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