Internal Energies

• Internal energy


  The total energy stored inside a system by the particles that make up the system due to their motion and positions
• Energy stores of molecules in a substance


  • Kinetic store (due to their random motion / vibration)
  • Potential store (due to their position relative to each other)
• Together, the kinetic and potential stores form the total energy that makes up the internal energy of the system
• Molecules in a substance have kinetic energy since they are in motion and potential energy from their position relative to each other
• Heating


  Changes a substance's internal energy by increasing the kinetic energy of its particles
• Temperature


  Related to the average kinetic energy of the molecules
• Higher temperature


  Higher kinetic energy of the molecules and vice versa
• Increase in kinetic energy (and therefore internal energy)


  Can cause the temperature of the system to increase or produce a change of state (solid to liquid or liquid to gas)
• As the container is heated up


  The gas molecules move faster with higher kinetic energy and therefore higher internal energy
• Change of state


  When a substance reaches a certain temperature, energy will stop being transferred to the kinetic store of the molecules and will be transferred to their potential store instead
• This energy goes into overcoming the intermolecular forces of attraction between the molecules, causing them to move further apart from one another leading to a change of state
• When a substance changes its state, the potential energy of the molecules increases, allowing them to overcome the intermolecular forces of attraction, and the kinetic energy remains the same, meaning that the temperature will remain the same, even though the substance is still being heated