Transcript 10.2 Thermal Energy Transfer p. 375

The Earth’s surface, especially water, has a
HUGE influence on our climate and weather.
70% of Earth’s surface is covered with
water
 Water plays a major role in the
absorption and distribution of thermal
energy, influencing both weather and
climate: the great
moderator

The amount of heat (J) required to
raise the temperature of 1 g of a
substance by 1o C


It takes a lot of solar radiation to heat
water, so water is a heat sink.
It absorbs a great deal of solar radiation,
keeping the region cooler during the day,
and it slowly reradiates the heat at night
SUBSTANCE
c (J /g oC)
Pure water
4.19
Steam
2.02
Ice
2.00
Sea water
3.89
Moist air
1.15
Dry air
1.00
Pg. 375
Q = mcΔT
c
ΔT
m
Q
= specific heat capacity
= change in temperature
= mass
= amount of heat
J/goC
oC
g
J
If data are given in initial (T1) and final (T2)
temperatures instead of change in
temperature, calculate ΔT using ΔT = T2 – T1

Model Problems A and B, pg. 376

Do Practice Problems #1 – 9 pg. 377


a) The Earth’s land or water surface heats up
as it absorbs solar radiation.
b) This thermal energy is transferred by
conduction to surrounding cooler air or
water causing convection currents in air
and
water

Convection (transfer of thermal energy in
fluids – liquids or gases)
Convection currents – air circulates and
distributes heat (remember warm air is less
dense, rises, cooler air descends and takes its
place close to the ground, it heats up…etc.

Different specific heat capacities of the
Earth’s different surfaces (sand, water,
forests, etc) affect how much they heat up the
air and water around them.
Why is the ice and water absorbing energy with
no change in temperature?

The Earth’s water absorbs a lot of heat from
the surroundings when condensing, and it
releases a lot of heat when it is evaporating.


Heat of vaporization (Hvap) is the amount of
thermal energy required to convert one mole
of a substance from a liquid to a gas
(evaportate it)
Heat of fusion (Hfus) is the amount of thermal
energy required to convert one mole of a
substance from a solid to a liquid (melt it)
Energy required for melting





Energy required for vaporizing
Q = nHfus
Q
n
Hfus
Hvap
amount of heat energy
number of moles
heat of fusion
heat of vaporization
Q = nHvap
J (joules)
(no units)
J/mol
J/mol

Practice Problems 10 – 18 pg. 383


The hydrologic cycle distributes water by
evaporation, condensation, and precipitation.
It transports thermal energy as well. When
water condenses, thermal energy is released,
when water evaporates it absorbs thermal
energy affecting weather and climate



Specific Heat Practice problems # 1-9 pg. 377
Heat of fusion and vaporization problems
#10-18 pg. 383
Questions: Pg. 387 #1,
pg. 398 #11, 12
(question # 13 gives you hints), 14, 16