Read p.4 Activity. Class Discussion (The many ways people use water) P. 5. Read p.6 Read pp. 8-9

Transcription

1 Grade 8 Science

2 Read p.4 Activity Class Discussion (The many ways people use water) P. 5 Read p.6 Read pp. 8-9

3 Water exists everywhere on Earth, and covers 70% of its surface. 97% of this water is found in the oceans. Another 2% is ice and snow, leaving only 1% as fresh water found in the ground, rivers, lakes and streams. Finding fresh water to drink is a challenge in many places, as most fresh water is under the ground.

4 How can we do it? Class discussion on how to do a model of the various changes of state.

5 Earth is the only planet with water in all 3 states Water is continually cycling through the water cycle Solid Liquid Gas Liquid Solid Gas Liquid = Melting Gas = Evaporation Liquid = Condensation Solid = Solidify/Freeze Gas = Sublimation Solid = Deposition Heat energy from the Sun causes these changes to drive the water cycle.

6 The water cycle occurs everywhere, not just oceans Water evaporates when it is warmed, and then condenses in the atmosphere as clouds when it cools and falls as precipitation. The water then runs-off back to storage basins, or soaks into the ground. A hydrologist is a scientist who studies water systems An oceanographer studies oceans specifically Bill Nye Music Video: Water Cycle

7 P. 13 Questions 1-8 in your notebook FOLDABLE ACTIVITY p.7

8 The atmosphere is the environment surrounding the planet. The lithosphere is the solid rocky ground of the Earth s crust. The hydrosphere is all of the water on Earth, in the ground, in the air, in the oceans anywhere from the bottom of the sea to the sky. In other words, water belonging to the hydrosphere can be found in both the lithosphere and the atmosphere.

9 Wild, Weird, Wonderful PENGUINS! MSB: Water Cycle

10 Read p. 14 and p. 16 (c) McGraw Hill Ryerson 2007

11 Ocean water s salinity = 200X greater than fresh water Average salinity of oceans is 35 parts per thousand Oceans at equator (evaporation) and poles (ice) have the highest salinity (removing water increases salinity) Ocean locations near rivers have low salinity, due to addition of fresh water from the World Ocean Atlas 2001 Take the Section 10.1 Quiz

12 Salt water is composed of minerals dissolved during runoffs occurring over millions of years Volcanic eruptions also release minerals from inside Earth Sodium ions (Na + ) and chloride ions (Cl - ) are most common solids in ocean water Na + ions and Cl - ions > 75% of all solids in ocean water Mixed and joined in the ocean, NaCl is chemical Formula for salt

13 Density of ocean water (kg / m 3 ) = Volume (m 3 ) Density = how tightly packed the molecules are in an object Less dense always floats on more dense Eg. warm air rises above cool air, and oil floats on water We float better in salt water than fresh water Mass (kg) Bill Nye: Ocean Currents See page 371 (c) McGraw Hill Ryerson 2007

14 Salt water has slightly different properties than fresh water Salt water freezes at 1.9 ºC (c) McGraw Hill Ryerson 2007

15 Do Reading Check Questions 1-5, p. 17 (c) McGraw Hill Ryerson 2007

16 How to do a proper lab write-up for Science 8! Lab Safety Video Part 1 Lab Safety Video Part 2 Lab safety FSU Safety Violations Title Your name Group names (if any) Date: Purpose: Write it from text - word for word! Materials: Write it from text - word for word! Methods: Write See p. Data: This is where you write your observations, draw tables, graphs, etc. Analysis: You should write out the questions assigned and leave space for the answers. Other information... Written on loose leaf and goes in your science binder or duotang. We do usually do a pre-lab write up BEFORE we do the lab, and you are NOT allowed to do the lab until the pre-lab is done. You will get credit for doing the pre-lab write up.

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19 Conclusion: Were your predictions correct? What have you learned?

