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Relationship between
Types of Energy Changes during Heating or Cooling
Particles in all states of matter contain energy in two main forms:
When particles gain or lose heat, they gain or lose thermal energy
As all particles are in constant motion, they contain kinetic energy
Changes in kinetic energy of the particles is dependent on changes in temperature
During changes in state, the temperature remains constant at the melting and boiling point of the substance
There is no changes in kinetic energy during changes in state
How does energy changes when there are changes in temperature?
During heating:
Particles in a substance gains/absorbs thermal energy from the surroundings
The thermal energy in particles is converted to kinetic energy, which causes the particles to move faster
An increase in kinetic energy results in an increase in temperature
During cooling:
Kinetic energy is converted back to thermal energy which is released/transferred to the surroundings
A decrease in kinetic energy causes the particles to move slower
A decrease in kinetic energy results in a decrease in temperature
How does energy changes when there are changes in state?
When substances changes state (e.g., melting, boiling, freezing, condensation), the temperature remains constant (especially in pure substances).
Instead of being converted to kinetic energy, the thermal energy is used to overcome the forces of attraction between particles
There is no change in average kinetic energy of the particles during state change
During heating (melting or boiling):
Particles absorb thermal energy from the surroundings to overcome forces of attraction between the particles (in solid/liquid state)
During cooling (freezing or condensation):
Particles lose thermal energy to the surroundings.
Particles with less energy are drawn closer together by the forces of attraction between them.
Resources:
Phet Simulation: States of Matter (Link)
Simulation: Ice, Water and Water Vapour (Link)
Video: Discussion about Thermal Energy, Kinetic Energy and Changes in Temperature (Video 1)(Video 2)
Video: Experiments demonstrating how kinetic energy can be converted to thermal energy (Link)
Video: Discussion about Thermal Energy and Changes in State (Video 1)(Video 2)(Video 3)
Video: Demonstration showing State Changes using Liquid Nitrogen (Link)
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