Grade Eight Science Water in Your Life Water It is something that we often take for granted How many things do you do each day that require water Sometimes we are not very careful about our water use ID: 394452
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Water Systems
Grade Eight ScienceSlide2
Water in Your Life
Water . It is something that we often take for granted. How many things do you do each day that require water? Sometimes we are not very careful about our water use.
Make a list of all the times you’ve encountered or used water today. Now sort the list into two categories, Essential use and Non-essential use.
What could you do to replace some of the activities that are Non-essential uses of water?
How do you use water in your daily routine??Slide3
Essential Uses
Non-Essential UsesSlide4
Where does water come from??Slide5
Water Distribution
About 71% of the Earth’s surface is covered in water.
Most of this is salt water in the oceans. Salt water makes up 97% of the water on the Earth’s surface.
How is water distributed on the Earth’s surface
?Slide6
Water Distribution
Only 3% of the Earth’s water is fresh water.
Most of the fresh water on the Earth’s surface is in a solid form. Ice sheets and glaciers make up about 69% of the fresh water on Earth.
The majority of fresh liquid water is found as groundwater below the Earth’s surface. It makes up about 30% of Earth’s fresh water.Only about 1% of the Earth’s fresh water is actually liquid water which is found in rivers, lakes, ponds, and in the soil and atmosphere.Slide7
Water Distribution
Water Distribution
videoSlide8
The Water Cycle
The water that is on the Earth’s surface today has been here for millions and millions of years.
The water cycle continuously moves water around the Earth and recycles it. The glass of water you drink today may
contain some water that was used by the dinosaurs!!!Round and Round it Goes!!Slide9
The Water Cycle
Hydrologic CycleSlide10
Water in Our World
The Earth’s oceans contain salt water. The salinity, or average concentration of salt, is about 3.5%. In one litre of water there would be about 35 grams of salt.
Salt water can also be found in some swamps, marshes, lakes and estuaries.
Salt WaterSlide11
Salt Water Around the World
The salinity of the oceans is different depending on location. Near the equator, water is saltier because of high rates of evaporation. Water molecules evaporate leaving the salt behind.The water is also saltier at the North and South poles because when the water freezes the salt is left in the liquid water.
Near the continents (land), the water is usually less salty because the fresh water from rivers empties into the ocean and dilutes the salt water.Slide12
Where does salt come from?
Some of the salt in the oceans comes from underground. As the water runs along underground, it picks up materials called dissolved solids. Volcanoes and underwater volcanoes also add chemicals such as sulphur, fluorine, chlorine and hydrogen to the ocean water.
The most common chemical added to the oceans is sodium chloride, which is the chemical name for salt.Slide13
Water in Our World
Fresh water is water that contains low concentrations of salt. Be careful though. The word fresh does not necessarily mean that the water is alright to drink. Most fresh water contains dissolved chemicals and living organisms that could make you very sick if you drank it.
Water that is safe to drink is called “potable” water.
Fresh WaterSlide14
Fresh Water AvailabilitySlide15
Density of Salt Water vs. Fresh Water
Density is the amount of mass of a substance in a certain unit volume. Salt water is more dense than fresh water. Ocean water has a density of 1027 kg/L. Fresh water has a density of 1000kg/L.
It is much easier to float in salt water than in fresh water. The higher density of salt water helps to hold the weight of your body up.
The Dead Sea is 9 times saltier than ocean water. This makes it very easy to float in it. Slide16
Freezing Points of Salt Water and Fresh Water
Both salt and fresh water have a freezing point. The freezing point of a liquid is the temperature at which it freezes, changing state from a liquid to a solid.
The freezing point of fresh water is 0 degrees Celsius.The dissolved salt in the ocean water causes it to have a different freezing point. Salt water freezes at – 1.9 degrees Celsius .Slide17
Salt Water vs. Fresh Water
Draw a Venn diagram to compare and contrast salt water and fresh water.Slide18
Questions
What is salinity?Why is the ocean saltier near the equator?
Name two sources of ocean salt.What is density?Why is ocean water more dense than fresh water?Slide19
Sources of Fresh Water
Liquid fresh water that we can use comes from the following sources:Lakes and Ponds
Rivers and StreamsWetlandsGroundwaterSlide20
Lakes and Ponds
Lakes and ponds are both basins in the ground that filled with water. There is little difference between them. Lakes do tend to be a little it larger and deeper.
Ben’s Lake
Macdonald’s pond
McClure’s PondSlide21
Lake Formation
Lakes are formed when water collects in low lying areas . They are bodies of water trapped in a basin.Slide22
Lake Formation
A lake basin can be formed in several different ways:
A) Craters or basins form at the top of volcanoes as the lava cools. Water collects in these craters and a volcanic lake is formed.
