)
• Particles in a solid:

  In a fixed position and can’t flow

  They can‘t be compressed

  They vibrate around a fixed position

  They are in a regular arrangement and closely packed

  They have strong forces of attraction
• Particles in a liquid:

  They can flow and can’t be compressed

  They fill the bottom of a container

  They have a fixed volume

  Particles move in random directions at low speeds

  They are packed closely but in irregular arrangements

  They have weaker forces of attraction
• Particles in a gas:

  They can flow and fills a container

  Don’t have a fixed volume and can be compressed

  Particles move in random directions at high speeds

  They are far apart and have very weak forces of attraction
• Gas pressure increases as temperature increases because the particles gain more energy, so they collide with the walls of their container more frequently.
• The kinetic theory states that all matter is made of tiny particles. How they are arranged and move determines the properties of solids, liquids and gases.
• Solid to liquid= melting

  Solid to gas= sublimation

  Liquid to solid= freezing

  Liquid to gas= boiling/ evaporating

  Gas to liquid= condensing
• Internal energy is the total energy of the particles in a system, including the kinetic and potential energies.
• Specific latent heat is the amount of energy needed to change the state of 1kg of a substance without changing its temperature
• Latent heat of fusion is the amount of energy needed to melt or freeze the material at it’s melting point.
• Latent heat of vaporisation is the amount of energy needed to boil or condense the material at its boiling point. This uses more energy that fusion.
• Specific latent= the energy required for a particular change in state
• Specific heat capacity= the energy required for a particular change in temperature.
• Change in thermal energy= mass (kg) x specific latent heat (J/kg)
• You can increase the pressure of a container by:

  Reducing the containers volume, which causes more collisions with the wall of the container

  Adding more particles, which causes more collisions with the other particles

  Increasing the temperature, which increases the particle’s kinetic energy. This means collisions will exert more force more frequently.
• Boyle’s law states that for a fixed mass of gas at a constant temperature, pressure x volume= constant
• P1 x V1= P2 x V2
• Pressure is measured in Pa or kPa.
• Volume is inversely proportional to pressure.
• What state is the substance at letter A?

  Solid

  
• What state is the substance at letter B?

  Liquid

  
• What state is the substance at letter C?

  Gas

  
• Explain what is occurring at BC?

  The temperature of the liquid is rising until it reaches it’s boiling point at C.