CH 10 HEATpgs. 357 - 386

TEMPERATUREAdding or removing energy

usually changes temperatureTemperature is proportional to the

kinetic energy of atoms and molecules

TEMPERATURETemperature is meaningful only

when it is stableThermal Equilibrium – the state

when two objects in physical contact have identical temperatures

Matter expands as temperature increases (thermal expansion)

MEASURING TEMPERATUREThermometers

Most make use of a change in the volume of a gas or liquid

Most are thin glass tubes containing mercury, colored alcohol, or colored mineral spirits

MEASURING TEMPERATURECalibrating thermometers

requires fixed temperaturesIce point of water – thermometer in

equilibrium with a mixture of ice and water at 1 atm

Steam point of water – thermometer in equilibrium with a mixture of steam and water at 1 atm

TEMPERATURE CONVERSION Temperature in Fahrenheit (TF )

Units are °F Temperature in Celsius (TC)

Units are °C

TEMPERATURE CONVERSION Temperature in Celsius (TC)

Units are °C Temperature in Kelvin (T)

Units are K

HEAT AND ENERGYHeat – the energy transferred

between objects because of a difference in their temperatures

Always moves from the object with the higher temperature to the object with the lower temperature

HEAT AND ENERGY

HEAT AND ENERGYThe transfer of energy as heat

alters an object’s temperatureEnergy transfer depends on

the difference of temperature of the two objects

HEAT AND ENERGYGreater temperature difference =

greater amount of energy transferred

At thermal equilibrium, the net energy exchanged is zero

HEAT (Q)Heat (Q) has units of energy

INTERNAL ENERGY (U)The energy of a substance due to

atomic motionUnits are Joules (J)

INTERNAL ENERGY (U)Internal energy can be changed

through work (friction)The energy required to overcome

friction is transformed into internal energy

Internal energy can also be changed by deforming a solid’s structure Stretching a rubber band or bending

metal

CONSERVATION OF ENERGY

CONSERVATION OF ENERGY

½ mvi2 + mghi = ½ mvf

2 + mghf + ΔU

A device used to demonstrate energy conservation is shown. If a total mass of 11.5 kg falls 1.3 m and all of the mechanical energy is converted to internal energy, by how much will the internal energy of the water increase? (Assume no energy is transferred to or from the surroundings.)