Internal energy

• What is internal energy?

  The total energy stored in a system due to the kinetic and potential energy of its particles.
• What are the two components of internal energy?

  1. Kinetic energy - due to particle motion.

  2. Potential energy - due to forces between particles.
• How does heating affect the internal energy of a substance?

  Heating increases internal energy by increasing either the kinetic energy (raising temperature) or potential energy (changing state).
• What happens to internal energy during a change of state?

  Energy is used to break or form bonds, changing the potential energy, while the temperature remains constant.
• What is specific heat capacity?

  The energy required to raise the temperature of 1 kg of a substance by 1°C.
• What is specific latent heat?

  The energy required to change the state of 1 kg of a substance without changing its temperature.
• What are the two types of specific latent heat?

  • Latent heat of fusion (solid -> liquid).
  • Latent heat of vaporisation (liquid -> gas).
• Why does temperature remain constant during melting or boiling?

  Energy is used to break bonds rather than increase kinetic energy, so temperature stays the same.
• Why do gases have higher internal energy than solids?

  Gases have faster-moving particles with more kinetic energy and weaker intermolecular forces.
• How does increasing temperature affect internal energy?

  Higher temperature means more kinetic energy, increasing the total internal energy of the system.
• Why does a swimming pool contain more internal energy than a cup of tea, even if the tea is hotter?

  The swimming pool has a much greater mass, so its total internal energy is higher, even though the tea has a higher temperature.