Unit 9 When was it invented？
Key points
（No.9 Middle School Yang Xiaohong）
Grammar points
Ⅰ. 语态总述
英语单词有两种语态，即主动语态(The Active Voice)和被动语态(The Passive Voice)。
主动语态表示主语是动作的执行者，被动语态表示主语是动作的承受者。
Ⅱ. 被动语态的构成
被动语态由助动词“be﹢及物动词的过去分词”构成。助动词be有人称、数和时态的变化，其变化规则与be作为连系动词时完全一样。几种常用时态的被动语态构成列举如下：
(p.p=past participle,表示及物动词的过去分词形式)
一般现在时被动语态 am ∕ is ∕ are + p.p
一般过去时被动语态 was ∕ were + p.p
一般将来时被动语态 will ∕ shall + p.p
现在进行时被动语态 am ∕ is ∕ are + being + p.p
过去进行时被动语态 was ∕ were + being + p.p
现在完成时被动语态 have ∕ has + been + p.p
过去完成时被动语态 had + been + p.p
含情态动词被动语态 情态动词 + be + p.p
Ⅲ. 被动语态主要用于以下几方面：
1. 我们不知道或没有必要说明动作的执行者是谁时(这时都不带由by引起的短语)。
eg. Such books are written for children. 这些书是为儿童写的。
We haven’t been told about it.没有人通知我们这件事。
2. 动作的承受着是谈话的中心(这时可带由by引起的短语)
eg. The book was written by Lu Xun.
Man- made satellites have been sent up into space by many countries. (许多国家已向太空发射了人造卫星。
3. 出于礼貌等方面的考虑不愿说出动作的执行者是谁。
eg. He was asked to give a talk about how to learn English well.
Ⅳ. 主动语态变被动语态“三步曲”
1. 变换主语：把主动语态中的宾语变为被动语态中的主语。
2. 变换谓语：把主动语态中的谓语变成被动结构(be﹢及物动词的过去分词)，时态要和原来主动语态的时态保持一致。
3. 用by短语表示动作执行者：原来主动语态中的主语，放在介词by后面，说明动作的执行者。如果不需要说明动作的执行者，也可以省略。
Ⅴ. 主动语态变被动语态“三大注意”
1. 双宾语均作主语：主动语态中若有双宾语(即直接宾语和间接宾语)，变为被动语态时，可将间接宾语(人)变为被动语态的主语，直接宾语留作被动句的宾语；或直接宾语(物)变为被动句的主语。
2. 莫忘记还原to：在主动语态中动词make, see, hear, watch, have等动词后接动词不定式作宾语补足语时，不定式省略to，单变成被动语态时，宾语补足语变成主语补足语，不定式to要还原。
3. 介副词跟上去：在主动语态中，动词短语中的介词或副词在变成被动语态时，仍然要跟在原来动词之后。
Key word points
1. invent ∕ discover ∕ find ∕find out
invent 意思为“发明，创造”，主要指发明一种世界上原本不存在的东西。另外inventor 名词，意为“发明家”。invention 名词，“发明”。
discover 意思为“发现，探索”，指发现一种世界上原本已存在，后来才被人们认识到的东西。
find意为“找到”，强调意外或偶然发现某人或某物。
find out 意为“找出，发现，查明”，指通过观察、调查而发现事实真相。
eg. The light bulb was invented by the great inventor Edison.
Columbus discovered America in 1492.
I want to know where you found your wallet.
The teacher asked me to find out who made our classroom dirty.
2. be used for sth. ∕doing sth. 意为“被用来做……”，表示用途或目的，后接名词或动名词，相当于be used to do sth.
eg Clothes are used for keeping warm.
Knives are used for cutting things.
【注意】①be used as 表示“把……用作”，as是介词，意为“作为”。
The box is used as a table.
The stick is used as a ruler.
②be used by 表示“被……使用”，by介词，后接动作的执行者。
English is widely used by many people.
3. salty 形容词“咸的”，salt+y构成的形容词。
The soup is too salty.
4. by mistake “错误地，由于差错”，介词短语，常在句中作状语。
eg. Potato chips were invented by mistake.
Sorry, I took your book by mistake.
make a mistake 犯错误；mistake…for…把…错当成…
5. by accident 偶然地，意外地。
He broke his arm by accident.
I met one of my old friends on the street by accident.
