unit water systems d - chalkdust: mr. caruso grade 8 · sci8_unitd_chap10.indd 258 10/24/08...

D258 Unit D • Water Systems NEL

WATER SYSTEMSUNIT

Sci8_UnitD_Chap10.indd 258Sci8_UnitD_Chap10.indd 258 10/24/08 11:57:02 AM10/24/08 11:57:02 AM

BIG Ideas

Water is crucial to life on Earth.

Water systems infl uence climate and weather patterns.

Water is an important resource that needs to be managed sustainably.

259NEL

Unit Preview

Th ere is water almost everywhere on Earth, but is there enough? Ontario and the rest of Canada have a plentiful supply of water. However, this supply is fragile and must be monitored to ensure that water will be available for future generations. Water is a renewable resource only if we take care of it. Do you think that washing cars by hand is a careful use of our water supply?

In contrast to our plentiful water supply in Ontario, over 1 billion people worldwide do not have access to clean water. Every 15 seconds, a child somewhere in the world dies from a lack of clean water.

How can we tell when the water supply is under threat here in Canada? Some regions experience frequent summer droughts. Lake levels fall. Farmers are unable to irrigate (water) their crops. Water wells become polluted. Householders fi nd themselves under a “boil water advisory.”

What is the solution to a lack of clean water? Can we solve the problem by changing our behaviour? Can we stop wasting water? Can we become stewards of this valuable limited resource? If we care for our water supply, it will be available for future generations.

CHAPTER 0 Safe Drinking Water

CHAPTER a Water Quality

CHAPTER b Water, Weather, and Climate


Discover Science and Technology

UNIT D

260 Unit D • Water Systems NEL


261NEL

Felicia’s older brother Brad works with a Canadian organization called World Water. Th is organization helps people who do not have access to clean drinking water. Volunteers work mostly in developing countries. Th ey show the local people how technology can improve their access to clean water. World Water aims to

partner with communities in developing • countries to build their technological knowledge and skillsmake Canadians aware of how they aff ect • communities in developing countriesencourage the Canadian government to take • a leadership role in developing countriesBrad works in Malawi as part of a water and

sanitation team. Th e team focuses on Malawi’s rural areas where most of the population lives without clean water for drinking. Brad helps to build water treatment and sanitation facilities. He also teaches people how to use and maintain the facilities properly. His team works with local communities and with the government of Malawi. Brad believes that this process will keep the technology working long aft er the volunteer team leaves.

World Water is collecting data to monitor and evaluate its projects. Th e organization wants to be sure that the number of waterborne diseases in partner communities decreases. Brad is proud of his successes in Malawi. He likes World Water’s model of designing and building technological solutions. He hopes that this model will be used in other regions and by other organizations.

Critical LiteracyWhen they write, authors sometimes express their beliefs about the world. Readers can analyze these messages by asking themselves why, how, and for whom a text was written. They can also try to see whose point of view is represented, and whose point of view is silent. Think about the following questions.

How does• this story highlight unfairness in the world? Who has access to clean water? Who does not? Why?

If we could read or hear an interview with a Malawian • villager, what do you think he or she would have to say about water? Describe his or her point of view.

World Water is helping to reduce • unfairness in the world. What other organizations are working towards this goal? Discuss with a partner.

L I N K I N G T O L I T E R A C Y


UNIT D

262 Unit D • Water Systems NEL

Let’s Get Started

1. Work in groups of three or four. Each group needs two large pieces of chart paper and two markers of diff erent colours. Write “How I Use Water” at the top of one of the pieces of paper.

2. Brainstorm how each of you uses water in the school, at home, and in the community. List all these uses of water on your chart paper.

3. Divide your second piece of chart paper into two columns. Write “Essential water uses” at the top of the left -hand column, and “Non-essential water uses” at the top of the right-hand column. In your group, consider each water use that you listed on the fi rst piece of chart paper, and decide whether each type of use is “essential” or “non-essential.” You may decide, for example, that using water to brush your teeth is “essential,” but that using water to mix with orange juice concentrate is “non-essential” (Figure 1).

4. Once you have made all your decisions and completed your chart, begin a gallery walk. One member of your group stays with your charts to explain your group’s lists to the visiting groups. Th e rest of your group walks around to look at other groups’ charts.

5. Visiting groups can suggest additions to your “How I Use Water” page, identifying water uses that your group might not have considered. Th e host student records the new suggestions using a diff erent-coloured marker.

6. When your group returns to your home area, review each new suggestion. Again, decide whether it belongs in the “essential” column or the “non-essential” column.

7. Be prepared to defend your “essential” water uses in a class discussion. Your classmates may try to convince you that some of your uses were really not essential.

8. On your own, answer the questions below.(a) What have you learned from this activity

about how North Americans use their water resources?

(b) Do you think you are a typical North American when it comes to water use? Explain your answer.

Th ere is plenty of clean water in most parts of North America. Does this mean that we can use as much water as we want, with no thought to the consequences? Do we sometimes use more water than we should? In this activity, you will see if there is any truth to these ideas.

Exploring the Uses of Water

Essential water uses Non-essential water usesbrushing my teeth making orange juice from concentrate

Figure 1


Water is important for everyone. However,

people in some regions of the world do not have

access to clean water. How would your life be

diff erent if you no longer had access to clean

water? Do you think you might be able to help

people in areas that have no access to clean

water? We must all treat Earth’s water resources

in a sustainable way. In this unit, you will learn

about how you can help achieve this goal.

In the Unit Task, you will fi nd out about an

award that is being off ered for a solution to a

problem involving water. You will choose an issue

that may be aff ecting a water source anywhere in

the world. You will be asked to prepare and test

an action plan to address the issue. Or, you may

design, build, and test a prototype of a device

that solves a water problem. Whichever option

you choose, you will collect data during trials.

You will then use your data in a news media

release that describes the success of your action

plan or device.

Solving a Water Issue

Unit Task Preview

263NEL

By the end of the Water Systems unit, you will be able to demonstrate your learning by completing this Unit Task. As you work through the unit, continue to think about how you might meet one of these challenges. Read the detailed description of the Unit Task on page 338, and look for the Unit Task icon at the end of selected sections for hints related to the task.

