Unit 13 The water planet教學設(shè)計
tip two
if we are writing about something that has several parts, we should describe each part and explain its function and structure.
the following questions may help:
what is it? how many parts is it made up of?
what’s the structure of each part? how does it work?
step 5. homework
imagine that your science teacher ask you to explain one of the following questions:
why does an ice cube float?
what will happen to a piece of metal if you put it in water?
why do so many species live in estuaries?
why have so many cities been built by estuaries?
choose one of the questions and write a passage, using what you know about nature and science and what you have learned from this unit.
period 5 grammar: modal verbs
teaching aims and demands:
to review modal verbs ( to enable the ss to grasp some important modal verbs and some important usages of them .)
teaching difficult points:
1. to grasp the differences among some modal verbs
2. to learn how to use them.
teaching aids:
some worksheets and some slides.
teaching procedures:
step1. check the answers to exercise1 on p21.
step 2. review modal verbs.
1 情態(tài)動詞的語法特征
1） 情態(tài)動詞不能表示正在發(fā)生或已經(jīng)發(fā)生的事情，只表示期待或估計某事的發(fā)生。
2） 情態(tài)動詞除ought 和have 外，后面只能接不帶to 的不定式。
3） 情態(tài)動詞沒有人稱，數(shù)的變化，即情態(tài)動詞第三人稱單數(shù)不加-s。
4） 情態(tài)動詞沒有非謂語形式，即沒有不定式，分詞，等形式。
2 比較can 和be able to
1）can/could 表示能力；可能 （過去時用could）, 只用于現(xiàn)在式和過去式（could）。be able to可以用于各種時態(tài)。例如：
they will be able to tell you the news soon. 他很快就能告訴你消息了。
2）只用be able to的情況：
a. 位于助動詞后。 b. 情態(tài)動詞后。 c. 表示過去某時刻動作時。 d. 用于句首表示條件。
e. 表示成功地做了某事時，用was/were able to，不能用could。例如：
he was able to flee europe before the war broke out. = he managed to flee europe before the war broke out.
注意：could有時不表示時態(tài)
1）提出委婉的請求，（注意在回答中不可用could）。例如：
--- could i have the television on? 我能看電視嗎？
--- yes, you can. / no, you can't. 可以/不可以。
2）在否定句、疑問句中表示推測或懷疑。例如：
he couldn't be a bad man. 他不大可能是壞人。
3 比較may和might
1） 表示允許或請求；表示沒有把握的推測；may 放在句首，表示祝愿。例如：
may god bless you! 愿上帝保佑你！
he might be at home. 他可能在家。
注意：might 表示推測時，不表示時態(tài)，只是可能性比may 小。
2） 成語：may/might as well，后面接不帶to 的不定式，意為"不妨"。例如：