Cooling and Heating Graphs

• Heating


  Energy is transferred to the substance and the kinetic energy of the molecules increases (red arrows to the right)
• Cooling


  Energy is transferred away from the substance (dissipated to the surroundings) and the kinetic energy of the molecules decreases (blue arrows to the left)
• Heating a solid


  1. Temperature starts to increase as the particles gain kinetic energy and vibrate faster

  2. When temperature reaches melting point, energy is used to overcome intermolecular forces holding particles in solid structure

  3. Temperature stops increasing

  4. Melting continues until all particles reach liquid state

  5. As energy is added, temperature of liquid increases as particles gain more kinetic energy and move faster
• Heating a liquid


  1. When temperature reaches boiling point, energy is used to overcome intermolecular forces holding particles in liquid structure

  2. Temperature stops increasing

  3. Evaporation or vaporisation continues until all particles reach gaseous state
• Cooling a gas


  1. Temperature starts to decrease as particles lose kinetic energy and move slower

  2. When temperature reaches boiling point, energy is taken from that used to overcome intermolecular forces

  3. Temperature stops decreasing

  4. Condensation continues until all particles reach liquid state
• Cooling a liquid


  1. Temperature starts to decrease as particles lose more kinetic energy and move even slower

  2. When temperature reaches melting point, energy is taken from that used to overcome intermolecular forces

  3. Temperature stops decreasing

  4. Freezing continues until all particles reach solid state