14. Thermal Properties of Matter Flashcards
Internal Energy
Definition
The internal energy of a substance is the sum of the kinetic energy due to the random motion of the particles and potential energy due to forces of attraction between the particles
Internal kinetic energy - temperature
Internal potential energy - state
Heat capacity (C)
Definition
Heat capacity (C) is the amount of heat required to raise the temperature of a substance by 1K (or 1°C)
Unit: J K-1
Specific Heat Capacity (c)
Definition
Specific heat capacity (c) is the amount of heat required to raise the temperature of a unit mass of a substance by 1K (or 1°C).
Unit: J kg-1 K-1
Melting
Defintion
Melting is the change from the solid state to the liquid state when energy is transferred to the substance, without a change in temperature.
Solidification/Freezing
Definition
Soldification/Freezing is the change from the liquid state to the solid state when energy is transferred out of the substance, without a change in temperature.
Boiling
Definition
Boiling is the change from the liquid state to the gaseous state when energy is transferred to the substance without a change in temperature.
Condensation
Definition
Condensation is the change from the gaseous state to the liquid state when energy is transferred out of the substance without a change in temperature.
Latent Heat
Definition
Latent heat is the energy released or absorbed to change the state of a substance, at constant temperature.
2 types of latent heat:
Latent heat of fusion & Latent heat of vaporisation
Describe latent heat during melting in terms of behavior of particles
During melting, the energy absorbed is used to do work against the forces of attraction between the partlces.
The particles now have a wider range of movement, and the average distance between the particles increases.
This increases the internal potential energy of the substance, whereas the internal kinetic energy remains constant.
Describe latent heat during boiling in terms of behaviour of particles
During boiling, the energy absorbed is used to do work against the forces of attraction between the particles, so they can move much further apart,
as well as to do work against atmospheric pressure, in order to escape to the surroundings.
This increases the internal potential energy of the substance, whereas the internal kinetic energy remains constant.
Describe latent heat during freezing in terms of behaviour of particles
During freezing, the energy released to the surroundings causes the forces of attraction to reform around the particles.
The particles now are restricted to fixed positions, and the average distance between particles decreases.
This decreases the internal potential energy of the substance, whereas the internal kinetic energy remains constant.
Describe latent heat during condensation in terms of behaviour of particles
During condensation, the energy released to the surroundings causes the forces of attraction to reform around the particles.
The average distance between particles decreases.
This decreases the internal potential energy of the substance, whereas the internal kinetic energy remains constant.
Latent Heat of Fusion (Lf)
Definition
Latent heat of fusion is the amount of heat required/released to change a substance between the solid and liquid states, at constant temperature.
Unit: J
Specific Latent Heat of Fusion (lf)
Definition
Specific latent heat of fusion is the amount of heat required/released to change a unit mass of a substance between the solid and liquid states, at constant temperature.
Unit: J kg-1
Latent Heat of Vaporisation (Lv)
Definition
Latent heat of vaporisation is the amount of heat required/released to change a substance between the liquid and gaseous states, at constant temperature.
Unit: J