THERMAL

• What does the internal energy of a substance include?

  Kinetic and potential energy of particles
• What is kinetic energy in molecules due to?

  The speed of the molecules
• What causes potential energy in molecules?

  Intermolecular forces and particle separation
• How is internal energy defined?

  Sum of kinetic and potential energies
• What does the symbol U represent?

  Internal energy of a substance
• What are the units of internal energy?

  Joules (J)
• How does temperature affect internal energy?

  Higher temperature increases kinetic energy
• Which phase of matter has the highest internal energy?

  Gases
• How can the internal energy of a system increase?

  By doing work or adding thermal energy
• How can the internal energy of a system decrease?

  Losing thermal energy or doing work
• What is the first law of thermodynamics about?

  Conservation of energy in a system
• When is internal energy increased according to the first law?

  When energy is transferred by heating or work
• What happens when a gas expands?

  Work is done by the gas on surroundings
• What occurs when a gas is compressed?

  Work is done on the gas by surroundings
• What happens to internal energy when a gas expands?

  Internal energy decreases
• What happens to internal energy when a gas is compressed?

  Internal energy increases
• What is specific heat capacity?

  Energy needed to raise 1 kg by 1 °C
• What is the symbol for specific heat capacity?


  c
• What are the units of specific heat capacity?

  J kg–1 K–1 or J kg–1 °C–1
• How does mass affect specific heat capacity?

  Heavier materials need more energy
• What is the formula for calculating thermal energy change?

  ΔQ = mcΔθ
• What does ΔQ represent in the formula?

  Change in thermal energy (J)
• What does m represent in the formula?

  Mass of the substance (kg)
• What does c represent in the formula?

  Specific heat capacity (J kg–1 K–1)
• What does Δθ represent in the formula?

  Change in temperature (K or °C)
• How does specific heat capacity affect heating and cooling?

  Low capacity heats and cools quickly
• Why do good electrical conductors also conduct heat well?

  Due to their low specific heat capacity
• What is latent heat?

  Energy required to change state without temperature change
• What are the two types of latent heat?

  Fusion and vaporisation
• What happens during a change of state?

  No temperature change occurs
• What is the specific latent heat of fusion?

  Energy to convert 1 kg solid to liquid
• What is the specific latent heat of vaporisation?

  Energy to convert 1 kg liquid to gas
• What is the formula for calculating latent heat?

  Q = mL
• Why does vaporisation require more energy than fusion?

  More energy needed to separate molecules completely
• What is thermal equilibrium?

  Same final temperature for materials in a system
• What happens when ice is added to a warm drink?

  Energy is transferred to the ice
• How is energy transfer indicated in calculations?

  With a negative sign for energy released
• What is the equation for energy transfer in mixtures?

  ΔQ_colder = -ΔQ_warmer
• What must be included in calculations if a material changes phase?

  Energy needed for the phase change
• What happens to kinetic energy during a phase change?

  No change occurs in kinetic energy