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Slide2: 

oxygen hydrogen positive negative substance molecule dissolve 分子 溶解 物质 氧气 氢气 正的,积极的 负的,消极的 Match words and meanings:

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Match words and meanings: 密度 热容量 质量 海洋运动 体积 盐度 heat capacity ocean motion salinity mass volume density

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Listen to the tape and try to match the main ideas of each part, then do true or false exercises.

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E. water makes the ocean a great place to live. A. Marine animals and plants take advantage of the density of water. C. The heat capacity of water keeps the temperature of the ocean steady, making it a safe and comfortable habitat. F. Ocean motion adds energy to the marine ecosystems and moves nutrients around. D. The salinity of sea water affects its ……. 1._____ 2._____ 3._____ 4.____ 5._____ 6._____ B. The chemical structure of water…… E B D A C F

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True or false 1 There are about five billion species in the oceans ranging from the tiniest plankton to giants like sharks and whales. ( ) 2 The water molecule is made of two hydrogen atoms and one oxygen atom. ( ) F F million made up of

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3 Pure water has a higher freezing point and is lighter than salt water. ( ) 4 If a substance has a density 888kg/ m3, it will float on Water. ( ) 5 The heat capacity of water is relatively high, so that most animals don’t like living in it . ( ) 6 The most important thing we can learn about water, is that we must protect it and use it wisely. ( ) T T F T

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1.Where did life begin? 2.How many species of life are there on earth? 3. What are some examples of life in the ocean? In the deep blue seas. About 5 million. Plankton, sharks and whales.

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1.What makes water an excellent medium for life? 2.What is the chemical structure of water? 3. What are different parts of the structure? 4. How does its chemicals structure work? 5. What is water?

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1.What makes water an excellent medium for life? 2.What is the chemical structure of water? 3. What are different parts of the structure? Its chemical structure. 2 hydrogen atoms and 1 oxygen atom. Positive end, negative end

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4. How does its chemicals structure work? 5. What is water? Water is a liquid at room temperature with a relatively high freezing point. It causes water to dissolve (break down) both solids and gases.

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What is sea water? What gives sea water its main properties? How does salinity work? Dissolved gases and solids mixed with pure water. The pure water. It affects water’s weight and freezing point.

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1.What is density? 2.What is the density of pure water? 3.How can sea life float? The relationship between mass and volume. 1,000 kg/m3 By taking advantage of the density of water.

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4.Why don’t the oceans freeze totally? Because the density of water decreases when it freezes.

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1.What is heat capacity? 2.Why can the oceans keep temperature steady?

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1.What is heat capacity? 2.Why can the oceans keep temperature steady? the amount of energy it takes to raise the temperature of a substance by one degree centigrade Water can absorb and give off much heat without big changes in temperature.

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1. How does sea water move? Dense water sinks and less dense water is pushed to the surface. 2.Which is the most valuable among natural resources? 3.What can we learn about water from the passage? water We must protect it and use it wisely. Our future depends on it.

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Fill in the blanks Seen from the space, the earth is an ______ planet. Water is very important to life. It is said that life on the planet began in the ______. Marine life is _________ rich. Life in the oceans _________ from the tiniest ___ ____ ___up to giants like _____and ____ . The water molecule ___ _____ ____ ___ 2 hydrogen atoms and 1 oxygen atom. Water exists in three states. It has a relatively high __________ point. ocean oceans incredibly ranges all the way sharks whales is made up of freezing

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Salt water has a ________ freezing point and is ________ than fresh water. There are many _____ of marine life. There is life even on the ________ of the deepest oceans. The creatures on the ocean floor manage to survive without ________ and get _________ from other sources lower heavier species bottom sunlight energy Species bottom sunlight energy lower heavier

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What are the properties of water? Water is polar. Water is liquid at room temperature. Water has a relatively high freezing point. Water has density 1,000 kg/m3. Water has high heat capacity. …

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Where there is water, there is life!

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As we know water is limited, we should protect it. But how can we protect it? How can we use it wisely?

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1.Don’t disturb the wild life in oceans. 2.Don’t throw trash(废弃物) on the water. 3.Don’t pour waste water into river and soil pay more attention to it . 4.Don’t mix water with some poisonous things. 5. …….. We should :

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Homework : Write a short writing about how to protect water. Read the passage again and again.

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