Science 10 Assignment 4.2 Key (39 marks)
1. Describe how thermal energy is transferred through the hydrosphere (2
marks)
Thermal energy is transferred through the hydrosphere by evaporation,
circulation and condensation.
2. Name three methods of thermal energy transfer. (3 marks)
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3. Identify the sources of water vapor in the atmosphere. (2 marks)
Some sources of water vapor in the atmosphere are plants, animals, bodies of
water.
4. State the percent of Earth’s surface that is covered by water. (1 mark)
About 71% of the Earth’s surface is covered by water.
5. Create a pie chart illustrating the sources of water vapour in the atmosphere.
(3 marks)
Water Vapour
Sources
Evaporation
Cellular
Transpiration
Photosynthesis
6. Define the term “specific heat capacity” (1 mark)
heat capacity - the number of heat units needed to raise the temperature of a
body by one degree
7. Identify the factors that must be considered in order to determine the specific
heat capacity of any substance. (3 marks)
a. The amount of energy added to a system
b. The mass of the substance present
c. The temperature change observed for the substance
8. The theoretical heat capacity of water is 4.19 J/g˚C. Aluminum has a
theoretical specific heat capacity of 0.897 J/g˚C. If 1.00 g of water and 1.00 g of
aluminum are both heated to 50.0 ˚C, which substance will contain the greater
quantity of thermal energy ? (1 mark)
The water will contain a greater quantity of energy.
9. Write an equation for the heat of fusion, and define each term in the equation
(3 marks)
∆Hfus = E/m
∆Hfus = Heat of fusion, E= Energy in joules or Kj, m=mass in grams or Kg.
10. Define the term “heat of vaporization” (1 mark)
- heat absorbed by a unit mass of a material at its boiling point in order to
convert the material into a gas at the same temperature
11. What is the difference between the heat of fusion and the heat of
vaporization of a substance. (2 marks)
The difference is one is the heat required to melt a substance and one is the
heat required to vaporize a substance.
12. Calculate the amount of thermal energy required to increase the temperature
of 3.00 kg of aluminum from 20.0 ˚C to 80.0 ˚C. The theoretical specific heat
capacity of aluminum is 0.897 J/g˚C. (5 marks)
∆H= ?, m= 3000 J, ∆t= 60 ˚C, c= 0.897 J/g˚C
∆H= mc∆t = (3000g)(0.897 J/g˚C)(60˚C)
= 1.61 x 105 J
13. Calculate the amount of thermal energy required to increase the
temperature of 2.00 kg of water by 20.0 ˚C. The theoretical specific heat capacity
of water is 4.19 J/g˚C. (5 marks)
∆H= ?, m= 2000 J, ∆t= 20 ˚C, c= 4.19 J/g˚C
∆H= mc∆t = (2000g)(4.19 J/g˚C)(20˚C)
= 1.68 x 105 J
14. Calculate the amount of energy absorbed when 45.0 g of ice at 0.0 ˚C melts.
The heat of fusion of water is 6.01 kJ/mol, and the molar mass of water is 18.02
g/mol. (5 marks)
M= 18.02 g/mol, m= 45.0 g, ∆Hfus = 6.01 kJ/mol, n= # of moles
n=m/M, = 45.0g/18.02 g/mol = 2.50 mol
∆H=∆Hfus•n = (6.01 kJ/mol)(2.50 mol) = 1.50 x 101 kJ
15. Explain why 100.0 g of liquid water at 100.0 ˚C contains less thermal energy
than 100.0 g of water vapor at 100.0 ˚C. (2 marks)
The 100 g of liquid water at 100.0˚C contains less thermal energy than 100.0 g
of water vapor at 100.0˚C because the amount of potential energy gain
required to vaporize water is stored in the water vapor.