Chapter 8: Water and Solutions

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Chapter 8: Water and Solutions
Mini Investigation: Designs and Detergents, page 369
A. The food colouring in water spread outward faster than it did in milk. The addition of
detergent to the milk plate created swirls of colour that were not observed in the dish containing
only water.
B. The spreading of the colour when the detergent was added to the milk suggests that the
molecules within the plate were set in motion by the addition of the detergent.
C. Milk contains water, fat, proteins, and other nutrients. Since the swirling of colours was
observed only in milk, we can attribute the observed changes to the fat and proteins.
D. Fat and protein molecules may have moved in response to the addition of detergent. This
movement must have caused the molecules in the food colouring to move.
E. Detergents can be used to disperse or breakup oil spills.
F. An emulsifier or emulsifying agent is a substance that facilitates the blending of two
immiscible substances, such as oil and water, into one phase. Mustard powder and egg yolk
contain a number of emulsifiers. Emulsifiers typically contain a hydrophilic (“water-loving”) end
and a hydrophobic (“water-hating”) end. The hydrophobic end forms attractions with fats while
the hydrophillic end attracts water. These attractions help to breakdown the phase boundary
between two immiscible liquids. Emulsifiers are used to make creams, lotions, and detergents.
Section 8.1: The Importance of Water
Research This: What Is Your Water Footprint, page 373
A. Answers may vary. Sample answer: I predict my annual water footprint for a year is
490 m3.
B. Answers may vary. Students may find that their calculated value was much greater than their
predicted value. Sample answer: My calculated water footprint for a year was 1555 m3. This
value more than three times my predicted value.
C. Answers may vary. Sample answer: Two reasonable lifestyle changes that could significantly
reduce my water footprint include having shorter showers and operating the dishwasher and
washing machine only when they are full.
D. Answers may vary. Sample answer: The use of water should be carefully controlled
regardless of whether or not you live near a large body of fresh water. Wastewater from homes
must be treated before it is returned to the environment. This adds to the energy cost of the
municipality that operates the water treatment process. Furthermore, a significant amount of the
energy required to treat the water is generated using non-renewable and polluting resources, such
as coal and natural gas.
Section 8.1 Questions, page 375
1. Oxygen has a greater electronegativity than sulfur, which means that the oxygen-to-hydrogen
bond in water is more polar than the sulfur-to-hydrogen bond in hydrogen sulfide. As a result,
hydrogen bonding exists between water molecules while dipole–dipole attractions exist between
hydrogen sulfide molecules. Since hydrogen bonds are stronger than dipole–dipole attractions,
water has a higher boiling point than hydrogen sulfide. As a result, water is a liquid at room
temperature while hydrogen sulfide is a gas at room temperature.
2. Water has high surface tension, which is the property illustrated in Figure 6.
Copyright © 2011 Nelson Education Ltd.
Chapter 8: Water and Solutions
8.1-1
3. Table 2 Beneficial and Unusual Examples of the Properties of Water
Property
Beneficial and Unusual Examples
high melting and boiling points
• water naturally occurs as a liquid
• body fluids are liquid over large range of
temperatures
expansion when cooling from 4 °C to 0 °C
• ice floats on water
• allows aquatic life to continue since water
freezes from the top down
high surface tension
• makes it possible for capillary action to occur
• drop of water has a spherical shape
ability to exchange thermal energy with little
• maintains a moderate climate in coastal areas
change in temperature
• can be used as a coolant to prevent engines
from overheating
inability to mix with non-polar compounds
• oil does not mix with water, which allows oil
spills to be cleaned up
• enables organisms to retain water within a
waterproof coating
4. (a) An aquifer is a layer of rock or sediment that holds water and allows groundwater to flow
through it.
(b) The rate at which we can pump water from an aquifer is limited by the rate at which the
groundwater is replaced. Removing too much water too quickly from an aquifer will drain the
aquifer. This process in not entirely sustainable.
(c) It is important to consider water flow patterns before constructing a mine or an oil refinery in
an area because industrial demand affects the water supply. The industry will be using the water,
which means that it will be unavailable for other uses. Industrial processes can also contaminate
the water.
5. Evaporation results in clean water because solutes are left behind as the water evaporates.
When the evaporated water condenses, it is very pure.
6. Answers may vary. Sample answer: In-ground irrigation systems waste less water because
they deliver water directly to the plants. There is also less water evaporation. Above-ground
sprays waste more water because there is loss of water through evaporation and all areas, not just
the plants, receive the water.
7. Answers may vary. Sample answer: The criticism of bottled-water companies for draining
large volumes of water from local freshwater supplies is valid. Bottled-water companies fill
plastic bottles with water taken from local springs, aquifers, or other water sources. This water is
trucked to different locations other than the original location of the water. Water is also used in
the manufacturing of the plastic bottle. This means that large volumes of water are involved in
the manufacturing and production of water bottles. The defense that soft-drink manufacturers use
far more water than the bottled-water industry is not valid. Although soft drinks contain
carbonated water, they are not 100 % water.
8. Changing to a vegetarian diet may reduce a person’s overall water footprint because the need
for water to raise livestock is reduced. However, vegetarians still have the same water
requirements for showering, washing dishes, and washing clothes.
9. Global warming might reduce the availability of fresh water because of the increased rate of
evaporation. This will impact the amount of water available to replenish groundwater supplies.
As well, evaporation may reduce the amount of surface water available.
Copyright © 2011 Nelson Education Ltd.
Chapter 8: Water and Solutions
8.1-2
10. Answers may vary. Sample answer: Five changes that can be made to reduce a household’s
overall water consumption include taking fewer showers per week, turning off the water when
brushing teeth, watering the lawn only when it needs it during the summer months, installing
water-saving shower heads, and turning off the water when rinsing dishes by hand. I am willing
to make these changes because they are easy to do and will not impact my life very much.
11. Answers may vary. Sample answer: One advantage of the privatization of water treatment
and distribution is that private companies are more efficient than government because of free
market competition. This means that private companies could provide improved water quality,
lower prices, and quicker delivery. Private companies are motivated to see their businesses
succeed so profits are typically invested back into the company to allow for further research and
development. The disadvantage is that many people see water as a right that should be available
to everyone. Private companies are interested in profits, which may mean increased costs to the
consumer. These costs may restrict access to water for lower-income groups.
12. Answers may vary. Sample answer: People in Egypt receive their water from the Nile. They
also receive water from aquifers in the desert. Historically, people obtained water from the Nile.
The problems facing Egypt is that population growth is leading to water scarcity. The quality of
the water is also decreasing, leading to human health problems and the contamination of
groundwater.
Copyright © 2011 Nelson Education Ltd.
Chapter 8: Water and Solutions
8.1-3
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