Thermal Physics
Internal energy
Boiling and condensation
Evaporation
Melting and solidification
-Unit in joule
-The particles in a substance are in continuous motion and attractive forces exist between these such as intermolecular bonds
Internal potential energy
-Due to stretching of bonds as particles move
-Potential energy between the particles depends on forces between them and how far apart they are
Internal kinetic energy
-Due to motion of particles
-Directly related to temperature- the higher the temperature, the more vigorous the motion of particles
Melting
-Temperature does not change during melting
-Definite temperature for pure substances
-Energy is absorbed to break down forces of attraction between particles and only internal KE is changed.
Solidification
-Temperature does not change during freezing
-Definite temperature for pure substances
-Energy is released to form strong forces of attraction and only internal KE is changed.
Boiling
-No change in temperature
-Definite temp for pure substances
-Energy is absorbed to break down forces of attraction between particles and only internal KE is changed.
Condensation
-No change in temp
-Definite temp for pure substances
-Energy is released to form strong forces of attraction and only internal KE is changed.
Similar to boiling but has differences
It causes cooling
Evaporation:
-Occurs at any temperature
-Relatively slow
-Takes place only at the surface of the liquid
-No bubbles are formed
-Temp may change
-External thermal energy not needed
Boiling:
-Occurs at a particular temp
-Relatively fast -Takes place throughout the liquid
-Bubbles are formed
-Temp remains constant
-External thermal energy needed
eg. perfume, swimming and coming out afterwards and fridge
Transfer of thermal energy
Model of matter
Solid
Liquid
Gas
Randomly arranged and far apart
Move rapidly in all directions
Arranged in an orderly manner
Vibrate about fixed positions
Randomly arranged and further apart
Slide past one another
Conduction
Convection
Radiation
Real-life examples
Transfer of thermal energy without any flow of medium
Travel from high temp to low
Only in solids and is faster in metals due to free electron diffusion
Not efficient in liquids and gases
Transfer of thermal energy by convection in a fluid due to difference in density using convection currents
Only in liquids and gases
Transfer of thermal energy without a medium through EM waves
Affected by colour ( darker is better emitter), texture (rougher is better), surface temperature (higher is better), surface area (larger is better)
Conduction
Convection
Radiation
Good- cooking utensils, soldering iron tips
Bad/Poor- handles of appliances, table mats, clothing, windows
Electric kettles, hot water systems, air-con
Green houses, vacuum flasks