Thermal Energy

Temperature Measures the “hotness” (higher temperatures) or “coldness” (lower temperatures) Gives very little information on the energy that the material contains.

Temperature  Heat Some equate temperature to heat Temperature and Heat are not the same

Temperature All matter is made up of tiny particles These tiny particles are constantly moving

All moving things have kinetic energy The faster the particles move the more KE The temperature is a measure of the average Kinetic Energy

Thermal Energy Place a ice-cold spoon on ice cream. What happens? Place a hot spoon on ice cream. What happens?

Place two hot spoons on ice cream. How is it different? Pour hot water on the ice cream. How is this different from the spoon?

Thermal Energy Thermal energy is the total amount of kinetic and potential energy of a material Kinetic energy determined by the speed of the moving particles

Potential energy determined by the distance between the particles

Thermal Energy & Temperature They are related As temperature increase so does the kinetic energy and the potential energy of the particles

Thermal Energy Depends upon temperature Mass of material Type of material

Heat The transfer of thermal energy

Heat Heat is the energy that flows from an object of higher temperature to an object with lower temperature Heat is measured in units of Joules

So… Does an ice cube in warm water cause the water to cool down Or does the warm water cause the ice cube to melt?

Specific Heat Why is the air around the swimming pool warmer than the water even if they have both been exposed to the sun the same amount of time?

Different materials need different amounts of heat to change the temperature the same amount. Copper pot –vs- water

Specific Heat is the amount of heat necessary to raise the temperature of one kilogram of a material one degree Celsius

Units (J/kg.Co) Specific heat of water very high Advantages? Disadvantages?

Measuring Specific Heat Cannot measure the amount of heat energy transferred Can only measure the resultant change in thermal energy

Q = mcDT m-mass in grams or kilograms Q- thermal energy in Joules c-specific heat in J/kg.Co or J/g.Co DT-change in temperature in Co

Change in Length When temperature is increased objects expand Sidewalks, siding on houses, railroad tracks, bridges, etc…

Dl=laDT Dl-change in length l-original length a-coefficient of linear expansion DT-change in temperature

Change in Volume Liquids expand 100 times more than solids DV=VbDT

DV-change in volume V-original volume b-coefficient of volume expansion DT-change in temperature