Unit Task

• choose an appropriate issue to address

• prepare your action plan or design your device

• test your action plan or build and modify your device

• write your media release

You will be assessed on how well you

Assessment


CHAPTER

264 Chapter 10 • Safe Drinking Water NEL

Safe Drinking Water

KEY QUESTION: Where does water come from?

Looking Ahead

We use water in many different ways every day.

Water circulates around Earth in the water cycle.

The skills of analysis can be used to determine personal water use and ways to reduce water use.

Water must be treated before it is safe to drink.

The skills of technological problem solving can be used to design and build a simple water fi ltration device.

The media report on water-related issues in different ways.

VOCABULARY

water cycle

melting

sublimation

evaporation

condensation

deposition

freezing

runoff

groundwater

aquifer

water table

precipitation

polar ice sheet

icecap

glacier

water treatment

fl oc

sustainability

10


The following traditional story is from the Mi’kmaq (Micmac) and Maliseet First Nations of Nova Scotia.

Once there was a great drought. Th e rain stopped falling and the earth became dry. Finally the streams stopped fl owing. Th ere

was a village by the side of the stream. A villager was sent upstream to fi nd out why the stream had stopped fl owing. Before long, the man came back. “Th ere is a dam across the stream,” he said. “It is holding back all the water. Th ere are guards on the dam. Th ey say their Chief is keeping all the water for himself.”

“Go and beg him for water,” said the Elders of the village. “Tell him we are dying without water to drink.” So the villager went back again. When he returned, he held a bark cup fi lled with muddy water. “Th is is all the water their Chief will allow us to have,” he said.

Th ey were not sure what to do. Th en one of the old Chiefs spoke. “We must pray to Gitchee Manitou,” he said. “Perhaps he will pity us and send help.” Th en they burned tobacco and sent their prayers up to the Creator. Th eir prayers were answered when Gitchee Manitou sent his friend Koluscap down to the village. Koluscap took the shape of a tall warrior who used a tall pine tree for a club. He struck the dam with his club. Th e dam burst, releasing all the water. Once again, water fl owed down the stream and into the village. Some of the villagers were so happy they jumped into the stream and dove so deep that they became water creatures, replacing those that had dried up and died when the dam was built. Th ey still live in that stream today, sharing the water that no one person can ever own.

(Adapted from “Koluscap and the Water Monster” from Keepers of the Earth)

Text Genre: LegendsLegends are traditional cultural stories that have been passed on from one generation to the next for many years. Legends were originally created to explain natural phenomena or things that people believe. Many legends tell how characters overcame challenges and performed extraordinary deeds.

1 Which features of a legend does this story have?

2 What is one “cause” and one “effect” in this legend?

3 Create a story map of the events in the legend.


265NEL

Reading Science and Technology



PERFORM AN ACTIVITY10.1Personal Water UseYou have learned about systems and how they work. You know that a system is a group of parts that function together to perform a desired task. Now, you are about to fi nd out about the water system. All water on Earth is part of the water system.

Th e total amount of water on Earth is constant. If water is removed from one location, it must go somewhere else. We have access to plenty of water in North America. We oft en take this resource for granted. Some of us misuse, overuse, or even abuse the water supply. How much water do you think you use in a day (Figure 1)? Let’s fi nd out.

Questioning Hypothesizing Predicting Planning Controlling Variables

Performing Observing Analyzing Evaluating Communicating

SKILLS MENU

PurposeTo calculate your estimated personal water use in a 24 h period.

Equipment and Materials empty 1 L container• timing device•

Procedure1. Copy Table 1 into your notebook, leaving

10 or more empty rows before the “Grand Total” row.

Table 1 Tracking and Recording Personal Water Use

empty 1 L container timing device GRAND TOTAL

1 2 3 4 Ways in which Estimated volume Number of times Total estimated volume you use water per single use (L) per day used per day (L) brushing teeth 2 2 4

Figure 1 Brushing teeth is just one of the many ways water is used. How do you use water?

Reading Procedural TextProcedural text is used when the reader needs to follow instructions to complete a task. A new cellphone comes with instructions on how to download ring tones, music, and even videos. Instruction booklets are procedural texts. Procedural text always has a purpose, often requires the manipulation of equipment, and asks the reader to follow a series of steps to complete a task.



10.1 Perform an Activity 267NEL

2. In column 1 of Table 1, list all the ways in which you use water in a typical day.

3. Turn on the tap and let it run as fast as you would for tasks such as getting a drink of water or washing your hands. Use a stopwatch or clock with a second hand to determine how much time it takes to fi ll a 1 L container with water (Figure 2).

4. For each of the uses of water that you listed in column 1, estimate how much water you use. To help you make your estimates, time how long you run water from the tap for each task. Record your estimates in column 2.

5. In column 3, record the number of times per day you perform each task.

6. Using your values in columns 2 and 3, calculate the total estimated volume of water used per day for each task. Record these values in column 4.

Analyze and Evaluate(a) When the 24 h period is over, add the total

estimated volumes of water in column 4. Record the grand total at the bottom of Table 1.

(b) Classify the various tasks in which you used water. Use the categories “essential” and “optional.” Essential tasks are those that are important and must be done, such as drinking and brushing your teeth. Optional tasks are those that do not have to be done, such as using water for outdoor fun (Figure 3).

(c) Determine the estimated total volumes of water used in 24 h for “essential” tasks and for “optional” tasks.

(d) Calculate the percentage of your estimated daily water use that is used for “essential” tasks and for “optional” tasks.

(e) On average, Canadians use about 330 L of water a day. Do you use more or less than this?

(f) Based on your analysis, do you think you use too much water in one day? Explain why or why not.

Apply and Extend(g) Suggest one or two ways in which you could

reduce your water consumption. (h) Assume that you do not have any plumbing

in your house. You have to walk 1 km to the nearest source of drinking water. How would your water use change? List several things you would do diff erently.

2.B.7.2.B.7.SKILLS HANDBOOK

Figure 3 Is having a water fi ght a good use of our water resources?

