Internal Energy

• What is meant by internal energy?

  Energy stored in a system by particles
• What happens to particles in a solid?

  They vibrate but do not move
• How do particles in a liquid behave?

  They can move around each other
• What is the movement of particles in a gas?

  They move extremely rapidly
• What type of energy do all particles possess?

  Kinetic energy
• What additional type of energy do particles have besides kinetic energy?

  Potential energy
• What are intermolecular forces?

  Forces between particles that give potential energy
• What does internal energy include?

  Total kinetic and potential energy of particles
• Why is internal energy important during changes of state?

  It determines the state of the material
• What happens to internal energy when a solid is heated?

  It increases
• What is the process called when a solid turns into a liquid?

  Melting
• What happens when a liquid is heated further?

  It turns into a gas
• What is the process called when a liquid turns into a gas?

  Boiling
• What happens to internal energy when a gas is cooled?

  It decreases
• What is the process called when a gas turns back into a liquid?

  Condensation
• What happens when a liquid is cooled further?

  It turns into a solid
• What is the process called when a liquid turns into a solid?

  Freezing
• What is sublimation?

  Solid turning directly into a gas
• What is an example of sublimation?

  Carbon dioxide at room temperature
• What happens to mass during changes of state?

  Mass is always conserved
• What type of changes are changes of state?

  Physical changes
• What happens if you reverse a change of state?

  The material recovers its original properties
• What is evaporation?

  Liquid turning to gas at the surface
• Which particles turn into gas during evaporation?

  Only surface particles with enough energy