Honors Chemistry
Name: ________________________________________ Date: _________________ Mods: ___________
Specific Heat & Calorimetry (In-Class Examples)
Measuring heat (formerly measured in calories) is called calorimetry. Now we measure heat energy in
joules (J) which also serves as the SI unit. The equation we use to measure heat is:
q = m·cp·T
q = heat energy
m = mass of water
cp = the specific heat capacity
T = the change in temperature (in °C or K)
1)
Water has a specific heat capacity of 4.184 J/g·°C. This means that it takes 4.184 J to heat 1.00
gram of water 1.00°C. How much energy is needed to heat 30.0 g H2O from 10.0 °C to 50.0 °C?
2)
What amount of heat is released when 175 mL of water (recall the density of water = 1.0 g/mL)
cools from 100°C to room temperature, 20.0°C?
What would this amount be in calories?
4)
We don’t always have to work with water. The specific heat capacity of copper is 0.39 J/g·°C.
Therefore, it is ____________________ (easier/more difficult) to heat up copper than to heat up
water.
How much energy would it take to heat up a 5.20 g sample of copper from 20.0 °C to 100.0°C?
5)
A piece of stainless steel weighing 1.55 g absorbs 141 J of heat when its temperature increases by
78°C. What is the specific heat of stainless steel?
Signs of T and q:
 q means heat is released. + q means heat is absorbed.
T is always final temperature – initial temperature.
If something is getting hotter (10°  30°) the T is 30 – 10 = + 20°. (heat is absorbed) = endothermic
If something is getting cooler (75°  25°) the T is 25 – 75 =  50°. (heat is released) = exothermic
Determining Specific Heat Capacity of a Substance Using Calorimetry
6)
A 9.6 g sample of a metal alloy is heated to 102.3°C and then dropped into 27.0 g of water in a
calorimeter. The temperature rises from 23.5°C to 29.2°C. What is the specific heat of the metal
alloy?
Determining Final Temperature of the System & Surroundings Using Calorimetry
8)
Suppose we mix 90.0 grams of hot water at 90.0°C with 10.0 grams of cold water at 10.0°C.
Solve for the final temperature of the mixture when the system is in thermal equilbrium.
Specific Heat & Calorimetry (Homework)
1) If a 50.0 g piece of glass was initially at 20°C, what will be the final temperature if the glass absorbs
5.275 kilojoules of heat and has a specific heat of 0.50 J/g°C?
2) Calculate the heat capacity of a piece of wood if 1500.0 g of the wood absorbs 6.75×104 joules of heat,
and its temperature changes from 32°C to 57°C.
3) 100.0 mL of 4.0°C water is heated until its temperature is 37°C. If the specific heat of water is 4.184
J/g°C, calculate the amount of heat energy needed to cause this rise in temperature.
4) If 55 calories of heat were needed to raise the temperature of ice from – 58oC up to – 29oC, what must
have been the mass of ice sample that was heated? The specific heat of ice is 2.108 J/g°C.
5) What is the specific heat capacity of silver metal if 55.00 g of the metal absorbs 47.3 calories of heat and
the temperature rises 15.0°C?
6) The specific heat of iron is 0.46 J/g.°C. If 13.8 kJ of heat is applied to a 324 g piece of iron, what will be
the temperature change for the sample?
7) Supose you have two separates samples: 5.00 grams of ethanol (Cp of C2H5OH = 2.44 J/g°C ) and 5.00
grams of water. Both the ethanol and the water initially start at the same temperature of 10.0°C. If each
sample is individually heated with 300 J of energy, determine the final temperature of the water sample
and the final temperature of the ethanol sample. How does the specific heat of each sample affect their
final temperatures when the same quantity of heat was added?
8) 50.0 g of iron that has an initial temperature of 225 ºC and 50.0 g of gold that has an initial temperature
of 25.0 ºC are brought into contact with one another. Assuming no heat is lost to the surroundings, what
will be the final temperature when the two metals reach a thermal equilibrium? (specific heat capacity of
iron = 0.499 J/gºC and gold = 0.128 J/gºC)
9) A 14.7 g sample of a metal alloy is heated to 96.8 ºC and then dropped into 20 g of water in a
calorimeter. The temperature of the water rises from 22 ºC to 24.1 ºC. What is the specific heat of the
metal?
10) 175 grams of hot aluminum (100ºC) is dropped into an insulated cup that contains 40.0 g of ice cold
water (0.0ºC). Determine the final temperature, TF, if the heat capacity of water is 4.184 J/gºC. The
specific heat of aluminum is 0.90 J/gºC.
11) A 15.5 g sample of a metal alloy is heated to 98.9°C and then dropped into 25.0 g of water in a
calorimeter. The temperature of the water rises from 22.5°C to 25.7°C. What is the specific heat of the
metal alloy?