HeatThe energy transfer from one object to another because of a temperature difference between themMatter doesnt contain heat..Contains energy..Heat is energy in transit

Heat Thermal Contact....When heat flows from one object to another that it contactsEnergy that flows from areas that are higher in temp to areas that are lower in tempThere is NO such thing as cold

Measurement of HeatTo quantify heat, we must specify the mass and the kind of substance affectedcalorie.The amount of heat required to raise the temperature of 1 gram of water by 1oCCalorie.1000 calories food

Specific Heat (c)The amount of heat required to raise the temp of 1mass unit of a substance by 1 temp. unit.Thermal inertia signifies the resistance of a substance to change in temp.

Computing thermal expansionQ = mCTQ = heat gained or lost (J)m = mass (kg)T = change in temp (K)C = specific heat (J/kg K)

CalorimeterDevice used to measure changes in thermal energyit is a closed system to measure energy transfer

Heat of Fusion HfAmount of energy needed to melt one kg of a substanceice= 3.34 x 105 J/kgice= 80 cal

Melting PointTemp at which a substance changes from a solid to a liquidsame temp. as freezing point

Heat of Vaporization HvAmount of energy needed to vaporize a kg of liquidwater = 2.26 x 106 J/kgwater= 540 cal

Boiling PointTemp at which a substance changes from a liquid to a gasSame as temp for condensation to occur

Q=mHf or Q=mHvQ.heat required to melt a solid or vaporize a liquidm.mass

Thermal EnergyThe total energy of particles in a material. KE and PE

Thermal Energy TransferOccurs in 3 waysCONDUCTIONCONVECTIONRADIATION

ConductionTransfer of energy from molecule to moleculeMost common in solidsKE is transferred when particles collideMUST have direct contact

ConductorsMaterials that conduct heat wellMetals.Silver

InsulatorsA material that is a poor conductorDelays the transfer of heatExamples wood, wool, straw, paperPoor conductor is a good insulator

ConvectionMovement of all fluids (gas or liquid) Caused by substances having diff. Densities at diff. temps.Movement occurs in currents Example.water, air

RadiationThermal energy transferred through space in the form of electromagnetic waves.Examples .Solar energy,

ExampleWhat does this mean?Convert to grams because we know what one cal does to one gram.

Specific HeatHeat Capacity = amount of heat required to raise T by 1oCNot very useful because it is not a property of the materialSpecific Heat = Heat Capacity per unit massIntrinsic property of the material

CalorimetryConservation of EnergyAssume that no energy is lost to the surroundingsHeat Gained = Heat Lost

CalorimetryAssume that we drop a lump of gold (m = 20 g) at 100oC into 50 g of water at 20oC. What is the final equilibrium temperature?Heat lost = mgcg(Tg Te)Heat gained = mwcw(Te Tw)note that both are positiveequate and solve for Te

CalorimetryDo we need to use Kelvin temperatures?

CalorimetryLets check to see if this is correct.It checks! The small difference is due to roundoff.

Latent HeatIt requires heat to change the phase of a substance.Latent Heat is an intrinsic propertyper unit massHeat of fusion of water = 80 cal/gHeat of vaporization of water = 540 cal/gQ = mL

Latent HeatHow much heat released in converting 1 g of steam at 120oC to ice at 30oC?

Cool steam, condense, cool water

Freeze and cool ice

ExampleA glass contains 120 g of ice at 0oC. What is the equilibrium temperature if you add 400 g of water at 20oC?Heat gained = heat lost

ExampleWhat ?!?Check for mistakes.There are no mistakes.We made the assumption that all of the ice melted. Actually only 100 g melted!

**VD Encyc 15 #12 - Drinking BirdVD Encyc 15 #13 - Freezing by BoilingVD Encyc 15 #14 - CryophorousVD Encyc 15 #16 - Regelation *****