Heat and thermal energy

• Particles


  • All matter is made of particles that are constantly moving.
  • Different states of matter have different physical properties.
  • Properties depend on bonds between particles.
• Particle model


  • Used to explain the properties of solids, liquids and gases

  
• Number of bonds and particle speed

  • Determined by the amount of heat that particles have
  • When particles have more energy, the faster they will move and the more bonds can break
  • Particles with more energy have fewer bonds
• Solid particles


  • Have low energy
  • Bonds between particles don't break easily
  • Particles stay close together
  • Particles vibrate and form solid shapes
• Liquid Particles


  • Have enough energy to break some bonds
  • Particles can move around but still stay close together
  • The particles form liquids that take the shape of their container
• Gas Particles

  • Have lots of energy
  • All bonds can break
  • Particles move freely, allowing them to fill their container
• Thermal energy


  • Kinetic energy refers to the energy of any object in motion
  • Thermal energy is a type of kinetic energy objects possess due to the movement of particles (vibrate/moving)
  • Thermal energy can be transferred from one object to another as heat - heat transfer
• Heat Transfer


  • The movement of heat from one object to another or from one place to another
  • Heat always flows from a hotter object to a colder object (moving down the temperature gradient) until equilibrium is reached (both objects are the same temperature)
  • Heat transfer occurs faster with a larger temperature difference
• Heat vs Temperature

  • Heat is a type of energy (Thermal energy). It's the sum of the kinetic energy of particles in a substance and is measured on joules (J)
  • Temperature is the average kinetic energy of particles in a substance. Measured in degrees Celsius (°C)
• Why does a pot of boiling water have less heat than a massive iceberg even though it has a higher temperature?

  • This is because the iceberg has more particles than the pot of boiling water.
  • When you add the kinetic energy of all these particles, you get a larger number and therefore more heat.
  • However, the average kinetic energy of the iceberg particles is less than that of particles in the boiling water.
  • This means that the iceberg is at a lower temperature than the boiling water