Unit 13 The Water Planet教案

11)  if a substance has a density 888kg/ m3, it will float on water.
12)  the heat capacity is relatively high, so that most animals don’t like living in it. (temperature stable----like)
13)  the most important thing we can learn about water, is that we must protect it and use it wisely.  (tffffttffttft)
3. multiple choices:
( a )1. based on para. i, the author tells us that there are various species in the oceans, indicating that ____.
a. water plays a great role for marine life.
b. ocean is a good place for life.
c. there are many reasons for tiniest plankton and giants like sharks  and whales
d. ocean is part of the earth
( c ) 2. the water in the ocean is always moving in that _____.
a. the temperature of sea water is relatively high.
b. water’s density affect changes in salinity and temperature.
c. changes in salinity and temperature have effect on water’s density.
d. waters in rivers always flow into the ocean.
( d ) 3. generally speaking ,human beings are ______ to large or suddenly changes in temperature.  
 a.  generous    b. objective   c. subjective  d. sensitive
4. can you answer the following questions?
1) what is the importance of the chemical structure of water?
the chemical structure of water makes it an excellent medium for life and also makes it different from almost everything else on earth.
2) what is the salinity of the earth’s oceans?
the salinity of the earth’s oceans is about thirty-five parts per thousand, meanig that there are about 35 grammes of dissolved solidsand gases in one kilogramme of water.
3) how about density and heat capacity?
density is the relationship between mass and volume, measured in kilogrammes per cubic metre.
heat capacity the amount of energy it takes to raise the temperature of a substance by one degree centigrade.
5. further understanding by looking at some pictures:
 
 
 
read following statement and think what conclusion you can draw? or what property does it refer to?
it is said that a man of 60kg loses about 1l water through breath and skin evaporation (皮膚蒸發(fā)) every day. in other words, 539kcal heat is released in these two ways. if so much heat were kept in human body, it would raise body temperature by 9℃.
can you imagine the result?
water has a relatively high heat capacity and can accommodate the climate automatically. it can absorb and release a lot of heat without big changes in its temperature, thus creating a stable environment.