CH 10 HEATpgs. 357 - 386

PHASE CHANGECalorimetry only works when

substances do not change phase

Phase change – the physical change of a substance from one state to another at constant pressure

PHASE CHANGEPhase changes involve potential

energy between particlesThe farther apart the particles are,

the more potential energy is present

PHASE CHANGE Bonds can be broken by particles

moving far away from each other

Bonds can be formed by particles moving closer together

Decreasing the Potential Energy by moving from high potential energy (large separation) to low potential energy (small separation) will Increase the Kinetic Energy

HEAT OF FUSION (LF)

Units of J/kgEnergy required to melt a substance

goes into rearranging the moleculesHeat of Fusion – the energy per unit

of mass transferred to change a substance from liquid to solid or solid to liquid at constant temperature and pressure

HEAT OF FUSION (LF)

HEAT OF VAPORIZATION (LV)

Units of J/kgEnergy required to vaporize a

substance mostly goes into separating the molecules

Heat of Vaporization – the energy per unit of mass transferred to change a substance from liquid to vapor or vapor to liquid at constant temperature and pressure

HEAT OF VAPORIZATION (LV)

LATENT HEAT (L)More energy is required to

vaporize a mass of substance than to melt it

Heat of Vaporization is greater than Heat of fusion

Latent Heat – energy per unit mass that is transferred during a phase change of a substance (both heat of vaporization and heat of fusion)

LATENT HEAT (L)Units of J/kg

CONTROLLING HEATThermal Conduction – energy is

transferred as heat between objects through contact

Thermal Conductors – substances that rapidly transfer heat

Thermal Insulators – substances that slowly transfer heat

CONTROLLING HEATConvection – transfer of heat

through the displacement of cold matter by hot matterInvolves pressure differences,

conduction and buoyancyElectromagnetic Radiation –

reducing internal energy by radiating electromagnetic radiationDoes NOT involve matter

CLOTHING AND CLIMATE

Cold Climates Without proper insulation, the body

will try to reach equilibrium with its surroundings

Hypothermia – lower pulse, blood pressure, respiration

Insulating materials retain energy for cold climates

CLOTHING AND CLIMATE

Hot Climates Evaporation aids energy transfer in hot

climates Heat exhaustion or heat stroke will

result if the body’s temperature becomes too high

How much energy is removed when 10.0 g of water is cooled from steam at 133.0°C to liquid at 53.0°C?

How much energy is removed when 10.0 g of water is cooled from steam at 133.0°C to liquid at 53.0°C?