Specific Heat Questions
1. Which kind of substance needs more energy to undergo a rise of 5 degrees in temperature - something with a high specific heat or something with a low specific heat? Explain.
2. How much heat in kilojoules has to be removed from 225 g of water to lower its temperature from 25oC to 10.0oC? (This would be like cooling a glass of lemonade.)
3. To bring 1.0 kg of water from 25 oC to 99 oC takes how much heat input, in joules? In kilojoules? This would be like making four cups of coffee.
4. Fat tissue is 85% fat and 15% water. The complete breakdown of the fat itself converts it to CO2 and H2O, and releases about 37.665 kJ/g (of fat in the fat tissue).

(a) How many kilojoules are released by a loss of 0.45 kg (1 lb.) of fat tissue in a weight-reduction program?

(b) A person running at 13 km/hr expends about 2.0 X 103 kJ/hr of extra energy. How far does a person have to run to "burn off" 0.45 kg of fat tissue by this means alone.
5. If a gold ring with a mass of 5.5 grams changes temperature from 25.0oC to 28.0oC, how much energy (in joules) has it absorbed?
6. The specific heat of helium is 5.188 J/goC and of nitrogen is 1.042 J/goC. How many joules can one mole of each gas absorb when its temperature increases 1.00oC?
7. We wish to determine how much heat paraffin gives off on burning. We use a candle flame to heat some water in a calorimeter. These data were obtained:

Mass of water in calorimeter 350 g
Initial mass of candle 150 g
Final mass of candle 112 g
Initial temperature of water 15oC
Final temperature of water 23oC

Calculate:
a) the temperature rise,
b) the joules absorbed by the water in the calorimeter,
c) the grams of paraffin burned,
d) the approximate value of heat of combustion of paraffin in J/g.
Neglect the energy absorbed by the calorimeter.
8. Ethanol has a heat capacity of 2.51 J/goC. 25.00 grams of this at 40oC has been used to heat 500 mL of water. What would have been the temperature change of the water if the alcohol ends up at 10oC?
9. Ethyl alcohol in a container is lit. The heat produced during burning was used to heat a flask of water. The data collected are shown below:

Mass of container plus ethanol, before burning 42.70 g
Mass of container plus ethanol, after burning 40.70 g
Mass of flask plus water 582.0 g
Mass of the empty flask 182.0 g
Initial temperature of the water 5.3o
Final temperature of the water 35.3oC
Calculate the heat of combustion of ethyl alcohol.
10.  100 grams of ethanol at 25oC is heated until it reaches 50oC.  How much heat does the ethanol gain?
11. A beaker contains 50 grams of liquid at room temperature.  The beaker is heated until the liquid gains 10oC.  A second beaker contains 100 grams of the same liquid at room temperature.  This beaker is also heated until the liquid gains 10oC.  In which beaker does the liquid gains the most thermal energy? Explain
12. You know that ΔT = Tf - Ti.  Combine this equation with the heat equation Q = mc ΔT to solve for the following quantities.
a)  Ti in terms of Q, m, c and Tf
b)  Tf in terms of Q, m, C and Ti
13. How much heat is required to raise the termperature of 789 grams of liquid ammonia from 25.0oC to 82.7oC?
14. A solid substance has a mass of 250.00 grams. It is cooled by 25.00oC and loses 4937.50 J of heat.  What is it's specific heat capacity.   Identify this substance.
15. A piece of metal with a mass of 14.9 grams is heated to 98.0oC. When the metal is placed in 75.0 grams of water at 20.0oC.  The temperature of the water rises by 28.5oC.  What is the specific heat capacity of the metal?
16.  A piece of gold ( c = 0.129 J/goC) with a mass of 45.5 grams and a temperature of 80.5oC is dropped into 192 grams of water at 15.0oC.  What is the final temperature of the system?
17. Whe iron nails are hammered into wood, friction causes the nails to heat up.
a)  Calculate the heat that is gained by a 5.2 gram nail as it changes from 22.0oC to 38.5oC?

b)  Calculate the heat that is gained by a 10.4 gram nail as it changes from 22.0oC to 38.5oC?

c)  Calculate the heat that is gained by a 5.2 gram nail as it changes from 22.0oC to 55.0oC?
18. A 23.9 grams silver spoon is put in a cup of hot chocolate.  It takes 0.343 kJ of energy to change the temperature of the spoon from 24.5oC to 85.0oC.  What is the specific heat capcacity of the silver?
19. The specific heat capacity of aluminum is 0.920 J/goC. The specific heat capacity of copper is 0.389 J/goC.   The same amount od heat is applied to equal masses of these 2 metals.  Which metal increases more in temperature?  Explain.
20. Explain why there is an energy difference between the following reactions.
CH4(g)  +  2 O2(g)  ----->  CO2(g)  +  H2O(g)  + 802 kJ
CH4(g)  +  2 O2(g)  ----->  CO2(g)  +  H2O(l)  + 890 kJ
           Answers