Figure 2 Step 3

How can you use the skills that you developed in this activity to solve a water issue?Unit Task



10.2 What Is Water?Water is a very useful substance. Most major towns and cities are built near large bodies of water. We drink water, play with water, put out fi res with water, and irrigate crops with water (Figure 1). All living things need water.

Describing WaterImagine a glass of water at room temperature. You would probably describe it as a liquid that has no colour, taste, or odour.

Many substances dissolve in water, including table salt, sugar, oxygen, and carbon dioxide. Th is is one reason why water is so important for life. Plants and animals are largely made up of water. Over half of the human body is water.

Water in the body helps to transport substances to all the tissues and organs. Water is an important solvent in which essential chemical reactions can take place. Water also keeps us cool: as sweat evaporates, it transfers thermal energy away from the body. A person can live for over a month without food, but a person can live for only a few days without water. A supply of clean water is essential for our health.Is Water a Pure Substance or a Mixture?Pure water is clear, colourless, and has no taste or odour. You might have noticed, however, that natural bodies of water can appear to be blue or green, or even an unpleasant grey colour. Perhaps you have noticed that water from diff erent locations can taste diff erent or have an odour. Th is is because most of the water in nature is not pure. Rather, it is a mixture of pure water and other substances. Dissolved substances in water can give it colour, taste, and odour. Some of these substances are desirable. Other substances are dangerous. In Section 11.2, we will look at some of the substances that dissolve in water.

Figure 1 We use water in many ways. (a) We all drink water. (b) Sports, such as hockey, are played on frozen water (ice). (c) Firefi ghters use water to put out fi res. (d) Farmers irrigate their crops with water.

(a) (b) (c) (d)

Making PredictionsPrepare for reading by making a prediction about the information you will learn about in this section.

• Scan the section for information: the title, subtitles, pictures, and margin features.

• Skim the fi rst sentences of the fi rst one or two paragraphs of the text.

What do these sentences tell you about this text? What kind of information will be described or explained on this page?

Make a prediction about the text. As you read, confi rm or change your prediction. Make new predictions about what will come next. Making predictions helps to make informational text easier to read.



10.2 What Is Water? 269NEL

The Water Particle According to the particle theory of matter, pure water is made up of many identical water particles. However, water particles are composed of two even smaller kinds of particles—oxygen and hydrogen. Each particle of water is made up of one oxygen particle and two hydrogen particles joined together (Figure 2).

States of WaterWater can exist as a solid (ice), as a liquid (water), or as a gas (water vapour). Th e particles of each state of water behave diff erently.

Solid ice has a defi nite shape. Th is is because the water particles of ice cannot move freely around each other; they can only vibrate (Figure 3(a)). In liquid water, particles vibrate faster and are free to move around each other in all directions (Figure 3(b)). In water vapour, the particles are very far apart. Th ey have lots of energy and move very quickly in all directions (Figure 3(c)).

Th ink about the temperatures at which each state of water exists. Where might you expect to fi nd each state of water on Earth?

oxygen

hydrogenhydrogenFigure 2 Water particles are made up of one oxygen particle and two hydrogen particles joined together.

1. Describe a particle of water. What other particles make up a particle of water?

2. You are given a sample of tap water that is clear, yellowish, and odourless. Is this a sample of pure water? Explain.

3. Choose one of the states of water. (a) Draw a labelled diagram to show the arrangement of

water particles in this state. (b) Describe the arrangement of water particles in this state.

CHECK YOUR LEARNING

Figure 3 Water on Earth can be found as a solid (a), a liquid (b), or a gas (c).

(a) (b) (c)

Go to Nelson ScienceGo to Nelson Science

To learn more about the structure and states of water,



10.3 The Water Cycle Water is the only substance that exists on Earth in each of its three states. Water easily changes from one state to another. Water sometimes changes its location by changing state in a continuous pattern called the water cycle. Th e water cycle is self-renewing and constant. Th e Sun provides the energy to power the water cycle.

Changes of StateWhen water changes state in the water cycle, the total number of water particles remains the same. Th e changes of state include melting, sublimation, evaporation, freezing, condensation, and deposition. All changes of state involve the transfer of energy. Figure 1 shows how the water particles in each state behave as energy is added or removed.

When solid ice gains thermal energy, it changes state from solid ice to liquid water in a process called melting. Ice cubes in a cold drink, for example, gradually melt. Each spring you see snow melt into slush and puddles.

Sometimes adding thermal energy to solid ice causes a change of state from a solid to a gas. Th is change, directly from a solid to a gas without becoming a liquid, is called sublimation. On crisp, dry winter days you might notice that snow banks shrink, or ice gradually disappears, without fi rst becoming slushy and wet.

When water absorbs enough thermal energy, it becomes a gas (water vapour). Th is process is called evaporation. Water vapour mixes with the air and seems to disappear. For example, wet clothes on a washing line dry because the water evaporates into the air.

water cycle: a continuous pattern in nature in which water moves as it changes state above, on, and below the surface of Earth

melting: the change of state from a solid to a liquid; occurs when a solid gains thermal energy

sublimation: the change of state from a solid to a gas without fi rst becoming a liquid; occurs when a solid gains thermal energy

evaporation: the change of state from a liquid to a gas; occurs when a liquid gains thermal energy

solid

sublimation

deposition

melting

gas

evaporation

releases energy (heat)requires energy (heat)

freezing condensation

decreasing thermal energy of particles

increasing thermal energy of particles

Figure 1 Energy is gained or lost whenever water changes state.

Questioning the TextTo maintain your reading focus and get more meaning from a text, ask questions as you read.

Begin by scanning the page and reading the title and headings. What questions come to mind about the water cycle?

Read the fi rst few paragraphs. Stop and refl ect on what you have read. What questions do you have? What more do you want to learn about this topic?

Move to the next paragraph and, again, stop to ask questions. The conversation in your head will help you think more deeply about your reading.



10.3 The Water Cycle 271NEL

When water vapour loses thermal energy and becomes liquid water, condensation has occurred. Rain and dew are examples of condensation. A cold can of pop placed outside on a hot summer day oft en collects water droplets. Th is is because water vapour in the air condenses when it is cooled by the cold can.

