topic 14

• 14.1 Use a simple kinetic theory model to explain the different states of matter (solids, liquids and gases) in terms of the movement and arrangement of particles - solids


  - Particles are arranged in rows (in a regular arrangement).

  - Particles vibrate about fixed point.

  - There are forces of attraction between particles but don't have enough energy to overcome the forces of attraction.
• 14.1 Use a simple kinetic theory model to explain the different states of matter (solids, liquids and gases) in terms of the movement and arrangement of particles - liquids


  - Particles are randomly arranged.

  - Particles can move around each other.

  - Particles have more energy than solids and can therefore overcome the forces of attraction.

  - Do not have enough energy to sufficiently overcome attractive forces completely.

  - No fixed shape but take the shape of the container.
• 14.1 Use a simple kinetic theory model to explain the different states of matter (solids, liquids and gases) in terms of the movement and arrangement of particles - gases


  - Particles arranged randomly and far apart.

  - Sufficient energy to overcome forces of attraction completely.

  - Particles are moving quickly in all directions.
• 14.2 Recall and use the equation: density (kilogram per cubic metre, kg/m3) = mass (kilogram, kg) ÷ volume (cubic metre, m3)


  density = mass ÷ volume
• 14.3 Core Practical: Investigate the densities of solid and liquids
• 14.4 Explain the differences in density between the different states of matter in terms of the arrangements of the atoms or molecules

  Most substances are the most dense when they are in solid form and the least dense when they are in a gaseous form.

  
  

  This is due to the arrangement of the molecules; with solids' molecules being closer together and gases being far apart.
• 14.5 Describe that when substances melt, freeze, evaporate, boil, condense or sublimate mass is conserved and that these physical changes differ from some chemical changes because the material recovers its original properties if the change is reversed

  When substances melt, freeze, evaporate, boil, condense or sublimate, mass is conserved.

  
  

  These physical changes differ from some chemical changes because the material recovers its original properties if the change is reversed.
• 14.6 Explain how heating a system will change the energy stored within the system and raise its temperature or produce changes of state


  Heating a system will cause the energy stored within the system will change and raise its temperature as heating a system causes thermal energy to be stored. The more energy being stored means the speed of the vibrating particles increases.

  
  

  If enough energy is being stored, the particles vibrate fast enough in order to break the molecular forces between particles, causing changes in state.

  
  

  * Temperature is a measure of the movement of particles.
• Temperature


  Temperature is a measure of the movement of particles.
• 14.7 Define the terms specific heat capacity and specific latent heat and explain the differences between them - specific heat capacity

  Specific heat capacity is the amount of energy it takes to increase the temperature of 1°C of the substance of 1 kilogram.
• 14.7 Define the terms specific heat capacity and specific latent heat and explain the differences between them - specific latent heat

  Specific latent heat is the amount of energy it takes to make 1 kilogram of a substance change state.
• 14.7 Define the terms specific heat capacity and specific latent heat and explain the differences between them - differences

  - Specific heat capacity measures the change in temperature, whereas specific latent heat is the change in state.

  
  

  - Specific heat causes temperature change where in latent heat there's no temperature change involved.

  
  

  - Latent heat is the amount of energy in joules and specific heat is the quantity of heat measured in degrees Celsius.
• 14.8 Use the equation: change in thermal energy (joule, J) = mass (kilogram, kg) × specific heat capacity (joule per kilogram degree Celsius, J/kg °C) × change in temperature (degree Celsius, °C)


  change in thermal energy = mass x specific heat capacity x change in temperature
• 14.9 Use the equation: thermal energy for a change of state (joule , J) = mass (kilogram, kg) × specific latent heat (joule per kilogram, J/kg)


  thermal energy for a change of state = mass x specific latent heat
• 14.10 Explain ways of reducing unwanted energy transfer through thermal insulation

  To reduce the amount of energy that is transferred to the surroundings by heating, the object needs to be surrounded with insulating materials such as:

  - wool

  - foam

  - bubble wrap

  
  

  It prevents any more thermal energy from being transferred.
• 14.11 Core Practical: Investigate the properties of water by determining the specific heat capacity of water and obtaining a temperature-time graph for melting ice
• 14.12 Explain the pressure of a gas in terms of the motion of its particles

  The pressure of a gas is due to the forces on the walls of a container causing by moving particles hitting the walls.

  
  

  The faster the particles are moving, the more collisions there will be and more force exerted.
• 14.13 Explain the effect of changing the temperature of a gas on the velocity of its particles and hence on the pressure produced by a fixed mass of gas at constant volume (qualitative only)


  For a fixed mass of gas at a constant volume, increasing the temperature of the gas increases the velocity of the particles so increases the pressure of the gas.
• 14.14 Describe the term absolute zero, −273 °C, in terms of the lack of movement of particles


  The temperature at which the pressure of a gas drops to zero, and the particles would not be moving.

  
  

  -273°C or 0K
• 14.15 Convert between the kelvin and Celsius scales

  Kelvin to Celsius = subtract 273

  
  

  Celsius to Kelvin = add 273
• 14.16P Explain that gases can be compressed or expanded by pressure changes

  If you increase the pressure of a gas, it can be compressed.

  
  

  If you decrease the pressure of a gas, it can be expanded.
• 14.17P Explain that the pressure of a gas produces a net force at right angles to any surface


  The effect of gas particles hitting a surface causes a net (overall) force on the surface. The force acts at right angles to the surface; this is gas pressure.
• 14.18P Explain the effect of changing the volume of a gas on the rate at which its particles collide with the walls of its container and hence on the pressure produced by a fixed mass of gas at constant temperature

  Decreasing the volume of a fixed mass of gas at constant temperature on the rate at which its particles collide with walls increasing the pressure produced.

  
  

  And increasing the volume, decreasing the pressure produced.
• 14.19P Use the equation: P1 ×V1 = P2 ×V2 to calculate pressure or volume for gases of fixed mass at

  constant temperature

  P^1 x V^1 = P^2 X V^2
• 14.20P Explain why doing work on a gas can increase its

  temperature, including a bicycle pump

  When you use a bicycle pump, the work done force is transferring energy to gas inside the pump.

  
  

  With every pump, the speed of the particles increases, and this is detected as an increase in temperature.