Particle model of matter

• Describe the particle arrangement of a solid:

  Tightly packed in a regular arrangement

  Particles can only vibrate on the spot

  Low kinetic energy
• Describe the particle arrangement of a liquid:

  Flow around eachother, irregular arrangement

  Close together

  More kinetic energy than a solid
• Describe the particle arrangement of a gas:

  Separated, irregular arrangement

  Particles can move freely in random directions at varying speeds

  High kinetic energy
• What is conserved when a substance undergoes a change of state?

  Mass
• What is sublimation?


  The process of a substance changing directly from a solid to a gas without going through the liquid phase
• What is evaporation?


  Liquid to Gas
• What is condensation?


  Gas to Liquid
• What is the internal energy of a substance?


  > The energy stored by the particles

  > The sum of the total kinetic and potential energies that make up the system
• How does heating affect the energy of a substance?

  > Heating transfers energy to the substance

  > It increases the energy of the particles that make up the substance
• What 3 factors determine the temperature change of a system?

  Mass of substance

  Material (specific heat capacity)

  Energy inputted into the system
• Define specific heat capacity:

  The amount of energy needed to increase the temperature if 1kg of a substance by 1 degree c
• Describe how the internal energy and temperature of a substance changes when a change of state occurs

  > The internal energy of the substance will be increased or decreased

  > The temperature of the substance will remain constant
• Define specific latent heat:

  The amount of energy needed to change the state of 1kg of a substance with no change in temperature
• What is the specific latent heat of fusion?

  The energy required to change 1kg of a substance from solid to liquid without a change in temp
• What is the specific latent heat of vaporisation?

  The energy required to change 1kg of a substance from liquid state to gas state (vapour) without a change in temperature
• What effect does increasing temperature have on the pressure of a gas when held at constant volume

  Pressure of the gas will increase as the temperature increases
• Why does pressure increase as temperature increases (at a constant volume)

  > Kinetic energy of molecules increases

  > Collisions between molecules becomes more frequent

  > Greater rate of change of momentum

  > Greater force and therefore pressure
• Describe the force that the pressure of a gas exerts on the walls of its container:

  > The net force acts at right angles to the container’s surface

  > The force increases as pressure increases
• Explain how increasing the volume of a gas results in a decrease of pressure:

  > Molecules become more spread out and so time between collisions increases

  > This reduces the rate of collisions

  > The rate of change of momentum decreases and so force exerted on contained decreases, resulting in a lower pressure
• Why does the temperature of air inside a bike pump increase when it is pumped?

  > Work is done on a gas when it is compressed

  > Doing work on a gas increases its internal energy so also increases the average kinetic energy of the molecules

  > Temperature increases with an increase of average kinetic energy