20 ACTIVITY 1-3A (c) McGraw Hill Ryerson 2007

21 Read Career Connect! Page 20 (c) McGraw Hill Ryerson 2007

22 ACTIVITY 1-3B Do questions 1-4 (c) McGraw Hill Ryerson 2007

23 Check your understanding questions1-10, p.21 Do Pause and Reflect in your notebook, p. 21 (c) McGraw Hill Ryerson 2007

24 QUIZ!!! (c) McGraw Hill Ryerson 2007

25 Precipitation becomes run-off as gravity pulls water down into the groundwater, a lake or an ocean basin. Run-off increases if: precipitation falls on rock, as soils allow water to soak in heavy rainfall saturates the ground so water can t soak in long periods of rainfall saturate the ground so water can t soak in water can flow quickly down a steep slope, not having time to soak in there is no vegetation, as plants help to absorb water and hold soil with their root systems there is human development and no soils Human development often alters run-off (c) McGraw Hill Ryerson 2007

26 Read pp

27 Drainage basins are large areas where surface water all moves towards one main river Run-off flows into streams and smaller rivers, which are tributaries of large rivers, forming a branching system Large rivers are separated by very high ground called divides The Rocky Mountains form the Continental Divide, which divides BC and Alberta See page 379 (c) McGraw Hill Ryerson 2007

28 Ground water is water that soaks into the ground Rock/ground with good porosity allows more water to enter More pores (spaces in the rock/soil), the better the porosity An aquifer is a layer of porous rock that allows ground water to flow, almost like a river below the surface. Humans get fresh water from Reservoirs, natural or man-made Wells, drilled into aquifers down to the water table, which is the top level of the zone of saturation. The water table is very deep in deserts, but near the surface in swamps The water table rises during wet seasons See page 380 (c) McGraw Hill Ryerson 2007

29 Almost 66% of all fresh water on Earth is in glaciers Glaciers form from layers of snow falling over many years Glaciers melt slowly under their own weight, and slowly flow downhill Glaciers cover about 10% of the Earth s surface Alpine glaciers (aka valley) found in mountains Continental glaciers (aka ice sheets) cover huge areas of land. Eg. Greenland and Antarctia Glaciers flow until they reach an ocean, where crevasses open and icebergs fall off reach an area where warm temps allow as much melting as re-freezing, or recede if they melt faster than they can freeze (c) McGraw Hill Ryerson 2007

30 97% of the Earth s water is salt water Most of the Earth s fresh water is found in ice and snow (e.g. glaciers). Less than one-third of the Earth s fresh water is available for human use because most of it is frozen and a lot of it is found underground. For water to change from one state to another there has to be a change in temperature. See diagram on page 9.

31 Solid Glaciers Liquid Oceans, rivers, lakes, ponds, streams, etc. Gas Clouds, around underwater volcanoes, geysers Evaporation Condensation Condensation Evaporation Water that is polluted in one place may evaporate into clouds and be pushed by the wind to other places. In this way, the pollution can spread from one place to another.

32 1. Salinity is the amount of salt dissolved in a specific amount of water 2. Ocean water is saltier near the equator because there are higher rates of evaporation near the equator. When the water in the ocean transforms into vapour in the air, it leaves the salt behind

33 3. Ocean salt can come from: a) Water moving over and through the ground picks up materials from the rocks. They get carried by the water from the land and into the ocean. b) Undersea volcanic eruptions from the sea floor release large amounts of sulphur, fluorine, chlorine, and hydrogen into ocean water. Eruptions on land spew similar materials high into the atmosphere. These materials then fall directly into the ocean, or onto Earth s surface from where they get carried to the ocean as runoff.

34 4. Density is the amount of mass of a substance in a certain unit volume. 5. Ocean water is denser than fresh water because there is more salt in the ocean.

35 1. Ocean water and fresh water differ in several ways. The main one is in their salinities. Ocean water is more than 200X saltier than fresh water. 2.Dissolved chlorine occurs in the greatest amounts in ocean water (55%). See Figure 1.7 on page Ocean water is salty even though fresh water from the land eventually makes its way there because the fresh water moves over and through the ground. In doing this, it picks up materials from the rocks. These materials are the salts found in the ocean.

36 5. a) Ocean water. b) Ocean water is denser than fresh water because is has more salt in it. 6. Adding salt to fresh water lowers the freezing point (the freezing point of fresh water is 0 o C, the freezing point of ocean water is -1.9 o c). 7. People do not try to mine valuable minerals out of ocean water because they occur in extremely small amounts (see description under figure 1.7, p. 16)

37 8. To separate dissolved salts from ocean water I would boil it. The salts would remain in the pot and the water would become water vapour in the air. 9. Oceans in tropical areas have higher salinities because the temperature around these areas is warmer than in other places on Earth. This means that there is more evaporation, which leaves the salts behind in the ocean while the ocean water becomes water vapour. 10. Water is very salty around the North and South Poles because when the water freezes and changes into ice, it leaves the salt behind.