Sometimes, removing thermal energy from water vapour causes it to become a solid, rather than a liquid. Deposition occurs when water vapour changes state directly from a gas to a solid. Deposition is the reverse of sublimation. One example of deposition occurs high in the atmosphere where the temperature is very low. In these conditions, water vapour forms snow without becoming a liquid fi rst.

Liquid water can also lose thermal energy and undergo freezing: changing state from a liquid to a solid. We see many examples of this in everyday life. Puddles, ponds, lakes, and even parts of oceans freeze when the water becomes cold enough.

Changes of State in the Water CycleWater moves around Earth in the water cycle. Figure 2 shows where water is found, the state in which it exists, and how it changes from one state to another. Look at Figure 2 carefully to fi nd water in each of its three states.

condensation: the change of state from a gas to a liquid; occurs when a gas loses thermal energy

deposition: the change of state from a gas to a solid; occurs when a gas loses thermal energy

freezing: the change of state from a liquid to a solid; occurs when a liquid loses thermal energy

Sun

condensation

sublimationdeposition

precipitation

surfacerunoff

surfacewater

groundwater

freezing(water storage

in ice and snow)surface runoff

(snowmelt into streams)

cloud formation(water storage in the atmosphere)

icewater vapour

evaporation

Figure 2 The water cycle

Reading Visual Text: The Cycle MapA cycle map is used to illustrate a process that repeats itself. In nature, the water cycle and the life cycle can be illustrated using a cycle map. Can you think of other processes that are repeated in nature?




Melting, Evaporation, and Sublimation in NatureSolid water includes permanent ice and snow in glaciers and over the polar regions, and ice and snow that form in the winter. Liquid water falls to the ground in the form of rain. Liquid water also forms when winter ice and snow begin to melt. Much of this water is called runoff . Runoff water fl ows downhill under the infl uence of gravity, through streams, rivers, and lakes. Some of the water eventually reaches the oceans. All the water on the surface of Earth is called surface water.

Some liquid water seeps into the ground. Th is water, called groundwater, trickles down through openings in the soil and cracks in rocks until it hits bedrock and cannot fl ow down any farther. Th e water spreads out until it fi lls all the available spaces in the loose rock and soil above the bedrock. Th e loose rock and soil become saturated with water. Th is saturated area is called an aquifer. Th e top surface of the aquifer is the water table (Figure 3). Occasionally, natural underground caverns also fi ll up with water.

Surface water evaporates and snow and ice sublime from Earth’s surface to become water vapour. Water vapour in Earth’s atmosphere acts like a blanket that traps thermal energy close to Earth. Melting, evaporation, and sublimation are processes that occur as a result of the increasing thermal energy of water particles (Figure 4).

runoff: water from precipitation and snowmelt that fl ows over Earth’s surface

bedrock

surface water

soil

groundwater

water table

aquifer

Figure 3 Groundwater saturates loose rock and soil to the level of the water table, forming an aquifer.

Sun

sublimation

surface runoff(snowmelt into

streams)


icewater vapour

evaporation

Figure 4 Ice melts into water or sublimes to form water vapour. Liquid water evaporates when thermal energy is added.

groundwater: water that seeps through soil and cracks in rock; source of water for underground springs and wells

aquifer: a geological formation of loose rock or soil that is saturated with groundwater

water table: the depth at which loose rock and soil below Earth’s surface are saturated with water; the upper boundary of an aquifer


10.3 The Water Cycle 273NEL

Condensation, Freezing, and Deposition in NatureOnce water vapour is in the atmosphere, low temperatures cause the vapour to either condense into a liquid or undergo deposition to form ice crystals. Water droplets and ice crystals in the atmosphere form clouds. Air currents move the clouds around the planet. Th e water droplets in clouds collide to form larger droplets that fall as rain. Ice crystals fall to the ground as snowfl akes. Both rain and snow are forms of precipitation—water that falls to Earth’s surface. Fallen snow may gradually accumulate as polar ice sheets (areas of ice at the North and South Poles), icecaps (permanent ice that covers land), and glaciers (rivers of ice that slowly fl ow down mountainsides).

At low temperatures, Earth’s surface water freezes and forms solid ice. Ice is slightly less dense than liquid water. Th is explains why, in the winter, lakes and ponds develop a layer of ice that fl oats on the liquid water underneath. As a result, animals and plants can survive through the winter without being frozen solid. Condensation, deposition, and freezing are processes that occur as a result of a decrease in the thermal energy of water particles (Figure 5).

Changes with the SeasonsWinter snow melts as spring arrives. Th e snowmelt fl ows into streams and rivers, and eventually into the oceans. Some of the snowmelt sinks into the ground, becoming groundwater. As surface water evaporates to become water vapour, the water cycle is repeated.

precipitation: solid or liquid water that falls to Earth’s surface

polar ice sheet: a frozen fi eld of ice covering either the North Pole or the South Pole

icecap: a large area of ice that permanently covers land

glacier: a river of ice, formed from snow accumulated over hundreds of years, that moves slowly downhill under the force of gravity

condensation

depositionfreezing

(water storagein ice and snow)


icewater vapour

Sun

Figure 5 Water vapour condenses and liquid water freezes when thermal energy is removed.

1. Look at Figure 2. Where can you fi nd each of the three states of water?

2. Describe the water cycle. Draw your own labelled diagram.

3. Briefl y describe how solid and liquid water may be converted to water vapour.

4. Describe how water vapour changes into solid and liquid water above Earth’s surface.

5. Does all surface runoff move directly into rivers, lakes, and oceans? Explain.

CHECK YOUR LEARNING

How can you apply what you have learned about the water cycle to the Unit Task?Unit Task


To watch an animation of the water cycle,



PERFORM AN ACTIVITY10.4

Purpose To develop and carry out a plan to reduce personal water consumption, and to determine whether the plan results in signifi cant savings.

Equipment and Materialsempty 1 L container• timing device•

Reducing Personal Water Consumption If you suspect that there is far more salt water on Earth than there is fresh water, you are correct. Over 97 % of all the water on, above, and below Earth is salt water. Less than 3 % is fresh water. Most of this 3 % is frozen in glaciers and ice sheets in the polar regions. Only about 1 % of the water on Earth is liquid fresh water. Much of this 1 % lies deep below Earth’s surface.

