Honors Chem: Calorimetry Mini Unit
Name____________________
Heat (q)

Heat:
o
If T1 > T2
q sys =
q surr =
If T1 < T2
q sys =
q surr =
Calorimetry: the measurement of heat flow
-- device used is called a...
specific heat capacity (C): amt. of heat needed to raise temp. of 1 g of a substance 1 oC (1 K)
--
For energy changes involving…
heat of fusion (ΔHfus):
heat of vaporization (ΔHvap):
We can find the heat a substance loses or gains using:
where
q = heat
m = mass of substance
C = substance’s heat capacity
T = temperature change
ΔH = heat of vaporization/fusion
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Temperature Change within phase
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depends on heat capacity of phase
C H2O (l) =
C H2O (s) =
C H2O (g) =
Phase Changes (s ↔ l ↔ g)
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•
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overcoming intermolecular forces
ΔHfus =
ΔHvap =
From Ice to Steam in Five Easy Steps
q1: Heat the ice to 0°C
q2: Melt the ice into a liquid at 0°C
q3: Heat the water from 0°C to 100°C
q4: Boil the liquid into a gas at 100°C
q5: Heat the gas above 100°C
q tot =
Heating Curve Practice
1. How much energy (J) is required to heat 12.5 g of ice at –10 oC to water at 0oC?
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2. How much energy (J) is required to heat 25.0 g of ice at –25 oC to water at 95 oC?
3. How much energy (J) is removed to cool 50.0 g of steam at 115 oC to ice at – 5.0 oC?
Food and Energy
1 calorie =
1000 calories =
or…
Does water have negative calories?
How many Calories (nutritional) will you burn by drinking 1.0 L of water, initially at 36.5 oF (standard
refrigeration temperature)? Assume that the body must expend energy to heat the water to body
temperature at 98.6 oF
Heat Transfer Experiments
Much calorimetry is carried out using a coffee-cup calorimeter.
-- If we assume that no heat is lost to the surroundings, then the energy absorbed inside
the calorimeter must equal the energy released inside the calorimeter.
i.e.,
1. A 75.0 g piece of lead (specific heat = 0.130 J/g-oC) initially at 435oC is set into 125.0 g of
water initially at 23.0oC. What is the final temperature of the mixture?
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2. A 97.0 g sample of gold at 785oC is dropped into 323 g of water, which has an initial
temperature of 15.0oC. If gold has a specific heat of 0.129 J/goC, what is the final
temperature of the mixture?
Challenge Problem: A 23.6 g ice cube at –31.0oC is dropped into 98.2 g of water at 84.7oC. Find the
equilibrium temperature. KEY =
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