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Answer the following questions. Work in groups of four.§ Is life on Earth possible without water? Why? § What are the main characteristics of water? § Where does water occur? § What is the composition of water? § What is hydrogen? § What is oxygen? § How does water change with temperature? § What is evaporation? 2. Read the text «What is Water» and find out whose ideas were closest to the facts. What is Water? When scientists wonder whether there is life on other planets, they often ask this question: "Is there water there?" Life as we know it would be impossible without water.
Water is a tasteless, odorless, colorless compound that makes up a large proportion of all living things. It occurs everywhere in the soil, and exists in varying amounts in the air.
Living things can digest and absorb foods only when these foods are dissolved in water. Living tissue consists chiefly of water. What is water made of? It is a simple compound of two gases: hydrogen, a very light gas; and oxygen, a heavier, active gas.
When hydrogen is burned in oxygen, water is formed. But water does not resemble either of the elements which compose it. It has a set of properties all its own.
Water, like most other matter, exists in three states: a liquid state, which is the common form; a solid, called "ice"; and a gas, called "water vapor". In which one of these forms water shall exist depends ordinarily on the temperature.
At 0 degrees centigrade, or 32 degrees Fahrenheit, water changes from the liquid to the solid state, or freezes. At 100 degrees centigrade, or 212 degrees Fahrenheit, it changes from the liquid to the gaseous state. This change from liquid, visible water to the invisible water gas is called "evaporation".
Thus, if a piece of ice is brought into a warm room, it starts to become liquid or melt. If the room is warm enough, the little puddle of water formed from the melting ice finally disappears. The liquid is changed into water vapor. When water is cooled, it expands just before it reaches the freezing point.
Water as it occurs in nature is never pure in the true sense. It contains dissolved mineral material, dissolved gases, and living organisms. (N.G.Kitkova “What is water?” 2004, Manager) 3. Work in pairs. Here are the answers to some questions about the text. What are the questions? 1. Tasteless, odorless, colorless compound. 2. A simple compound of two gases: hydrogen and oxygen. 3. In three states. 4. At 32 degrees Fahrenheit. 5. From the liquid to the gaseous state. 6. Freezing point. 7. It contains dissolved material, dissolved gases and living organisms. 8. Evaporation. 9. If the room is warm enough. 10 Gas.
4. Work in pairs. One student reads the given statements, the other pretends that he does not hear and asks him/her to repeat. Take turns. Example: STUDENT A: When water falls from clouds it's called a rain. STUDENT B: Where did you say it falls from? or What form did you say it falls in? STUDENT A: I said it falls from clouds. or STUDENT A: I didn't. But it falls in a liquid form.
1. When water falls in small frozen crystals, it's called snow. 2. When the snow begins to melt, it's called slush. 3. If the slush freezes again and becomes hard and solid, it's called ice. 4. The combination of rain and snow is known as sleet. 5. Small round lumps that fall during a thunderstorm are called hail. 6. The water forming on the leaves and flowers is a dew in warm weather. 7. The same in cold weather is frost. 8. The water united into a liquid body which is relatively motionless may be a puddle, a pond, a lake, a sea, or even an ocean. 9. While the water moves, it may be a brook, a creek or stream, or a river. 10. When water comes out of the tap, it is just plain water.
5. 9 Listen to the text about water and decide if you would agree with the following statements. Write “Yes” or “No” in the box next to each statement and be ready to explain your answers.
1. Water is the most abundant substance on the Earth._____ 2. We can not change one form of water into another by simply changing the conditions.____ 3. The three forms of water are all the same chemical substances. ___ 4. A change of state involves making new substances.____ 5. Water can be decomposed into its elements by electrolysis.___ 6. Water vapour is usually defined as steam._____ 7. Water’s chemical symbol is H2O.___ 8. Water can be synthesized by burning hydrogen in the air.___
Date: 2016-01-14; view: 1447
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