With this information, we should consider whether we are using our scarce freshwater resources wisely. Revisit the personal water study that you conducted in Section 10.1. As a fi rst step in a personal water conservation plan, how could you reduce your personal water consumption? Here are some ideas.

Th ink about the length of time you spend in the shower. Do you • have a low-fl ow-rate shower head, or aerators on your taps? Do you leave the tap running while you brush your teeth? Consider your toilet. Check around the outside • for leaks. Could you place an object in the toilet tank to make each fl ush use less water? Do you keep the tap running to rinse the soap • from dishes when you wash them? Electric dishwashers might require the same amount of water to wash a full load as a partial load. Do you run the dishwasher only when it is full? Do you use water in the yard? If you water your • lawn, how could you use less water (Figure 1)? Which do you think uses more water: hand • washing the family vehicle or using a car wash? You might be surprised by the answer!

Questioning Hypothesizing Predicting Planning Controlling Variables

Performing Observing Analyzing Evaluating Communicating

SKILLS MENU

Figure 1 Running sprinklers longer than necessary wastes a lot of water.

empty 1 L container timing device


10.4 Perform an Activity 275NEL

Procedure1. Copy Table 1 into your notebook. Complete

column 1 with the ways in which you use water from Section 10.1.

Table 1 Tracking, Recording, and Reducing Personal Water Use

2. Plan ways to reduce the volume of water used. Base your plan on only the same water uses you listed in Section 10.1. If you add a new use of water, or if you forget to record a water use that was recorded in the previous activity, you will aff ect your comparison of total volume of water used. Write your reduction strategy for each water use in column 2.

3. As you did in Section 10.1, use your timing device to determine how much water you use for each task, but now with your reduction strategy in place. Record these values in column 3.

4. Put your plan into action for a 24 h period. In column 4, record the number of times per day you perform each task.

Analyze and Evaluate(a) Using your values in columns 3 and 4,

calculate the total estimated volume of water used per day for each task under your reduction plan.

(b) When the 24 h period is over, add the volumes in column 5 to determine the grand total.

(c) Compare your water use total in this activity with your total in Section 10.1. Did your water-reducing action plan use less water? If so, how much water did you save?

(d) How much water would you save in a week? How much water would you save in a year?

(e) Do you think you could stay with this plan for a year? Why or why not?

(f) If everyone in your household participated in your water-reducing plan, how many litres of water would you all save in a 24 h period? How many litres would you save in a year?

Apply and Extend(g) Check the population statistics for the town

or city where you live. How much water would be saved in a year if every person were able to save as much water as you did?


(h) Suggest some longer-term changes that you and your family could make to reduce your water use.

(i) Estimate or measure how much water drips from a leaky tap in 5 min. Calculate how much water would drip from the tap in a year. Find out the cost of water in your area. How much money would be saved each year by fi xing a leaky tap?


2.B.7.2.B.7.SKILLS HANDBOOK

3.I.3.I.SKILLS HANDBOOK

Ways in whichyou use water

brushing teeth

Reductionstrategy

turn off tapwhile brushingteeth 21

Actual wateruse in 24 h (L)

1 2Estimated volumeper single use (L)

3 4 5

2

GRAND TOTAL

Number oftimes per day

Which parts of this activity will be useful as you complete the Unit Task?Unit Task



10.5 Making Water DrinkableIn Canada, we usually get our drinking water from wells, lakes, or rivers. Sometimes it is pumped from these sources or stored behind dams in reservoirs. However, in nature, water oft en contains impurities and toxins. How is fresh water made safe for drinking?

The Water Treatment ProcessSources of fresh water are seldom pure enough to be used directly as drinking water because water oft en contains dissolved substances. Even water that is clear, colourless, and odourless may contain substances and organisms that make it unsafe to drink. We want to remove all potentially dangerous substances before we drink water from any source. Water treatment is the process of making water suitable for a desired end-use (such as drinking). Look at Figure 1 carefully to learn how a typical water treatment process works.

water treatment: the process of removing potentially dangerous substances from water to make it more acceptable for a desired end-use

river, lake, or reservoir

your neighbourhood

addition of chemicals

intake

coagulationandflocculation

sedimentationfiltration

disinfection

storage

Figure 1 Follow water through the treatment process to your neighbourhood.


10.5 Making Water Drinkable 277NEL

To obtain clean drinking water, the dangerous substances must be removed. Th e water treatment process follows the steps outlined below.• Th e fi rst step is to remove any large objects, such as sticks, leaves,

and garbage, from the water. A metal screen covers the end of the pipe that draws the water from its source. Th is screen blocks objects from entering the treatment plant with the water.

• Th e water enters a large tank where alum (a chemical) is added. Th e alum is stirred into the water and forms small, sticky lumps that attract most of the waste solids fl oating in the water. Th is combination of chemical and waste solids is called fl oc.

• Th e water and fl oc enter a settling tank (Figure 2). Th e water fl ows slowly to allow the fl oc to settle to the bottom of the tank.

• Th e partially cleaned water from the top of the settling tank now moves through a sand and charcoal fi lter. Th is removes any remaining waste solids and small pieces of fl oc that did not settle in the previous step. Th e water is now clear, colourless, and odourless.

• Th e water may still contain micro-organisms, such as bacteria, that can make people ill. Chlorine or ozone can be added to the water to kill these organisms. Chlorine is particularly eff ective because it remains active in water.

• Th e treated water can then be stored in sealed containers, ready for use. Th is ensures a reliable fl ow of water whenever we need it.

Other Treatment OptionsWater can be treated in several ways. Th ese methods can be used instead of, or in addition to, the steps described above.

Reverse osmosis is a technological process in which mechanical • pressure forces water through a membrane that acts like a fi ne fi lter. Th e holes in the membrane are so tiny that only water particles can pass through. All other substances are trapped and removed. Th e membrane must be properly maintained to prevent algae and other organisms from growing on it. Reverse osmosis is sometimes used to treat well water that supplies individual homes or businesses. It is rarely used as a municipal water treatment. Ultraviolet (UV) radiation eff ectively destroys • most viruses and micro-organisms, such as bacteria (Figure 3). Th is method of water treatment is sometimes used when it is especially important that the water be free of organisms and viruses, such as the water supply for a hospital. Micro-organisms can contaminate water stored in containers before it is consumed, so stored water is continuously exposed to UV radiation to prevent re-contamination.

fl oc: sticky clumps formed from the reaction of alum in water, combined with sand and other waste solids

Figure 2 These huge settling tanks at a water treatment plant allow the fl oc to sink to the bottom.

