Modern Community SchoolWeek of Monday May 18 Grade 10 A / BUnit: Environmental Problems

Check the answer key for the previous assignment. (if you have any questions refer back on the class group)

Read the following text and then answer the questions.

Answer key (Marine Life Literally in Hot Water)

Is DesalinationDesalination the Answer to Water Shortages?

1 If the world needs large quantities of water, one obvious place to get it is from the oceans. It seems so reasonable: When Earth’s growing population runs short of fresh water, water will have to be taken from the sea and desalinated (have the salt taken out).

2 Several different methods can be used to desalinate seawater. Flash evaporation turns the water to steam, leaving the salt behind. The steam is then condensed into fresh water. This is the most widely used method of desalination. Electro-dialysis uses an electric current to remove the salt. Reverse osmosis forces the water through a filter that removes the salt. Direct-freeze evaporation takes advantage of the fact that fresh water freezes at a higher temperature than salt water. Once the fresh water freezes, the fresh water ice crystals are separated from the remaining ingredients. Some of these methods are already used to supply water to areas in the Caribbean, Saudi Arabia, and Texas.

3 The main drawback to desalinated water is that it uses large amounts of costly energy. Desalinated water typically costs $1 per 3,800 liters (1,000 gallons). Water taken from lakes, rivers, and aquifers costs about half as much to domestic users and as little as 5 cents per 3,800 liters for agricultural users. Thus, the added cost of desalination makes this method of supplying fresh water impractical for agricultural needs and for developing nations.

4 Some advocates believe that research into improved desalination techniques will intensify as water supplies become scarcer. One of these advocates is former U.S. senator Paul Simon, now director of the Public Policy Institute at Southern Illinois University in Carbondale. Simon believes that this research may result in new technologies that will eventually lower the cost of desalinating water.

5 But others, such as Peter Gleick, president of the Pacific Institute for Studies in Development, Environment, and Security in Oakland, California, are not so optimistic. “I believe desalination is going to be more important in the future than it is today. We’re going to use it more; it’s going to be cheaper. It’s going to meet high-valued industrial uses. It’s going to be useful in coastal areas [and] for urban supply in some places. It’s just that four-fifths of the water the world uses goes to agriculture, and I do not see desalination providing any of that water,” says Gleick. Briscoe agrees, although he expresses hope that efforts to make desalination cheaper will benefit coastal cities, where about 60 percent of the world’s population live.

I. Comprehension :

1. Why should the world consider desalination?

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2. Complete the following table with reference to the text.

Desalination techniques Detailed process

Turns the water to steam, leaving the salt behind. The steam is then condensed into fresh water.

Electrodialysis

Takes advantage of the fact that fresh water freezes at a higher temperature than salt water. Once the fresh water freezes, the fresh water ice crystals are separated from the remaining ingredients.

3. Say whether these sentences are true or false. Correct the false ones.

a. Desalinated water is cheap.________________________________________________________________________b. U.S. senator Paul Simon is pessimistic about the desalination process. ________________________________________________________________________c. In our world, most people live in the desert._______________________________________________________________________d. Rivers are the best source to find great amounts of water. _______________________________________________________________________

4. What do the underlined words refer to? a. This (par.2):______________________________b. That( par. 3): ____________________________c. Where (par 5):____________________________ 5. Find the antonyms of the following words in the text.a. Advantage (par.3):____________________________b. Next(par.4):_______________________________c. Increase(par.4):____________________________ II. Language: Circle the correct alternative.

A majority of the nation’s biologists are convinced that the mass extinction of plants and animals is already underway and poses a major (threat / threatening / threatened ) to humans in the next century . Yet most people are not ( enough awareness/ aware enough / enough aware) of the problem. The rapid disappearance of many ( houses/ species / people ) was ranked as one of the most hazardous environmental worries, surpassing pollution and global ( warming / warm / warmth ) . The speed at which species are slaughtered is much ( fast / fastest /

faster ) than we ever saw in the past few decades . Up to one fifth of all living species could ( live / disappear / grow ) within thirty years from now.