由 if 和unless 引导的条件状语从句教案资料

由if 和unless 引导的条件状语从句

1. If we lose our short-term memory, we forget things happening recently.

译：______________________________________________________

2. If the picture is silly, strange and colorful, you will remember it better.

译：______________________________________________________

A: If sentences: actions with definite results. 有必然结果发生的行动eg: ①If you go into a clothes shop, you find clothes.

②If you go into a car showroom, you see cars.

③Water turns into ice if you cool it.

④The wood floats if you put it into water.

Conclusion:

1). 如果if 条件句谈论的是重复发生和预示必定要发生的情景和事件，则主从句大多用一般现在时态。

2). 在if 条件句中，if 条件从句可以放在前面，也可以放在后面。当if 引导的条件从句放在前面时，后面常用逗号隔开。

B: If sentences: actions with possible results. 有可能性结果发生的行动eg: If you ask him，he will help you．如果你请他帮忙，他会帮你的。

If you fail in the exam，you will let him down．

在if 引导的条件状语从句中,如果从句谈论的是一个有可能发生的事实及其产生的相关的结果，主句用一般将来时态，从句用一般现在时态。

C: unless引导的条件状语从句：unless= if…… not. conj. 除非, 若不, 除非…（否则）

e.g.: Let's go out for a walk unless you are too tired.

= If you are not too tied, let's go out for a walk. 我们出去散步吧，除非是你太累。译：如果你不早点出发,你就不能及时赶到那儿。

我们可以把unless或if…not 从句放在句子开头或末尾。

You will be late for school unless you leave now. =

Unless you leave now, you will be late for school.

除非你早点出发，（否则）你上学会迟到。

You will be late for school if you don’t leave now. =

If you don’t leave now, you will be late for school. 如果你不早点出发，你上学迟到。

“if ” 引导的条件状语从句的用法,现在总结一下:

1)引导条件状语从句最常用的连词是if。if 引导的条件句有真实条件句和非真实条件句两种（非真实条件句会在以后的虚拟语气中阐述），其引导的真实条件状语从句表示在某种条件下某事很可能发生。

2）if 条件句不一般,几个要点记心间; 条件句,放在前,逗号要放句中间。

条件句表可能，主句多用将来时；条件句表事实，主句常用现在时。

【巩固练习】

一．if和unless句型互改。

Eg: You will fail the exam if you don’t work hard.

= You will fail the exam unless you work hard.

1）Unless you obey the rules, you will be punished.

=________________________________________________.

2) A fish dies if you don’t keep it in the water.

=________________________________________________

3) No body can learn English well if he doesn’t work hard on it.

=________________________________________________.

4) Unless you start right now, you will be late for the meeting.

=________________________________________________.

二．用if 或unless 填空。

1. you put wood into water, it floats.

2. I sleep with the window open it is really cold.

3. You will not improve your skill in a short time __ you practice playing the violin regularly.

4. Ice melts you heat it.

5. you boil water, it becomes steam （蒸汽）.

6. you don’t work hard, you will fail the exam.

7. He can’t be here on time he gets up early.

8. you don’t have enough sleep, you will feel tired.

9. it is fine tomorrow, I will go fishing with my dad.

10. you finish your homework, you will not go out to play.

三．单项选择。

1. You will not remember the facts you understand them well.

A. if

B. unless

C. if not

D. because

2. Shenzhen a dirty place if we the ground.

A. is; litter

B. will be; will litter

C. is; are littering

D. will be; litter

3. If you harder, you will fail the exam.

A. not work

B. work

C. don’t work

D. won’t work

4. you obey the rules, you will be punished.

A. If

B. Since

C. Because

D. Unless

5. He can’t see the words o n the board unless he his glasses.

A. wear

B. wears

C. doesn’t wear

D. to wear