Figure 3 UV radiation is increasingly being used in water treatment. Many bottlers of spring water now use UV disinfection equipment to remove micro-organisms from water.

Sci8_UnitD_Chap10.indd 277Sci8_UnitD_Chap10.indd 277 10/24/08 12:00:11 PM10/24/08 12:00:11 PM


In nature,• water absorbs the minerals calcium and magnesium from surrounding rock. Th is makes the water “hard.” Hard water is safe to drink, but when heated it leaves mineral deposits in water pipes, hot-water heaters, and kettles (Figure 4). Adding water-soft ening chemicals removes the “hardness” from the water.

Boiling is used as an emergency measure if there is a breakdown in • the normal water treatment system. Most disease-causing organisms can be killed by boiling water for one to three minutes. Boiled water should be used within a few hours or stored in the refrigerator.

Using Water SustainablyWater treatment processes do not remove all chemicals from water. Th ere is no process at water treatment plants to remove substances such as pharmaceuticals (drugs such as antibiotics and artifi cial hormones) and oil-based liquids (motor oil and paint) from the water. It is very important that we keep these substances out of our water supply.

Only a tiny fraction of the world’s water is suitable for human use. A rising world population, along with pollution, is putting increasing pressure on this limited resource. Sustainability means working and behaving in a way that protects resources to ensure that they are available to future generations. Th e sustainability of the world’s water resources is an urgent global issue. Are we using water in a way that will make it available to future generations? Using water sustainably is everyone’s responsibility.

sustainability: being able to meet the needs of the present without compromising the ability of future generations to meet their own needs

Figure 4 Kettles and other containers that hold heated water often have limescale, which is a deposit of minerals that are insoluble in water at high temperatures.

CHECK YOUR LEARNING

1. List and describe the six main steps that water goes through in the water treatment process.

2. Is clear, colourless, and odourless drinking water always safe to drink? Explain.

3. Describe how the membrane works in the reverse osmosis process. Use a labelled diagram in your description.

4. (a) Why is it important to ensure that treated water remains safe to drink when it is stored after treatment?

(b) Describe one way to make stored water safe.

C

There are several ideas in this section that might be useful as you consider a water issue for the Unit Task. Make a list of relevant ideas.Unit Task


To learn more about using water sustainably,


CONNECT

279NEL

Backcountry Challenge

Sweat is dripping down your forehead. It is 34 °C but it feels like 44 °C. You have been hiking for hours and have now reached a clearing by the river where you are going to set up camp (Figure 1). Your throat is parched, and the clear, cool water looks refreshing, but is it safe to drink?

Your trail mate sets down his backpack and unzips it. He pulls out some of the hiking supplies that the two of you packed before leaving. First, he takes out some small iodine tablets. Adding a tablet to a mug of water will kill the micro-organisms in it and make the water safe. However, it only works for warm water, and you have cool water. He puts the tablets away. Next, he takes out a portable water fi lter that uses a carbon fi lter. This device has a hose to pour the water into the top, and then the water trickles through the carbon and into the container below (Figure 2). The micro-organisms stay behind, stuck to the carbon. Your trail mate hands a bottle to you, and you eagerly turn to the lake to fi ll it.

Your friend is holding a thin plastic pen that looks like a thermometer. He dips it into the water bottle and presses a button; you see a light fl ash (Figure 3). He has used an ultraviolet (UV) light to kill the micro-organisms in seconds. It is the latest technology in portable water treatment. You fi nish treating your water by running it through the portable water fi lter, and then you and your friend enjoy a cool drink of clean water!

Figure 1 Drinking water directly from an outdoor source can cause sickness.

Figure 2 Health Canada has surveyed hundreds of water treatment products, like this portable water fi lter.

Figure 3 UV water treatment is a fast and effi cient way for hikers to treat water.



SOLVE A TECHNOLOGICAL PROBLEM10.6

ScenarioYou are part of a tree-planting crew assigned to replant a clear-cut area in rugged northern Ontario. Th e main source of fresh water, a nearby river, is heavily polluted. You have been warned not to drink water from the river. Th e only other source of water is a stream that fl ows into this river. However, because of soil erosion from the stream banks, the water in the stream appears quite dirty.

Design BriefYou will design and build a water fi ltration device using readily available materials. You will assess the performance of prototypes of the device by testing the clarity of the fi ltered water. You will use your test results to adapt your design and construct the most eff ective fi lter possible.

Your fi lter will be assessed according to the following criteria:

Th e water fi ltration device should be • constructed from readily available materials.Th e water fi ltration device should be sturdy and • reusable.Th e fi ltered water should be clear, colourless, • and odourless.

Equipment and Materialsprovided samples of stream water• empty pop bottle with a hole cut in the bottom• collection fl ask• support stand• clamp• fi ltration materials• any other readily available material from home • that you want to use

Research and ConsiderResearch additional information on the water treatment process. Consider the available materials. Brainstorm with your group to decide on a fi lter design that might work well. Remember that modifying and improving others’ ideas is acceptable; directly copying others’ ideas is unethical and unacceptable.


A Water Filtration DeviceAbout 70 % of Earth’s surface is covered with water, but the supply of fresh water for drinking is limited. Th e water may be unavailable (frozen) or may contain contaminants that make it unsuitable for drinking. Human activities sometimes introduce contaminants into the water. Th ere are, however, simple ways of removing some contaminants from fresh water. In this activity, you will design and build a simple water fi ltration device.

provided samples of stream water

support stand

empty pop bottle with a hole cut in the bottom

clamp

collection fl ask

fi ltration materials

Identify a Problem/Need

Planning Selecting Materials and Equipment

Designing Testing Modifying Communicating

SKILLS MENU


10.6 Solve a Technological Problem 281NEL

Plan and Construct1. In your group, plan and sketch at least

three models of fi ltration devices that you think will work (Figure 1). Include labels and brainstorming ideas on the sketches. Your sketches do not have to be completely diff erent; you could include parts of other sketches when drawing a new one.

