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Energy and Heat Review Sheet
1. What is the relationship between the rate of cooling of a substance and the specific heat of that
substance? The higher the specific heat number, the slower it is to cool (or heat up)
2. What is the formula for calculating heat?
Q = m Cp T
3. What is the formula for calculating specific heat? Cp = q/ m T
4. In the above formulas, what does each of the following represent and what are the units for each?
a.
b.
c.
d.
q=
m=
Cp =
T =
heat
mass
Specific Heat
Change in Temp.
units - Joules
units - grams
units – J/g oC
units - oC
5. What are the 2 units that can be used to measure heat? Joules and calories
6. A 1000 g piece of a metal at a temperature of 157oC is placed into a container of 2500 g of water at a
temperature of 25oC. The final temperature of both the metal and the water is 45oC.
a. What will happen to the temperature of the piece of metal? decrease
b. What will happen to the temperature of the water? increase
c. What is the specific heat of the metal?
Q = m Cp T
2500 g * 4.184 j/goC * 20oC = 209200.0 J
Cp = Q / m T
209200 J / (1000g * 112oC) = 1.87 j/goC
7. What is the study of heat change that occurs in chemical reactions called? theromchemistry
8. What is the capacity to do work or supply heat called? Energy
9. What type of reaction has heat being transferred from the system to the surrounding? Exothermic
10. What type of reaction has heat being transferred from the surrounding to the system? Endothermic
11. What 2 variables will affect a substance’s heat capacity? Amount of substance and type of substance
Use the following chart to answer the questions
Substance (all 100 g)
Iron
Gold
Salt
Mercury
Specific Heat (J/goC)
0.450
0.129
0.864
0.140
12. Which of the above substance would change from 100oC to 50oC the slowest? Salt – highest S.H.
13. Which of the above substances would take the longest to heat up from 25oC to 75oC? Salt
14. Which of the above substances would require the most heat energy to raise its temperature? Salt
15. Which of the above substances would require 0.864 J of energy to raise 1 gram of the substance 1
degree C? Salt
16. What is the specific heat of a substance if 202 J is required to heat 44.0 g of the substance from 22oC
to 33.6oC?
Cp = q/m T
202J / (44.0 g * 11.6 oC) = 0.396 J/goC
17. How much heat energy is required to raise 40 g of iron from 25oC to 75oC? (use chart to find
specific heat of iron)
Q = m Cp T
40g * 0.450 j/goC * 50oC = 900 J
18. What is the specific heat of a substance, with a mass of 62.5 g and at a temperature 100oC, that raises
the temperature of 325g of water from 30.5oC to 38.8oC?
Water Q = m Cp T
325 * 4.184 * 8.3 = 11286.34 J
Substance -
Cp = q/m T
11286.34 / (62.5 * 61.2) = 2.95 J/goC
19. What is the specific heat of a metal, if, when 57.3 g of the metal at 99.4oC is dropped into 195 g of
water at 21.6oC the temperature increases to 27.1oC?
Water Q = m Cp T
195 * 4.184 * 5.5 = 4487.34 J
Substance -
Cp = q/m T
4487.34 / (57.3 * 72.3) = 1.083 J/goC
20. You have a 357.3 g sample of a metal in a hot water bath with a temperature of 92.6oC. Your
calorimeter has 775 g of water at a temperature of 23.9oC in it. You remove the metal from the hot
water bath and place it in the calorimeter. The temperature of the water increases to 29.9oC.
a. What is the t of the water? 6.0 oC
b. What is the t of the metal? 62.7oC
c. What is the heat gained by the water? 19455.6 J
d. What is the specific heat of the metal? 0.868 J/goC