Lake FormationSlide23
Lake Formation
B) Glaciers moving along the Earth’s surface created many basins. As the ice melted, the basins were filled with melt water and lakes were formed.Slide24
Lake Formation
C) Lakes can be formed when a river is blocked by a dam. These dams may be natural or man made. Slide25
Land Locked Lakes
Some lakes are “land locked” . This means that there are no rivers leading into the lake and no rivers leading out of it. Sometimes, these lakes can be even saltier than the ocean because ground water dissolves
salts and minerals from the soil and rocks and carries it into the lake. As the water evaporates from the lake, it leaves behind the salts and minerals and the lake becomes very salty.Slide26
Wetlands
Wetlands are exactly what they say they are: areas of very wet land!
Marshes, swamps and bogs are all types of wetlands. They are all very important because they clean and filter the water on the Earth’s surface and they help to moderate water levels in times of floods and droughts.Slide27
Wetlands
Wetlands have three very important jobs to do:Clean and filter water
Control water levels during times of flooding
Provide a home to many species of plants and animalsSlide28
Rivers
Rivers begin in highlands from springs or small streams of glacier melt water. The water is pulled downward by the force of gravity.Slide29
Rivers
Many small rivers or streams join larger rivers adding more water to the river. These smaller feeders are called tributaries. Slide30
Rivers
Young fast flowing rivers carve out steep banks. Older rivers are surrounded by gently sloping land called flood plains.Slide31
Groundwater and the Water Table
Precipitation that falls onto the Earth’s surface will be absorbed into the ground. It will continue to move downward until it reaches a layer of rock which it cannot pass through. The water will build up until the soil becomes saturated. The top layer of this saturated zone is called the water table.
We drill wells into this saturated zone in order to get our water supply.Slide32
The Water TableSlide33
The Water Table
The amount of water stored underground changes through the seasons. As winter and spring rains soak into the ground, stored groundwater increases and the water table rises. When the rains stop, the water table falls as groundwater leaks into streams and the ocean. Well pumping also removes water and lowers the water table. Excessive pumping of groundwater can result in long-term depletion of
groundwater storage.
ge.Slide34
Glaciers
A glacier is a mass of ice and snow that has built up over thousands of years. There are two different types of glaciers.
Rivers of IceSlide35
Glaciers
An Alpine glacier is a glacier that is found in the high altitudes of the mountains.
Rivers of IceSlide36
Glaciers
A Continental glacier is a glacier that is found on the lands near the Earth’s poles.
There are two major continental glaciers. One continental glacier covers Antarctica and the other covers most of the island of Greenland. It covers 1.8 million square kilometres and is 2700 metres
thick.
Rivers of IceSlide37Slide38
Glaciers
The cold air flowing off the continental glaciers cool the surrounding area. These winds are called “polar easterlies”. Because the air is so cold, there is very little precipitation over the glaciers. Antarctica is actually considered a desert. It has the harshest conditions on Earth. The average temperature is -50 degrees
celsius and there is only about 3 cm of precipitation each year.
and there is only 3 cm of precipitation per year.
Rivers of IceSlide39
Glaciers
The large sheet of ice that covers the Arctic ocean is not a true glacier. Because it actually covers water, it is called a polar ice cap.
Rivers of IceSlide40
Glaciers
Glaciers store huge amounts of fresh water in the form of ice and snow. Some of the ice at the edges of the glaciers melts and rejoins the water cycle as a source of liquid water. When the pieces break away from the glaciers, they form icebergs in the oceans.
Rivers of IceSlide41
Glaciers
Icebergs can be very dangerous to ships because most of the ice is under the water and is not easily seen.
Rivers of IceSlide42
Glaciers
One benefit of icebergs is that they are composed of fresh water and could possibly be used as a source of drinking water. People may start towing icebergs to places where drinking water is needed.
Rivers of IceSlide43
Global Warming and Glaciers
Global warming is having an effect on the world’s glaciers. Warmer temperatures are causing the ice to melt more quickly. People are concerned that if the glaciers and polar icecaps melt too quickly, coastal lands may be covered with water as the sea level
rises, and rivers in the mountains may flood or dry up completely if the glacier melts altogether.
Rivers of IceSlide44
Glaciers
1. What is a glacier?
2. Describe the size and thickness of the glacier that covers the island of Greenland.3. What are “polar easterlies”?4. Describe the conditions in Antarctica that make it a desert.
5. Explain why the large sheet of ice on the Arctic Ocean is not a galcier.6. Name one benefit that icebergs might provide and one problem they may cause.7. Explain how global warming may affect glaciers and the world in the future.Slide45
Watersheds
A watershed is an area , surrounded by high land, in which all water runs to a common destination. It is sometimes called a drainage basin. Watersheds have been created over millions of years as the Earth’s surface has changed with the movement of the plates of the Earth’s crust. In Canada there are many, many watersheds. All Canadian waters will eventually flow into one of three oceans: the Atlantic, the Pacific, or the Arctic.Slide46Slide47
Canada’s Drainage BasinsSlide48
Runoff
Runoff is water that flows across the surface of the Earth. It does not evaporate or soak into the ground.Gravity pulls this water down to the lowest point. Runoff will flow along the ground until it hits a low point on the surface or finds its way into a stream.Slide49
Factors Affecting Runoff
The amount of runoff in an area is affected by the following:The type of ground material
The amount of rainThe length of time it rains
The slope of the landThe amount of vegetationThe amount of development in the area