Energy Conservation and Energy Conservation and TransferTransfer

Chm 2.1.1Chm 2.1.1

States of MatterStates of Matter

Solid KMTSolid KMT– particles packed tightly together particles packed tightly together – high attractionhigh attraction– Lowest energy of all statesLowest energy of all states– Volume: definiteVolume: definite– Shape: definiteShape: definite– Density: High (incompressible)Density: High (incompressible)– Types: Crystalline and AmorphousTypes: Crystalline and Amorphous

States of MatterStates of Matter

Liquid KMTLiquid KMT– particles are particles are ““fluidfluid””, , – less attractionless attraction– Higher energy than in solidsHigher energy than in solids– Volume: definiteVolume: definite– Shape: not definiteShape: not definite– Density: relatively highDensity: relatively high

States of MatterStates of Matter

Gases KMTGases KMT– particles are spread apartparticles are spread apart– very low or no attractionvery low or no attraction– Highest energyHighest energy– Volume and Shape not definiteVolume and Shape not definite– Density: very lowDensity: very low– able to be compressedable to be compressed

States of MatterStates of Matter

Phase Changes of MatterPhase Changes of Matter

EndothermicEndothermic– Melting (liquefying)Melting (liquefying)– Boiling Boiling – Vaporization (Evaporation)Vaporization (Evaporation)– SublimationSublimation

ExothermicExothermic– Freezing (solidifying)Freezing (solidifying)– CondensingCondensing– DepositionDeposition

TemperatureTemperature

Measures Measures ““speedspeed”” or Kinetic Energy of or Kinetic Energy of particles (T)particles (T)

Measured in Measured in ºC or Kelvin (K)ºC or Kelvin (K)

K = ºC + 273K = ºC + 273

Heat measures energy absorbed or Heat measures energy absorbed or released (q)released (q)

Measured in joules (J) or kilojoules (kJ)Measured in joules (J) or kilojoules (kJ)

Equilibrium in Changes of StateEquilibrium in Changes of State

Equilibrium: a dynamic condition in which Equilibrium: a dynamic condition in which two opposing changes occur at equal two opposing changes occur at equal rates, at the same time in a closed systemrates, at the same time in a closed system

EquilibriumEquilibrium

VaporizationVaporization liquid + heat energy liquid + heat energy vapor vapor

CondensationCondensationvapor vapor liquid + heat energy liquid + heat energy

At EquilibriumAt EquilibriumLiquid + Heat Energy Liquid + Heat Energy ↔ Vapor↔ Vapor

Vapor PressureVapor Pressure

Vapor Pressure = vapor molecules at Vapor Pressure = vapor molecules at equilibrium exert pressureequilibrium exert pressure

Effects of Temperature of Vapor PressureEffects of Temperature of Vapor Pressure– Increase Temperature = increases VPIncrease Temperature = increases VP– Decrease Temperature = decrease VPDecrease Temperature = decrease VP– Boiling = when VP of liquid is = to the Boiling = when VP of liquid is = to the

atmospheric pressureatmospheric pressure

Phase Diagram for HPhase Diagram for H22OO

Phase Diagram for COPhase Diagram for CO22

Heating CurvesHeating Curves

Heat CalculationsHeat Calculations

Specific heat: Specific heat: – The amount of energy needed to raise 1g of a The amount of energy needed to raise 1g of a

substance 1substance 1°C or 1K°C or 1K– Cp = J/g°C or J/gKCp = J/g°C or J/gK– Measured under conditions of constant Measured under conditions of constant

pressurepressure– All substances have their own specific heatAll substances have their own specific heat– Cp = q/mCp = q/mΔΔTT

Calculating HeatCalculating Heat

Calculating Heat from CpCalculating Heat from Cp– q = mCpq = mCpΔΔTT

Ex: Calculate the amount of heat absorbed by a Ex: Calculate the amount of heat absorbed by a 6.0g sample of aluminum when the 6.0g sample of aluminum when the temperature is increased from 500°C to temperature is increased from 500°C to 550°C. 550°C.

The heating curve above gives data for water The heating curve above gives data for water when it is cooled. How much heat energy is when it is cooled. How much heat energy is released from 4.0g of water when it is cooled released from 4.0g of water when it is cooled from 100from 100° to 0°° to 0°

Heat of FusionHeat of Fusion

The amount of energy required/released The amount of energy required/released when melting/freezing 1g of water at 0when melting/freezing 1g of water at 0°C°C

Hf = 334 J/g Hf = 334 J/g

q = mHfq = mHf

Ex: how much energy will be absorbed by a Ex: how much energy will be absorbed by a 3.0g ice cube at 0°C?3.0g ice cube at 0°C?

Heat of VaporizationHeat of Vaporization

The amount of energy absorbed or The amount of energy absorbed or released when vaporizing/condensing 1g released when vaporizing/condensing 1g of water at 100of water at 100°C°C

Hv = 2,260 J/gHv = 2,260 J/g

q = mHvq = mHv

Example: How much energy is absorbed Example: How much energy is absorbed when 9.36 g of water is vaporized?when 9.36 g of water is vaporized?

Law of Conservation of EnergyLaw of Conservation of Energy

In a closed systemIn a closed system– Energy is cannot be created or destroyed only Energy is cannot be created or destroyed only

transferred. transferred. – heat lost in a system is gained by the heat lost in a system is gained by the

surroundingssurroundings– Heat gained in a system is lost by the Heat gained in a system is lost by the

surroundingssurroundings– q lost = q gainedq lost = q gained

An ice cube while melting gained 25 J of An ice cube while melting gained 25 J of energy. How much energy was lost by its energy. How much energy was lost by its surroundings?surroundings?

A hot piece of metal is put into a cup of A hot piece of metal is put into a cup of water. What will happen to the metal? water. What will happen to the metal? What will happen to the water?What will happen to the water?

Copper was heated Copper was heated and placed in a cup of and placed in a cup of water at room temperature (25°C). The water at room temperature (25°C). The waterwater’’s temperature rose 30°C. How much s temperature rose 30°C. How much energy did the copper loose?energy did the copper loose?