Unit 2 Topic 2 Section C教案.doc

Unit 2 Saving the EarthTopic 2 Section C教案教学目标1. Learn some Learn some new words and phrases: on earth, period, millions of, take away, rise, level, refer to2. Learn some useful sentences:(1) The headroom the sun cant escape (2) When it rains or when the wind blows, the earth is taken away.教学重、难点Learn to talk about the harm of pollution:(1) Forests have become deserts, so more and more sorts of animals and plants are disappearing.(2) As a result, many rivers and lakes are now dead. (3) Too much harmful radiation from the sun passes through the hole and reaches the earth directly.(4) It causes the level of the oceans to rise and the climate of the earth to change.教学准备Tape recorder and some pictures.教学过程Step 1自学导纲通过检查作业，引导学生开拓思维，提出保护环境和水资源的具体措施，复习不定代词和副词。为学习新词汇作准备。T:How do you protect our environment and save water?S1:Everyone should plant more trees.S2:We should do everything we can to save water.S3:Everybody should know the importance of forests.S4:Pass laws against water pollution.S5:Collect and reuse waste water.Step 2合作互动1.教师由日常对话，引出本课话题，呈现部分新词汇。T: Whats the weather like today?Ss: Its T: As we know, Beijing often has sandstorms in spring. What causes the bad weather?Ss: Cutting down too many trees. (展示1a第二幅图画。)T: Yes. All over the world, people have cut down millions of trees. And trees become fewer and fewer.T: Cutting down too many trees causes the bad weather. How can trees affect the weather?S1: They can keep water from running away. S2: They can stop S3: T: Yes. Trees can stop the wind and water from taking the earth away.T: Anything else?Ss:(允许学生用汉语回答。)树能吸收二氧化碳并释放氧气。T: Thats right. Trees can breathe in carbon dioxide and breathe out oxygen.T: Where does CO2 come from?S4: Animals breathing.S5: Burning oil. For example, cars and buses.T: Yes. They have polluted the air. Carbon dioxide in the air has increased a lot. This has formed a “blanket” around the earth.T: The heat from the sun cant escape, so the temperature is rising.T: This is called “the greenhouse effect”.T: Because of the greenhouse effect, what happens to the icebergs(冰川)?Ss: Some parts of them change into water.T: So it causes the level of the oceans to rise.T:(展示1a第4幅图。)Please look at this picture. Around the earth, theres a special kind of oxygen called “ozone”.T: But now air pollution is destroying it and that has made a very big hole in the ozone layer.T: Too much harmful radiation from the sun passes through the hole and reaches the earth.2.教师出示小黑板上的问题，让学生再读一遍课文后回答。(1) Have we changed our planet in many ways?(2) Have people done well to the earth?(3) Why are more and more sorts of animals and plants disappearing?(4) Are many rivers and lakes dead now?(5) Is ozone important to the earth? Why?(6) Has carbon dioxide in the air increased a lot?Step 3导学归纳使学生了解各种污染对地球环境的影响，培养他们的环保意识。(1)changein many ways(2)important, destroy, too much, harmful radiation, cause cancer(3)increase a lot, blanket, rise, change(4