Section 5.6: Present and Future Energy Sources
Research This: Deep Lake Water Cooling, page 329
A. Answers may vary. Sample answer: DLWC has minimal effects on the aquatic
environment because the water that is removed is not returned to the lake after it has been
used for cooling, but is used for Toronto’s water supply. There is some disruption of
aquatic habitats as a result of laying the underwater pipes that are necessary for the
process to work. I believe it can be considered a green energy source because it is
renewable, that is, it does not use up a resource, it will result in a 75 % decrease of
greenhouse gas emissions, and it does not create other toxic or hazardous byproducts.
B. No, DLWC does not take water away from Lake Ontario. The water that is used for
cooling is water that is destined for the city’s water supply, so it would be removed from
the lake anyhow.
C. Answers may vary. Answers should include:
(a) Both DLWC and cooling systems that use energy from fossil fuels result in cooling
the air in a building by transferring thermal energy from the air to another medium.
(b) While DLWC produces slightly warmer water as its only significant product, cooling
systems that rely on fossil fuels produce greenhouse gases and often other wastes as well,
for example, cooling fluids.
(c) DLWC causes minimal disruption to aquatic habitats and does not pollute air or
water. Cooling systems that rely on fossil fuels do pollute the air and extracting the fossil
fuels from the Earth can be extremely disruptive to plant and animal habitats.
Section 5.6 Questions, page 330
1. Answers may vary. Sample answers:
(a) Nuclear fusion is the process in which smaller nuclei join to form larger nuclei.
Nuclear fusion currently is not used to generate energy on Earth because the technology
required to harness the large quantity of energy released during fusion does not currently
exist.
(b) Ethanol is a commonly used biofuel produced by fermenting sugars. Ethanol is not as
volatile as gasoline and therefore cannot be used directly as a fuel source in most
automobile engines. Alternatively, an ethanol-based biofuel, E85, which is 85 % ethanol
and 15 % gasoline, can be used in vehicles with specially designed engines.
(c) Syngas is a synthetic fuel produced from the gasification of coal. It is a mixture of
carbon monoxide gas and hydrogen gas that can be used in the place of other fossil fuels.
The burning of syngas is more efficient than the burning of coal. These fuels can extend
the limited supply of fossil fuels.
(d) Coal slurry is a fuel consisting of pulverized coal mixed with water. Coal slurry can
directly replace some petroleum-based fuels. For example, it can be used directly in an oil
furnace as fuel.
2. Energy changes associated with nuclear fission and fusion processes are much greater
than energy changes associated with chemical reactions or physical processes.
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Chapter 5: Thermochemistry
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3. Answers may vary. Sample answer: The statement that said that the energy we get
from fossil fuels came from the Sun is true. Fossil fuels form from the decaying remains
of plants and animals, which are then subjected to high temperatures and pressures
beneath Earth’s surface for thousands of years. Animals get their energy from either
plants or other animals that eat plants, and plants get their energy from the Sun through
the process of photosynthesis. The process of photosynthesis converts captured solar
energy to chemical energy.
4. Answers may vary. Sample answer: The advantages of burning coal and gasoline for
energy are mainly lower production costs, convenient storage, and easy transportation.
Coal and gasoline are easily available and both release more energy during combustion
than other fuels. Coal is a fossil fuel formed from decaying plant matter that has been
buried for millions of years. Gasoline is collected from fractional distillation of crude
petroleum. Currently all the infrastructure is built and has been in operation for more than
half a century, from the drilling to the transport of the fuel to the refining process all the
way to the consumer purchase of the fuel. The combustion of coal and gasoline produces
carbon dioxide gas and water vapour, which are released into the atmosphere where they
contribute to global warming and climate change. Climate change has been shown to lead
to loss of species due to changes in habitats. The burning of these fuels also releases other
pollutants. For example, the combustion of coal that contains high quantities of sulfur
releases sulfur dioxide gas, SO2(g), which leads to acid precipitation. Extracting and
transporting fossil fuels can be dangerous, as we have seen in recent global events, such
as the 2010 oil leak in the Gulf of Mexico.
5. The burning of gasoline releases 14.9 kJ more energy per gram than burning coal.
This makes gasoline more efficient as more energy is produced from the same mass of
fuel.
6. (a) Answers may vary. Sample answer: The high per person energy usage in Canada
could be due to the cold climate and heavy industries.
(b) Answers may vary. Sample answer: Canadians could reduce their energy
consumption by using low energy consumption transportation methods, taking control of
temperature and use appliances efficiently. For example, whenever possible, walk, bike,
car pool, or use mass transit; set your thermostat in winter to a lower temperature; switch
to the use of energy-efficient appliances and turn off appliances at times when they are
not in use. However, using mass transit is not possible when it is not available. You need
to put on more clothing in winter when the thermostat is set to a lower temperature.
Energy-efficient appliances are usually more costly. For certain appliances, such as the
refrigerator, they should not be turned on and off as desired.
7. (a) The advantages of using hydrogen as a fuel source for cars are that hydrogen has a
high enthalpy of combustion and that the only product of its combustion is water vapour.
Hydrogen gas releases about 2.5 times the quantity of energy per gram released by the
combustion of natural gas. Water vapour is not an air pollutant so hydrogen is a very
clean burning fuel.
(b) Hydrogen cars are not a viable option at this time because the fuel used—hydrogen
gas—is currently very expensive to produce and challenging to transport and store.
(c) Answers may vary. Students’ answers should include reasoning around cost and
efficiency of production, storage, and transport of hydrogen gas.
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Chapter 5: Thermochemistry
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8 (a) Answers may vary. Sample answer: According to the Toronto Hydro website, the
sources of electrical energy that power the city of Toronto are burning coal, nuclear
power, hydroelectric energy, burning natural gas, and renewable energy sources.
(b) Answers may vary. Sample answer: According to the Toronto Hydro website these
power sources deliver 24 746 GW-hours (gigawatt-hours) (W = J/s) of power for the city
of Toronto.
(c) Answers may vary. Sample answer: As of 2012, according to the city of Toronto
website, one of the alternative energy programs in the city is the SolarCity Program. The
SolarCity program promotes the use of solar thermal and photovoltaic generation
equipment on city and community-owned facilities and residences. Solar power can
displace emissions from fossil fuels used for electricity generation or heating, especially
during periods of peak summer energy demand when air quality may also be at its worst.
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Chapter 5: Thermochemistry
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