8年级条件状语从句
一、If引导的条件句
*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。

1、“if从句（一般现在时）+主句（一般现在时）”的条件句----表达真理或事实（动作必然发生）。

If you heat ice, it turns into water.如果你加热冰，它就会变成水。

If you put suger into water, it disappears.如果你把糖放进水里，它就会溶解。

2、“if从句（一般现在时）+主句（一般将来时）”的条件句----谈论可能发生的的事情。

If it rains tomorrow, we’ll stay at home.如果明天下雨，我们会呆在家里。

If I don’t hear from him, I won’t go. 如果没接到他的通知，我不会去。

【注】这类条件句主句部分还可以用情态动词，如
I may buy a car if I pass the driving test.如果通过驾驶考试，我可能会买一辆车。

If you go to another country, you must obey the local laws.如果你去另一个国家，就必须遵守当地的法律。

3、有时if引导的条件句可以与“祈使句，and/or…”相互转换，
If you don’t hurry up, you will miss the bus.
=Hurry up, or you will miss the bus.快点，否则你会错过这趟车。

If you use your head, you’ll find a way.
=Use your head, and you will find a way.动动脑子的话，你就会想出办法。

二、unless引导的条件状语从句
unless意为“除非、如果不”，用来引导否定意义的条件句，等于“if…not…”
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。

Unless you brush your teeth every day, you will get a toothache.
=You will get a toothache if you don’t brush your teeth every day. 如果不每天刷牙，你就会牙疼。

完成句子
1. If I feel tired,_______________________( go / bed)
2. If I stay up late, _______________________ (feel/ tired)
3. If I feel hungry, _______________________ ( eat/ something).
4. If I eat too much, _______________________ ( get/ fat).
5. If I feel ill, _______________________ ( see/ doctor).
用unless改写句子
1. If you haven't listened carefully, you won't know how to do the exam questions.
2. If I don't leave now, I will be late.
3. We will get lost if we don't have a map.
4. If you don't return your book to the library today, you will be fined.
5. I will buy that dress if someone hasn't bought it already.
用if 或unless填空
1. _______he wants to see me, you can tell him to wait.
2. _______it snows tomorrow, we’ll have a day or two off.
3.We won’t go to his party_______he invites us.
4.She is sure to pass the exam_______she is ill.
5. _______I’m tired, I’ll have a rest for tea.
6.I won’t buy that backpack_______it costs less than 100 yuan.
7. I will lend you the money_______you pay back on time.
8. You will fail the exam_______you study hard.
9.I will buy a computer_______I am able to save enough money.
10. _______you drop a glass, it breaks.
单选
1. If I ________ his phone number, I will tell you.
A. find
B. found
C. will find
D. have found
2. We will go camping if it _______ tomorrow.
A. Won’t rain
B. didn’t rain
C. doesn’t rain
D. isn’t raining
3. I’m waiting for my friend. If he _______, I ______ swimming alone.
A. doesn’t come; will go
B. won’t come; will go
C.will come; won’t go
D. don’t come; will go
4. ______ you go to the supermarket at 7 p.m, you can buy a lot of cheap food.
A. If
B. Unless
C. Whether
D. When
5. I won’t get to the party on time ______ I catch the first train tomorrow morning.
A. If
B. Unless
C. Whether
D. When
6. ------Shall we go on a picnic this weekend? ------Good idea! Unless it _______.
A. rains
B. doesn’t rain
C. rain
D. won’t rain
7. -----Can I change the jacket for another one ______ it doesn’t fit me well? ----- Of course.
A. unless
B. if
C. that
D. though
8. -----if I get good grades this time, my parents _____ me to Hong Kong for a five-day trip.
A. take
B. takes
C. took
D. will take
9.If everyone ____ the traffic rules, the roads will be much safer (安全得多).
A. obey
B. obeys
C. obeies
D. obeying
10.We mustn't cross the road if the light _____ red.
A. turning
B. are
C. turns
D. is
ACAAB ABDBD。