2. Choose the sketch of the prototype that you think will be most successful. Include your choice of fi ltration materials.

3. In your journal, develop a detailed procedure for building your prototype.

4. Finalize your procedure and have your teacher check it.

5. Collect the equipment and materials that you need and construct your prototype.

6. Adjust your written plan during the building process as needed. Remember to record anychanges in your notebook.

Test and ModifyTest your prototype to see whether or not it is successful. Check that you have met the criteria in the Design Brief. Experiment with diff erent fi ltration materials. Observe and record your observations each time you test your device. Continue to improve your design. Note any changes.

EvaluateCompare the performance of your best fi ltration device with the criteria in the Design Brief. Consider the following questions:

1. How well did your fi lter meet the criteria?2. What combination of materials worked best?3. What arrangement of materials worked best?4. If your fi ltered water did not meet the criteria,

look at your design and fi nd reasons for the poor performance of your fi lter.

5. Identify at least one skill that you need to improve. Discuss with your teacher how you might develop this skill.

6. If your fi lter successfully produced clear, colourless, odourless water, would you drink it? Why or why not?

Communicate(a) Review the process that you followed to solve

the problem in the Scenario. Prepare a fl ow chart to show your design process.

(b) Research a simple fl ow chart for a general design process. Compare your own fl ow chart to the simple one that you researched. How similar were the two design processes?


4.B.2., 4.C.4.B.2., 4.C.SKILLS HANDBOOK

4.B.5., 4.B.6.4.B.5., 4.B.6.SKILLS HANDBOOK

unfiltered water

pop bottle with hole cut in bottom

layers of filtration materials

filtered watercollection flask

support stand and clamp

Figure 1 A possible water fi ltration setup

Never taste or drink anything in the science classroom.

In this activity you solved the technological problem of improving water quality for drinking. How can you apply this knowledge to the Unit Task?

Unit Task


EXPLORE AN ISSUE CRITICALLY


10.7Safe Drinking Water in a First Nation Community In 2005, the media reported that the First Nation community of Kashechewan (Figure 1) was being evacuated due to fl ooding, which had led to water contamination. Th is was not the fi rst time that the community had been evacuated (Figure 2). High levels of bacteria were found in the drinking water supply, even though the water treatment plant had recently been rebuilt. Th e problem was that the intake pipe for the treatment plant was placed downstream from the community’s sewage lagoon. Tides from James Bay had pushed the dirty water back and forth across this pipe. Th e people of Kashechewan suff ered ongoing skin rashes and intestinal problems. Th ese problems were caused by drinking and using water containing dangerous micro-organisms.

The IssueIn 2003, Indian and Northern Aff airs Canada and the Assembly of First Nations attempted to address specifi c drinking water concerns. Th ey announced a Protocol for Safe Drinking Water in First Nations Communities. You have been asked to assess the eff ectiveness of the Protocol. Is it a sustainable solution to the problem of unsafe drinking water in First Nations communities?

Albany River

Kashechewan

JamesBay

Hudson Bay

W E

N

S

ONTARIO

QUÉBEC

0 75 150 km

Figure 1 Kashechewan is a small, isolated community. Most of the inhabitants are Cree.

Figure 2 Families were moved hundreds of kilometres from Kashechewan to Stratford, Sudbury, and other Ontario towns.

Defi ning the Issue Researching Identifying Alternatives Analyzing the Issue Defending a Decision Communicating Evaluating

SKILLS MENU


10.7 Explore an Issue Critically 283NEL

GoalTo decide whether there are serious concerns regarding drinking water in First Nations communities and, if there are, to assess whether a sustainable solution has been developed.

Gather Information Search media archives for reports about unsafe drinking water in First Nations communities, including Kashechewan. Consider these questions as you gather information:

How does each article capture and maintain the interest of the • reader?How is the information in each of the articles similar or diff erent? • Why do diff erent articles present diff erent positions on the issue? • What groups are quoted and referenced in the articles? • Who wrote each article? Could the author be biased in any way?• Check the Government of Canada website. Read about the “Expert

Panel” that was formed to investigate the issue in Kashechewan. Read highlights from the Protocol for Safe Drinking Water in First Nations Communities. How many of the Expert Panel’s recommendations appeared in the Protocol? Does the Protocol adequately address the drinking water concerns in First Nations communities?

Identify three or more groups whose opinions on this issue are presented by the media. Compare their points of view.


Identify SolutionsDoes the Protocol for Safe Drinking Water in First Nations Communities provide a sustainable solution to the problem of unsafe drinking water? Explain your answer and, if necessary, suggest alternative solutions. Be sure to refer back to the articles that you researched.

Make a DecisionDecide where you stand on the issue of safe drinking water in First Nations communities, and decide what steps should be taken.

Communicate Prepare to participate in a class discussion by identifying the key points that support your decision. Communicate your decision and supporting information using presentation soft ware, a photo essay, or some other presentation format.

3.3.SKILLS HANDBOOK

8.8.SKILLS HANDBOOK

Points of ViewIt is important to gather information from a variety of sources before making and defending a decision. Media reports will often take different points of view, or positions, on an issue. This helps to show the reader or viewer that there are similarities and differences in opinions among individuals and groups.



BIG Ideas

Water is crucial to life on Earth.

Water systems infl uence climate and weather patterns.

Water is an important resource that needs to be managed sustainably.


Looking Back

CHAPTER

✓

SUMMARY

✓

We use water in many different ways every day.

Water, in its pure form, is essential to life. Most of the water on • Earth is found mixed in with other substances. Water • particles are made up of one oxygen particle and two hydrogen particles. Water exists in three states: solid (ice), liquid, and gas (water vapour).Some of the uses of water are essential; others are optional.•

Safe Drinking Water

Water circulates around Earth in the water cycle.

