Chapter Twelve (the other half…)

TEMPERATURE & HEAT

SPECIFIC HEAT: The quantity of energy required to raise the temperature of 1 kg of a substance by 1° C.

Different for each substance

Cwater = 4186 J/Kg·°C

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Q = cmΔT

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c =Q

mΔT

SPECIFIC HEAT CAPACITY: TEMPERATURE CHANGE

CALORIMETRY: Procedure to measure energy transfer in the form of heat

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Qa = −Qb

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camaΔTa = −cbmbΔTb

Example ProblemA 115 g mass of lead at 100.0 degrees Celsius

is placed in a 220 g sample of water at 20.0 ºC . What is the final temperature reached by the two substances?

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cama (Taf −Tai) = −cbmb (Tbf −Tbi)

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4186(.22)(Tf −20) =−128(.115)(Tf −100)

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921Tf − 18400 = −14.7Tf + 1470€

camaΔTa = −cbmbΔTb

128 J/Kg °C

Energy and Temperature

SpecificHeat

SpecificHeat

SpecificHeat

LatentHeat

LatentHeat

LATENT HEAT: PHASE CHANGE

• Heat of vaporization– Liquid to gas

• Heat required to cause a PHASE CHANGE

• Heat of fusion

- Solid to Liquid

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Q=mLf

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Q = mLv

Energy and Temperature

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Q = cmΔT

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Q = mLf

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Q = cmΔT

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Q = mLv

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Q = cmΔT

BOAT FIRE PROBLEM…• How much energy is required to

elevate the temperature of a 1000 gallons of water from 60° F to 212° F and then to vaporize it to steam?

1 Gallon = 0.00379 m

Boat Problem

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Q = cmΔT

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Q = mLv

How much energy is required to elevate the temperature of a 1000 gallons of water from 60° F to 212° F and then to vaporize it to steam?1 Gallon = 0.00379 m