Kinetic Molecular Theory

•All matter is made of molecules

•These are always in motion

•Their motion is directly related to temperature.

•Demo

Heat Defined

•Heat is a form of energy

•It is caused by the motion of molecules

•Give credit to: Count Rumford (aka: Benjamin Thompson)

•Heat is a kinetic energy

Heat Transfer• Heat moves from hot to cold.

• It can do this through:

–Conduction

–Convection

–Radiation

Conduction

When there is direct contact between objects and heat is transferred.

Convection

When there is transfer of heat in fluids

The hot fluid rises, due to its lower density

Convection Cells

Radiation

When heat moves as an electromagnetic wave

Temperature Versus Heat

•Temp. is a measure of the average velocity of the molecules

•Heat is a form of energy caused by this motion

..the higher the temperature, the more energy something has

But…

… temperature is NOT a direct measure of the amount of heat

Measuring heat

• Heat is measured in calories

• A calorie is 4.19 joules• A calorie is how much heat is

needed to get one gram of water to go up one degree Celsius.

Think about this…

• You have a swimming pool that is 10º C

• You have a cup of hot cocoa

• Which has a higher temperature?

• Which has more heat?

Temperature Versus Heat

• Heat= total energy

•Temperature= average energy

Temperature Scales

• Fahrenheit• Celsius • Kelvin • link

Ab zero

Bases

Specific heat

• An indicator of how hard/easy it is to get a substance to go up or down in temperature

Specific Heat

• The amount of heat needed to raise 1 gram of a substance by 1° C

• Unit= cal / g° C

• Water is easy, it is:1 cal / g° C

Calorimeter

• A device to measure heat

• All you do is measure water and see how much it goes up in temperature

Calorimeter

•The heat lost by an object is gained by the water in the calorimeter

•Equation for Heat lost or gained: =Mass x ΔT x specific heat