Transcript Calculating Heat - Lompoc Unified School District / Home

Calculating Heat
Specific Heat
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Amount of heat energy needed to raise the
temp of 1 ml of a substance 1°C
For water the specific heat is 4.19 J/g °C, but it
is differenct for different substances
It takes 4.19 J to raise the temp of 1 g of water
1 °C
Every substance has a different specific heat
Table of Specific Heats
Calculating Heat When Substance
in One Phase
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Heat released or absorbed can be calculated by
multiplying three factors
Heat = specific heat x mass x temp change
q = c x m x Δt
Practice
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The specific heat of water is 4.19 J/ g C. How
much heat is needed to warm 350g of water
from 25 C to 75 C?
If 178 J of heat is needed to increase the
temperature of a 20g piece of copper metal
from 25 C to 48 C, what is the specific heat of
copper?
Heat and Phase Change
(Evaporation)
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Heat of vaporization (Hvao) energy required to
change one gram of a substance from liquid to
gas.
For water 2260J/g
Q = Hvao m
Practice
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The heat of vaporization of water is 2260J/g.
How much heat must be supplied to evaporate
50g of water?
How much heat is required to evaporate 150.g
of a substance at its boiling point if it has a
Hvap= 987 J/g?
Energy and Phase Change
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Heat of fusion (Hfus) energy required to
change one gram of a substance from solid to
liquid.
For water 340 J/g
Q = Hfus m
Examples
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The heat of fusion of ice at 0°C is 340J/g. How
much heat is needed to change 75g of ice at
0°C to a liquid at the same temperature?
The heat of fusion of water at 0°C is 340J/g.
How much heat is released when 250g of
water changes to ice at 0°C?
Practice
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How much heat is needed to change 100g of
water at 50C to steam at 120C? The specific
heat of water is 4.19 J/g C, the specific heat of
steam is 1.7 J/g C, and the heat of
vaporization of water is 2260 J/g.
How much heat must be released as 50g of
water at 25C to ice at -10C? The specific
heat of water is 4.19 J/g C, the specific heat of
ice is 2.1 J/g C, and the heat of fusion fro
water is 340 J/g.