Interpreting Heating and Cooling Graphs with Change of State

Key Concepts

• Internal Energy: Energy stored inside a system by the particles, including:
  • Kinetic Energy: Due to movement of particles.
  • Potential Energy: Due to forces between particles and bonds between atoms in a molecule.

Heating Graphs

• Temperature Increase: When heating a solid, the temperature rises as energy in particles increases.
• Change of State (Melting):
  • Temperature stops rising and the graph becomes horizontal.
  • The solid changes to a liquid (melting).
  • Energy input weakens/breaks forces between particles.
  • Latent Heat: Energy needed for a substance to change state. (To be covered in detail later)
  • During a change of state, internal energy increases but temperature remains constant.
  • Melting Point: Temperature at which the substance melts, identifiable on the graph.
• Temperature Rises Again: Post-melting, temperature continues to rise as energy continues to increase.
• Boiling:
  • Temperature plateaus again, indicating boiling.
  • Energy breaks forces of attraction between particles.
  • Boiling Point: Can be determined from the graph.

Cooling Graphs

• Gas Cooling: A cooling graph shows temperature decrease of a gas.
• Change of State:
  • Condensation: Gas changes to liquid.
  • Freezing: Liquid changes to solid.

Study Resources

• Heating and cooling graphs questions are available in the revision workbook.
• Workbook accessible via a provided link.

Conclusion

• Ability to interpret heating and cooling graphs that include change of state.