lesson1Importanceofwater.pptx

Lesson 1 Importance of water Water is the best known and most abundant of all chemical compounds occurring in relatively pure form on the earths surface.Oxygen,the most abundant chemical element,is present in combination with hydrogen to the extent of 89 percent in water.Water covers about three fourths of the earths surface and permeates cracks of much solid land.The polar regions are overlaid with vast quantities of ice,and the atmosphere of the earth carries water vapor in quantities from 0.1 percent to 2 percent by weight.It has been estimated that the amount of water in the atmosphere above a square mile of land on a mild summer day is of the order of 50,000 tons.All life on earth depends upon water,the principal ingredient of living cells.The use of water by man,plants,and animals is universal.Without it there can be no life.Every living thing requires water.Man can go nearly two months without food,but can live only three or four days without water.In our homes,whether in the city or in the country,water is essential for cleanliness and health.The average American family uses from 65000 to 75000 gallons of water per year for various household purpose.Water can be considered as the principal raw material and the lowest cost raw material from which most of our farm produce is made.It is essential for the growth of crops and animals and is a very important factor in the production of milk and eggs.Animals and poultry,if constantly supplied with running water,will produce more meat,more milk,and more eggs per pound of food and per hour of labor.For example,apples are 87%water.The trees on which they grow must have watered many times the weight of the fruit.Potatoes are 75%water.To grow an acre of potatoes tons of water is required.Fish are 80%water.They not only consume water but also must have large volumes of water in which to live.Milk is 88%water.To produce one quart of milk a cow requires from 3.5 to 5.5 quarts of water.Beef is 77%water.To produce a pound of beef an animal must drink many times that much water.If there is a shortage of water,there will be a decline in farm production,just as a shortage of steel will cause a decrease in the production of automobiles.In addition to the direct use of water in our homes and on the farm,there are many indirect ways in which water affects our lives.In manufacturing,generation of electric power,transportation,recreation,and in many other ways,water plays a very important role.Our use of water is increasing rapidly with our growing population.Already there are acute shortages of both surface and underground waters in many localities.Careless pollution and contamination of our streams,lakes,and underground sources has greatly impaired the quality of the water which we do have available.It is therefore of utmost importance for our future that good conservation and sanitary measures be practiced by everyone.1.abundant：充足的、大量的 abundant of eg：Abundant of people participated in the endowment.足够多的人参加了捐赠行动。be abundant with eg：China is abundant with natural resources.中国自然资源丰富。2.in combination with：与联合、与结合 eg：Failure usually comes in combination with misfortunes 失败总是与不幸同时发生。3.to the extent of：达到程度4.quantities：数量，工程量 quantities of +n（可数名词复数或不可数名词）：许多、大量 in quantities：大量地5.three fourths：四分之三 分数是由基数词和序数词一起来表示的。基数词作分子，序数词作分母，除了 分子是“1”以外，其它情况下序数词都要用复数形式。eg：1/2 a half 1/4 one quarter 或 a quarter 3/4 three fourths 或 three quarters 1 1/2 one and a half 当分数后面接名词时，如果分数表示的值大于1，名词用复数;小于1，名词用单数。eg：4/5 meter 五分之四米（读作 four fifths meter）1 1/2 hours 一个半小时(读作 one and a half hours)2 3/4 meters 二又四分之三米(读作 two and three-fourths meters)6.point ：几点几 0.1 ：zero point one 3.5 ：three point five7.（be）of the order of：大约，约为，与相似8.（be）essential to（for）：对是必须的（必不可少的）eg：Money is not essential to happiness.金钱对于幸福并非必不可少.Experience is essential for this job.对于这个工作,经验是非常重要的.9.in addition to：除以外 eg：We play football in addition to basketball.除了篮球外，我们还踢足球。in addition ：此外，另外，还有 eg：In addition,they do not match very much.除此之外，他们两人并不十分般配。We met some friends and other people in addition.我们遇见几位朋友，还遇见其他一些人.