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Thermal EnergyChapter 6
Temperature
Matter is in constant random motion, and hot particles move faster than cold ones because hot particles have more kinetic energy
Temperature is the measure of the average kinetic energy of the particles of an object
Temperature is often measured in Celsius or Fahrenheit
Heat
Heat is thermal energy that flows from something from higher temperature to something at a lower temperature
Heat is a type of energy, so it is measured in Joules
When ice melts, the thermal energy from the warmer air transfers to the colder ice, making it melt
Specific Heat
The amount of heat needed to raise the temperature of 1 kg of a substance’s temperature 1 degree Celsius
The higher the specific heat, the more energy is needed to change the temperature of the substance
Water has a very high specific heat Metal and sand have a very low
specific heat
Water as a Coolant
Water has a very high specific heat, meaning it takes a lot of energy to break the bonds between the molecules and allow the temperature to rise
Because of this, water is used as a coolant
Think of a swimming pool vs the concrete around the pool
Calculating Heat Energy
Q= Heat Energy in Joules
ΔT= Change in Temp in degrees C
M= mass in kg C= specific
heat (constant)
Q
M C ΔT
Specific Heat Constants
Substance Specific Heat (J/kg·Co)
aluminum 900copper 387
ice 2,060lead 128silver 235
ethyl alcohol 2450mercury 138
water 4186air 1005
oxygen 912steam 2009
Transferring Thermal Energy
Conduction- heat transfer by touching Example: A metal spoon in hot coffee Sitting in a chair and the chair gets
warm The best heat conductors are metals,
silver, copper and aluminum are the best conductors of heat
Convection
Transfer of thermal energy in a fluid by the movement of fluids from a warmer place
Example: Heating up water in a bathtub by adding more hot water
Lava Lamp Example: Weather
patterns
Radiation
Earth gets heat from the sun, heat can only travel from the sun to the Earth by radiation, because conduction and convection both require matter
Radiation is the transfer of energy by electromagnetic rays
Often called radiant energy
The Electromagnetic Spectrum
Controlling Heat Flow
Putting on a coat or an oven mitt are both examples of trying to control the flow of heat
Many animals have adaptations that help them control the flow of heat
Penguins have a layer of blubber and thick, closely spaced feathers
Reptiles have scaly skin that helps to reflect sunlight
Insulators
A material in which heat flows slowly Gases are usually better insulators
than solids are liquids Buildings are insulated to keep warm
air in the building during the winter and cool air in the summer
Fleece jackets trap warm air pockets close to your body