Thermal energy

Atoms and molecules in matter are in constant, random movement.

Temperature of an object = the measure of the average kinetic energy of the
particles in that object. Thermometers are used to measure. Celsius and Kelvin
are scientific units for this measurement.

Collisions between particles transfer the energy from high energy to
low energy particles

Particles have attractive forces to each other = gravitational potential
energy

Thermal energy = the sum of the kinetic and potential energy of all
the particles in an object

An iceberg has more thermal energy than a hot cup of coffee

Increase in temperature means an increase in the average kinetic energy of
an object which then means an increase in thermal energy

If temperature does not change, thermal energy in object increases
if mass increases (more particles)
Heat = thermal energy that flows from something at a higher
temperature to something at a lower temperature. Measured in joules.
As substances absorb heat, its temperature changes.
Specific heat = the amount that is needed to raise the temperature
of 1 kg of some material by 10C.
Water has a high specific heat because water molecules form strong
bonds with each other; Water is therefore very useful as a coolant.
Change in thermal energy = mass X change in temperature X specific
heat of substance
Q = m(Tf - Ti)Cp
To measure specific heat; use a calorimeter
the heated substance transfers heat to a known quantity/mass of water; the
energy absorbed by the water can be calculated by measuring the
water's temperature change.
Three methods of thermal energy transfer: (know definitions)
1. Radiation
2. Conduction
3. Convection
Types of currents on Earth
i. Atmospheric currents
ii. Plate tectonics
iii. Ocean breezes
Understand difference between conductors and insulators
…between thermal expansion and contraction
Heating Systems
All require energy
Heat transfer is slow - disadvantage
Types:
1. Forced air systems - heating air by
convection using fans
2. radiator system - hot water/steam
heats air by conduction then warms
airs through convection
3. electric heating systems - heat coils by conduction then heat air by
convection
Solar heating
Passive - absorption of heat by materials in room
Active - solar collectors/solar panels
Heat engines - convert heat into work
Internal combustion engine - only 25-30% heat changed to work
friction of parts transferred into heat
Please know the 4 steps in a four stroke engine cycle – see figure in textbook
Heat movers - uses work to move heat from cooler temperature to warmer temperature
Ex) refrigerator - compressors use mechanical energy to move thermal energy in
the reverse of law of conservation of energy
Liquid coolant -> cold gas -> absorbs thermal energy -> compressor -> increases
temperature of gas -> thermal energy leaves gas into room -> gas changes to
liquid -> cycle begins again
Ex) air conditioners - warm air forced over tubes with coolant; air is cooled and
forced back into room
Heat pump - 2-way heat movers
in warm weather, it works like an air conditioner
in cool weather, reverse
coolant is cooled and pumped outside, absorbs heat from outside air,
compressed and into home, releasing heat
Human coolant - sweat evaporates carrying heat away from body cooling you