Th e total amount of water on Earth remains constant.• Th e water cycle is a continuous pattern in nature, in which water • changes states and moves from one location to another. For example, liquid water evaporates from Earth’s surface; it later condenses and falls to the ground as precipitation.Th e Sun provides the energy to drive the water cycle.• Melting, evaporation, and sublimation are processes that involve • increasing thermal energy. Condensation, deposition, and freezing are processes that involve decreasing thermal energy.

10


VOCABULARY

water cycle, p. 270

melting, p. 270

sublimation, p. 270

evaporation, p. 270

condensation, p. 271

deposition, p. 271

freezing, p. 271

runoff, p. 272

groundwater, p. 272

aquifer, p. 272

water table, p. 272

precipitation, p. 273

polar ice sheet, p. 273

icecap, p. 273

glacier, p. 273

water treatment, p. 276

fl oc, p. 277

sustainability, p. 278

Chapter 10 Summary 285NEL

The skills of analysis can be used to determine personal water use and ways to reduce water use.

Th e amount of water used in a day can be estimated with simple • measurements and calculations.Th e ways in which water is used can be analyzed to determine how • to reduce water use. Water can be used in a sustainable manner.•

Water must be treated before it is safe to drink.

Water in nature contains many substances and micro-organisms • that can be harmful to living things.In most towns and cities, water goes through a water treatment • process.Small-scale technologies are developed to treat water that has not • been through a municipal water treatment process.Th e sustainability of water as a resource should be considered • whenever water is used.

The skills of technological problem solving can be used to design and build a simple water fi ltration device.

Research skills may be used to explore diff erent water fi ltration • devices.Technological problem-solving skills can be used to develop a • design for a water fi ltration device.Simple, everyday materials can be used to build a water fi ltration • device.

The media report on water-related issues in different ways.

Reports may take a particular perspective in an attempt to sway • the audience.Diff erent perspectives must be taken into account before forming • an opinion on an issue.



CHAPTER

REVIEW

What Do You Remember?1. Describe three characteristics of water at

room temperature. K/U

2. (a) Name the two kinds of particle that make up a water particle.

(b) How many of each kind of particle are found in a water particle? K/U

3. (a) List the three states of water. (b) Name a place in, on, or above Earth

where you would fi nd each state. K/U

4. (a) What is an aquifer?(b) Does water that collects in an aquifer

remain there forever? Explain. K/U

5. Describe the role of the Sun in the water cycle. K/U

What Do You Understand? 6. (a) Defi ne the term “sustainability” in your

own words.(b) How does your current personal water use

aff ect sustainability? K/U A

7. (a) As water evaporates from the oceans, what happens to the total amount of water on Earth? Explain.

(b) How does this aff ect living things? K/U

8. (a) Describe one characteristic of water in liquid state.

(b) Explain the characteristic of liquid water described in (a). Include a diagram that illustrates the arrangement of water particles in liquid state. K/U A

9. Draw a diagram showing the three states of water. Indicate the changes of state that water can undergo. K/U C

10. Explain how condensation and precipitation are similar and diff erent. K/U

11. Create a fl ow chart showing the treatment of municipal drinking water. K/U C

12. Ice forms on the surface of a body of water in winter. Explain why the ice does not sink to the bottom (Figure 1). K/U

13. You dip a container into a small lake in northern Ontario. Th e water is colourless and has no odour. Would it be safe to drink? Explain. K/U

14. Not every Canadian has access to treated drinking water. (a) Where might household tap water not

go through a municipal water treatment process?

(b) If freshwater resources are to be used sustainably, which of the following do you think will have the greatest impact: building more water treatment plants, using less water, or cleaning wastewater before returning it to the ecosystem? Explain your answer. T/I A

Solve a Problem!15. You discover a slow drip underneath the

toilet tank. (a) Research two reasons why the water is

dripping. (b) How could you discover the volume of

water that dripped in 24 h? T/I A


10

Figure 1

K/U Knowledge/Understanding T/I Thinking/InvestigationC Communication A Application

The following icons indicate the Achievement Chart categories:


Chapter 10 Review 287NEL

16. You are visiting friends at a cottage. You learn that the drinking water for the cottage is pumped directly from a well on the property into the cottage water pipes. (a) Research how water from a private well

is typically treated to make it safe for drinking.

(b) Compare this “private well” process with the municipal water treatment process. You can use diagrams or fl ow charts in your comparison. T/I C A


Create and Evaluate!17. Read the following newspaper story:

(a) Identify the two problems that appear to be linked to the drinking water.

(b) Can you conclude, from the information in the story, that the company has no responsibility for the problems identifi ed in (a)? Explain.

(c) What has the Federal government done to solve the problems?

(d) What questions do you still have aft er reading the newspaper story?

(e) Would you consider this to be an objective report? Why or why not? T/I A


18. Create a poster or short cartoon strip to encourage others to reduce the volume of water that they use. T/I C

19. Some municipalities draw water from wells to supply homes and businesses in the town. Groundwater is usually cleaner than surface water. Research the treatment that municipal well water goes through to make it safe for drinking. Present your fi ndings as a poster or fl ow chart. T/I C

20. A water particle landed on a glacier thousands of years ago. Th e water particle became part of the ice. As Earth’s climate warmed, the water particle was released from the ice. Write a story, draw a cartoon, or create an animated movie about what happened next to the water particle. K/U C

Refl ect on Your Learning21. In this chapter you attempted to use less

water in a 24 h period. (a) How successful were you in your attempt?(b) Did you fi nd it easy or diffi cult to reduce

your water use? Why?(c) What did you learn during this process?

22. Th ink back to the Key Question on the fi rst page of this chapter.(a) In a brief paragraph, answer the Key

Question. You may use diagrams.(b) Write one or two more questions about

the topic of this unit that you would like to explore.

Drinking Water Problems PersistA small First Nations community on the Black River continues to suffer skin rashes and diarrhea, particularly among children and the elderly. The community is located downstream from the ONPulp, a local pulp and paper mill. ONPulp has spent millions of dollars to ensure that its wastewater is treated on site before being released back into the Black River. In addition, the Federal Department of Indian Affairs has recently built a water treatment plant for the community, along with a new school and community centre.

To do a self-quiz Go to Nelson Science


unit water systems d - chalkdust: mr. caruso grade 8 · sci8_unitd_chap10.indd 258 10/24/08...

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