• “How hot or cold something is”

• Measures avg. K.E. of the particles in the object.

• Tool: thermometer – meas. in degrees.

• Scales~ Celsius (°C) 0° - 100°~ Fahrenheit (°F) 32° - 212°~ Kelvin (K) 273 K – 373 K

0 K – Absolute zero

TemperatureTemperature

Temperature ScalesTemperature Scales

• Grand total KE & PE inside a substance.

• Depends on temp & amount of substance.

• Which beaker has more internal energy? Why?

Internal EnergyInternal Energy

• Amount of internal energy required to change temp.

• A substance does not contain heat – it contains internal energy.

HeatHeat

• Thermal Contact – objects in contact or mixed. Heat flows from higher temp. substance to low temp. substance.

• Thermal Equilibrium – thermal contacts reach same temp. – no heat flow.– Qlost = Qgained

– There is no net change in energy! Energy is conserved!

HeatHeat

• The internal energy changes when heat flows into or out of objects.

• Q = mc∆t– Q = heat transferred (calories or joules)

– m = mass (g)

– C = specific heat (cal/g-°C) or (J/g-°C)

– ∆t = change in temp. (°C)

Changes in HeatChanges in Heat

• Ability of a sub. to store internal energy.

• The amount of heat needed to raise the temp. of 1 g of the material 1 °C.

• Units: cal/g-°C.

Specific Heat of Materials

Substance Specific Heat (cal/g-°C)

Water 1.00

Wood .42

Aluminum .22

Glass .16

Iron .11

Copper .09

Silver .06

Specific Heat CapacitySpecific Heat Capacity

or

J/g-°C

• calorie - the amount of heat needed to raise the temperature of 1 g water 1 °C.

• Kilocalorie = Calorie (food unit).– 1 Kcal = 1000 calories

• Joule 4.186 J = 1 calorie.

Units of HeatUnits of Heat

How much energy would it take for 1 kg of aluminum to change from 22 °C to 32 °C?

Q = mc∆t

Q = 1000 g · .216 cal/g-C · 10 °C

Q = 2,160 calories

Calculate Heat TransferredCalculate Heat Transferred

Let’s compute how much energy it takes to make a cup of coffee or tea. Eight ounces of water has a mass of 0.22 kg. How much heat must be transferred to water to raise its temperature from 20 °C to 100 °C?

Q = mc∆t

Q = 220 g · 1 cal/g-C · 80 °C

Q = 17,600 calories

Calculate Heat TransferredCalculate Heat Transferred

A 50 g piece of metal immersed in boiling water is placed in 100 g of water at 20 °C. The final temperature of metal and water is 28 °C. What is the specific heat of the metal? What is the metal?

QL = QG

mc∆t = mc∆t

Methods of MixturesMethods of Mixtures

(50g)(c)(72 °C) = (100 g)(1.0cal/g ·°C)(8 °C)

c = .22 cal/g ·°C aluminum

A 50.0 g block of iron at 80 C is dropped into a cup of 200 g of water at 22 C. The block cools to 40 C. What would be the temperature change of the water?

QL = QG

mc∆t = mc∆t

Methods of MixturesMethods of Mixtures

(50 g)( .11 cal/g·°C)(40°C)=(200g)( 1cal/g°C)(∆T)

∆T = 1.1 °C 22 °C + 1.1 °C = 23.1 °C is Tf

Jerry grabs a hot 350.0 g brass spoon from his bowl of soup, originally at a temperature of 95.0 C. To avoid burning his fingers he drops the spoon into a sink of 1,250 g water at 18.0 C. One second later, the spoon has cooled to a temperature of 75.0 C. Calculate the temperature of the water at this time.

QL = QG

mc∆t = mc∆t

Methods of MixturesMethods of Mixtures

(350 g) ( .09 cal/g·°C) (20°C) = (1250g) ( 1cal/g°C) (∆T) ∆T = .504 °C

18 °C + .504 °C = 18.504 °C is Tf

Mechanical EnergyMechanical Energy

• Relates to motion

Potential Energy = mgd

Kinetic Energy = ½mv2

Work = F x d

W = PE = KE Unit: Joule (J)

Thermal EnergyThermal Energy

• Relates to motion of molecules

Q = mc∆t

Unit: calorie or Joules

Conservation of EnergyConservation of Energy

• Energy can’t be created or destroyed, but can change forms, including between thermal and mechanical.

Elost = Egain

Qlost = Qgain

KE = Qgain

PE = Qgain

W = Qgain

Mechanical Equivalent of Heat

Mechanical Equivalent of Heat

• Relationship of mechanical energy to thermal energy.

W = PE = KE = Q

1 calorie = 4.184 J

A 5 kg concrete block falls 10 m to the ground. If all of the block’s energy is converted into heat that is absorbed by the block only, it’s temperature is raised _____?

PE = Q

mgd = mc∆t

Mechanical – Thermal Energy

Mechanical – Thermal Energy

5 kg · 9.8 m/s2 · 10 m = 5 kg · 670 J/kg-°C · ∆t

∆t = 0.15 °C

• Expansion of a substance due to heat.

Thermal ExpansionThermal Expansion

• ↑heat energy - ↑kinetic energy - ↑motion.• Gas/Liquid/Solid

– ↑temperature – expand– ↓temperature – contract

Phase ExpansionPhase Expansion

• As the temp. decreases from 4°C to 0°C, water expands - ice.– Its density

decreases.

• The maximum density of water (1.0 g/mL) occurs at 4°C.

Thermal Exp. of WaterThermal Exp. of Water

• Thermometer

• Sidewalk joints

• Building materials

• Thermostat – bimetallic strip

• Consequences??

Uses of Thermal Exp.Uses of Thermal Exp.

• Different materials expand at different amounts with the same temperature rise.

• Thermal Coefficients for Length & Volume.

– Solids (length) L = LO x x T

Expansion RatesExpansion Rates

L = change in length L0 = original length

= coefficient of linear expansion

T = change in temperature

Linear Expansion Coefficients

Linear Expansion Coefficients

Material Coefficient ( C –1 )

Aluminum 23 x 10-6

Brass 19 x 10-6

Copper 16 x 10-6

Glass 3.2 x 10-6

Gold 14 x 10-6

Iron (Soft) 12 x 10-6

Lead 29 x 10-6

Quartz .40 x 10-6

Steel 11 x 10-6

Expansion RatesExpansion Rates

•The Eiffel Tower, constructed in 1889 by Alexandre Eiffel, is an impressive latticework structure made of steel. If the tower is 301 m high on a 22 oC day, how much does its height decrease when the temperature cools to 0.0 oC?L = LO x x T

= 301 m • 10.5 x10-6 • 22 °C

= .070 m