38 1. A drainage basin is an area of land that drains into a body of water, such as a river, pond, lake or ocean. The area of land within a drainage basin can be large or small. 2. The Continental Divide is the Rocky Mountains. They separate the Pacific drainage basin (in B.C.) from drainage basins to the east of the Rocky Mountains (in Alberta). 3. Run-off is water that does not soak into the ground or evaporate but instead flows over the Earth s surface.

39 Gravity is the force that pulls water to the lowest point. The following factors affect run-off: The nature of the ground material soil absorbs water better than rock, so a rockier ground would create more run-off. The amount of rain more rain means the ground can t absorb water as quickly, so there will be more run-off. The length of time it rains If it rains for long periods of time the same will happen as if we get a lot at once.

40 The slope of the land the steeper the land is, the faster water will flow downhill. When water moves too quickly it can t be absorbed by the soil as well. The amount of vegetation grass, trees and shrubs absorb water along with the soil, so more vegetation means less run-off. The amount of development in an area when there is a lot of pavement or concrete, water is usually channeled into storm sewers. This means there will be a lot more run-off.

41 1. When snow doesn t melt it begins piling up. As it accumulates, the weight of the snow becomes great enough to compress the bottom layers into ice. Eventually, the snow can pile so high that the pressure no the ice on the bottom causes partial melting. Then, the ice and snow begin to slide downhill. This moving mass of ice and snow is a glacier. 2. Water would not soak into the ground when flowing down a hillside after a heavy rain because gravity is pulling the water down the hill faster than it can be absorbed by the soil.

42 3. Run-off is important to the water cycle because it allows the precipitation that falls to become part of larger bodies of water, which then evaporate, condense, and precipitate again. 4. Rain drops that fall to the ground will either soak into the soil and become part of the ground water, become part of the root systems of a plant, be drunk by an animal, or flow as run-off to a larger body of water.

43 5. A) Decrease run-off. Plants absorb more water. B) Decrease run-off. If the slope is less steep the water will have more time to be absorbed. C) Increase run-off. Concrete/pavement do not absorb water very well. 6.

44 1. A) 70% of the Earth s surface is covered in water. B) 3% of that water is fresh (2% of the fresh water is frozen, 1% is available for human use). 2. The sun supplies the energy for the water cycle. 3. A hydrologist studies water systems and helps solve problems related to controlling the quantity and quality of water.

45 4. It is so easy to float in the Dead Sea because there is so much salt. The high salinity makes the water in the dead sea much more dense than a human s body, so they can float easily on top of it. 5. A divide separates one drainage basin from another (e.g. the continental divide) 6. A) Receding means falling back. In the case of glaciers it means that they are melting back from where they were, moving closer to the poles.

46 B) If the glaciers are melting the sea level is rising. This could cause flooding and other disasters. 7. Done on whiteboard in class. 8. a) A large shopping mall would create a lot of run-off. This would make a lot of water more available in the water cycle. b) 200 families would use a lot of water. This would remove a lot of water from the water cycle. c) Logging would remove a lot of trees from an area, meaning there would be a lot more run-off. This would again make more water available to the water cycle.

47 9. I think the banks should be covered in trees. This would decrease the amount of run-off on the road, making driving conditions safer. Hydroplaning can happen when there is a lot of water on the road. 10. Controlling the amount of run-off in an area is very important. Run-off is essential for filling the lakes, streams, and rivers that in turn help to keep the oceans filled with water. However, if there is too much run-off this can cause flooding.

48 11. a) Town A is more likely to have a shortage of water in the summer. This is because town A s demand for water exceeds their supply from April until October. In the summer their demand for water is the greatest, but their supply is a lot lower. b) The demand for water in both towns is lowest in January and December. c) The water supply for both towns begins to drop in the spring. I think this is because people use more water in the spring on their lawns, in pools, and to keep cool.

49 12. The government must try to keep groundwater safe because pollution in another place could be connected to the ground water through the tributary systems leading to a drainage basin. Because we cannot see where the groundwater reservoirs meet up with other areas in a drainage basin, there is a chance that they could become polluted and cause harm to people, animals and the environment if they were not monitored. They government needs to watch out for pollution, bacteria, and other ways that can contaminate ground water.