Grade 8 Science - Water Systems Notes PDF

Grade 8 Science Unit 1 – Water Systems Chapter 1 Notes The Distribution of Earth’s Water - 97% of Earth’s water is salt water - 2% of Earth’s water is fresh water that is frozen o Ex: Glaciers, Polar Ice Caps, Iceberg...

Grade 8 Science Unit 1 – Water Systems Chapter 1 Notes The Distribution of Earth’s Water - 97% of Earth’s water is salt water - 2% of Earth’s water is fresh water that is frozen o Ex: Glaciers, Polar Ice Caps, Icebergs - 1% is fresh water that is available to use o Ex: Water for 6 billion humans and hundreds of billions of other organisms The Water Cycle Lithosphere  The solid rock of Earth’s crust Atmosphere  The environment surrounding the planet Hydrosphere  all the water on Earth The Water Cycle  Water moves from Earth to the atmosphere and back to Earth again in the endless water cycle. Definitions: A - Evaporation  the change of state from a liquid to a gas. B - Condensation  the change of state from a gas to a liquid C - Precipitation  water falling to the Earth in the form of rain, hail, snow, etc. D - Groundwater  water stored in the ground (this is the layer of water people drill down into to make wells) E - Run-off  water that does not soak into the ground or evaporate but instead flows across Earth’s surface. 1|Chapter 1- Sci8 Ocean Water Vs. Fresh Water 3 major differences: 1. Salinity  the amount of dissolved salt in a specific amount of water. Ex: Ocean – about 35 g/L Fresh – about 0 g/L 2. Density  the amount of mass of a substance in a certain unit of volume. Ex: Ocean – 1.027 g/L Fresh – 1.000 g/L 3. Freezing Point  the temperature at which a liquid freezes Ex: Ocean – (-1.9ºC) Fresh – (0º) Factors affecting marine life and life in freshwater ecosystems: 1. Temperatures – organisms have a range of tolerance and can tolerate certain temperatures. 2. Dissolved Oxygen – should be around 5 mg/L or more. All organisms need oxygen to survive. 3. Phosphates – less than 10 micrograms/L. Natural phosphates are good because they help to promote aquatic plant growth and plankton. Too much phosphates however (from pollution, etc.) are bad as it can lead to an overgrowth of plant life which prevents oxygen from being dissolved into the water. This in turn, harms the fish and other aquatic life. 4. Increased Acidity – should be in the range of 5 to 8.5 5. Turbidity – the cloudiness of the water, may be due to pollution or dissolved solids. 6. Pollution – pollution is very bad for organisms 7. Upwelling (marine)– the vertical motion of water in the ocean, whereby deep, dense, cooler water moves toward the surface of the ocean. - the upwelled water contains and abundance of nutrients which support plant life near the surface. - these plants, in turn attract animal life. Upwelling is an important mechanism for producing nutrient-rich ocean water. 2|Chapter 1- Sci8 Sources of Fresh Water 1. Lakes, Ponds, Wetlands, Streams and Rivers 2. Ground Water - Water that has seeped into the soil and trickles downward through connected pores and cracks. - When the water hits the bedrock (which has no pores) it cannot sink anymore. It begins to fill the pores in the soil that it sank down through to reach the bedrock. - It is this layer that people will drill down into to make wells and pump the water up to the surface. 3. Glaciers - A moving wall of ice and snow. - When snow piles really high on the ground, the weight of it causes the bottom layers to turn to ice. - The pressure on the bottom layers forces the snow to melt and the top layers begin to slide. Iceberg  A chunk of ice that has broken off a glacier that was connected to the ocean. It can float in the ocean for a long time. Ice Ages - A period in time where the Earth has major cooling and much of the land is covered in glaciers and ice. - The most recent ice age began about 120 000 years ago and ended only 11 000 years ago. - Glaciers covered all of Canada. Glaciers and Global Warming - In the last 100 years, the average surface temperature on Earth has increased 0.5 degrees C. - Most glaciers in the world today are receding (melting or shrinking) and this is due to global warming. - - shrinking glaciers may cause rivers and oceans to rise, causing flooding in some communities. 4. Drainage Basins (Watershed) - the area of land that drains into a body of water, such as a river, pond, lake or ocean. - every stream is part of a large drainage basin. - basins are separated by areas of very high ground called Divides. 3|Chapter 1- Sci8