6.because∕since∕as
because表示的原因语气最强，一般位于主句后面，也可以放在句首。主句前面不能加so,用why提问时，必须用because回答。
since引导的从句的语气次于because引导的从句，表示稍加分析后而推断出来的原因，或指的是人们已知的事实，比as正式，常放在句首。
as语气最弱，其原因只是对结果的附带说明，
eg.1.She failed the math test again because she was too careless.
2.-Why were you late for school ?
-Because I didn’t catch the early bus.
3.Since everyone is here, let’s begin the meeting.
4.As he lives here alone, he has to cook and wash clothes by himself.
7. finally ∕ at last ∕ in the end
Finally 一般指一系列事物或论点的最后一项内容，或用在动词前，表示“等了好久才……”，没有感情色彩。
at last往往表示经过一番努力或曲折之后，带有较强的感情色彩。
in the end相当于at last, finally,其后不接of短语。强调“虽然最初……，最后还是产生了一个……结果”。另外，at the end of…意为“在……结束时，在……尽头”与表示时间或地点的词连用 ；by the end of意为“在……之前，到……为止”，与表示时间的词连用，常与将来时态和过去完成时态连用。
eg.1).Finally, the problem was solved.
Let’s sing a song finally.
2).At last we found his lost boy.
3).The kitchen was too dirty. In the end, I cleaned it with my mother＇help.
8 according to意为“根据……，按照……”。To是介词，后接名词、代词或从句。
eg. According to the plan, we should start at once.
According to what he said, do you believe in him？〉
9. near ∕ nearby
Near是指时间、空间、关系、年龄、程度的接近，表示空间上近距离时，后面加to；near有比较级。
Nearby是指空间接近，既是形容词也是副词。没有比较级。
eg.1).It’s near∕nearly 12﹕30 now.
2).He is near 80 years old.
3).His home is near to our school.
4).The moon is nearer to us than the sun.
5).There is a village nearby.
6).They often go swimming in the nearby river.
10. remain意为“任然是，保持(某种状态) ”，相当于be still,文中用作连系动词。后接形容词、名词、现在分词或介词短语。Remain也可用作不及物动词，相当于stay。
eg. 1.He remained in his office all afternoon.
2.He remains a shop assistant even though his brother has been a famous doctor.
3.A few leaves remained ∕were still on the trees.
11 knock into ∕ knock at ∕ on
knock into表示“与……相撞；把……插到……里”。
knock at ∕ on表示“敲击(门，窗) ”。
eg. When he ran out of his classroom, he knocked into his teacher.
You should knock at ∕ on the door when you enter the office.
12. notice 动词，意为“注意到；察觉到”,后接名词或从句作宾语；也可接复合宾语即notice sb do∕ doing sth.,接不带to的不定式时，指看到一个动作或一件事情的全过程。用动词-ing形式则指看到或听到一个正在进行的动作。
eg 1).Did you notice the book on the desk? 你注意到桌上的那本书了吗？
2).I noticed that he left the room. 我注意到他离开了房间。
3).Did you notice your father leave the room?你注意到你爸爸离开房间了吗？
4).I didn’t notice you carrying a box when you came in. 我没有注意到你进来时搬着一个箱子。
13. on & about 两者都有“关于”的意思。On表示某本书、文章或演说等是严肃的或学术性的，甚至可供研究者参考；about表示内容比较普遍，不那么正式。
eg This is a book on science. 这是一本关于科技方面的书’
What is the article about? 这篇文章是有关什么的？
14. a number of ∕ the number of
a number of表示“许多，大量”，相当于many,a lot of,plenty of.修饰可数名词复数，如果作主语，谓语动词要用复数形式。如果强调数量大，还可以在number前用large, great,good等词修饰，以表示程度。
The number of表示“……的数量”，后面跟可数名词复数，该短语作主语时，谓语动词用单数。
eg.— A number of students come to swim. Do you know the number of them?
—Maybe it’s about fifty.
15.divide…into…表示“把……分成……”。
eg. We divided the students into four groups.
Ten can be divided into three and seven.
本单元重点短语
1. according to 根据，按照
2. be used for 被用于(做) ……
3. by accident 偶然地，意外地
4. by mistake错误地
5. divide…into…把……分成……
6. fall down 倒下，摔倒
7. fall into 落入，陷入
8. in the end 终于，最后
9. in this way 这样
10. knock into… 与……碰撞
11. more than超过，多于
12. since then从那时起
13. the number of ……的数量
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