Topic 14 - Particle Model

• Solids


  Particles are tightly bound, very close, have a regular pattern, keep their shape, vibrate about a fixed point, lowest energy state
• Liquids


  Particles are still close but less tightly bound, have a more random arrangement, can be poured, particles move past each other, have more energy than solids, take the shape of their container
• Gases


  Particles are far apart, very few interactions between the particles, have a very low density, particles are randomly arranged, can be held in a closed container, move rapidly in all directions, have the highest energy state
• Density


  Mass divided by volume
• Measuring volume


  1. Regularly shaped object: measure dimensions with ruler or vernier caliper

  2. Irregularly shaped object: use measuring cylinder or displacement can
• Mass can be measured using a balance
• Digital instruments should be zero checked before use
• Irregularly shaped objects


  • Glass stopper
• Density of solids is usually highest, followed by liquids, then gases
• If density of an object is higher than water, it will sink, if lower, it will float
• Specific heat capacity


  Amount of energy required to raise the temperature of 1 kg of a substance by 1°C
• Measuring specific heat capacity of water


  Add 50 cm³ water to insulated cup, use lamp as heat source, measure temperature change, use formula: delta Q = m * c * delta theta
• Measuring specific heat capacity of copper


  Use 1 kg copper block and 12V electric heater, measure temperature change, use formula: delta Q = m * c * delta theta
• Specific heat capacity of water is around 200 J/kg°C, copper is around 385 J/kg°C
• Specific latent heat


  Amount of heat energy required to change the state of 1 kg of a substance without a temperature rise
• Measuring specific latent heat of vaporization of water


  Heat water at constant temperature, measure mass lost through evaporation, use formula: delta Q = delta m * L
• Specific latent heat of vaporization of water is 2260 kJ/kg
• Reducing heat transfer


  • Leslie's cube, thermos flask
• Pressure


  Result of collisions between gas particles and surface, increases with decreased volume or increased temperature
• Measuring relationship between pressure and volume of a gas

  Use piston apparatus, plot graph of pressure vs volume
• For a fixed mass of gas at constant temperature, pressure and volume are inversely proportional (p1*v1 = p2*v2)
• Compressing a gas increases its pressure and temperature