Unit 5 动词不定式表目的语法讲解及习题2025-2026学年外研版英语八年级上册

本初中英语讲义聚焦动词不定式表目的这一核心语法点，系统梳理从基本结构（句首/句末作目的状语）到拓展用法（in order to/so as to的位置与否定），再到与so that/in order that从句的对比辨析，以及易混点（表目的与作宾语、to的词性）的学习支架。 资料以分层递进设计（定义-用法-对比-易混点）和多样习题（填空、改写、单选）为特色，通过对比辨析培养思维品质，借助详细解析提升语言运用能力，课中辅助教师高效教学，课后助力学生自主查漏补缺，强化学习能力。

外研版八年级上册Unit 5 语法讲解 动词不定式表目的 一、语法定义 动词不定式（to do）表目的，是指用不定式结构说明动作发生的目的或意图，即“做某事是为了做另一件事”。它在句中可作目的状语，位置灵活，可置于句首或句末。 二、核心用法 用法1：基本结构 · 句末作目的状语（最常用）：主语 + 谓语 + 宾语/状语 + to do sth. 例句： a. He went to the library to borrow some books.（他去图书馆是为了借一些书） b. She studies hard to pass the exam.（她努力学习是为了通过考试） · 句首作目的状语（强调目的）：To do sth., 主语 + 谓语 + 其他. 例句： a. To catch the early bus, he got up at 5 o’clock.（为了赶上早班车，他五点就起床了） b. To improve my English, I take an online course every day.（为了提高英语，我每天上在线课程） 用法2：“in order to do”与“so as to do”的拓展用法 为了更突出目的，可在不定式前加in order to或so as to，三者语义一致，区别在于位置和否定形式： 结构 位置要求 否定形式 例句 to do 句首/句末 not to do I came here to see you.（我来这儿是为了见你） in order to do 句首/句末 in order not to do In order to win, we practiced hard.（为了赢，我们刻苦训练） so as to do 仅句末 so as not to do He spoke quietly so as not to wake the baby.（他轻声说话是为了不吵醒宝宝） 用法3：目的状语的其他表达（对比辨析） · so that + 从句（后接完整句子，常与can/could连用） 例句：He studies hard so that he can pass the exam.（与He studies hard to pass the exam.同义） · in order that + 从句（比so that更正式，可置于句首） 例句：In order that we could arrive on time, we left early.（与To arrive on time, we left early.同义） 三、易混点提醒 1. 不定式表目的与不定式作宾语的区分 · 表目的：不定式是状语，修饰整个句子，说明动作的目的。 例：She bought a pen to write with.（to write with修饰bought，表买笔的目的） · 作宾语：不定式是动词的宾语，是动作的对象。 例：She wants to buy a pen.（to buy a pen是want的宾语） 2. “to”的词性判断：表目的的to是不定式符号，后接动词原形；若to是介词，后接-ing形式（如look forward to doing）。 例：He went to the supermarket to buy food.（to是不定式符号，表目的） 例：He is looking forward to seeing his friend.（to是介词，后接-ing） 语法习题 题型一：用所给动词的适当形式填空 （考查不定式表目的的基本结构与in order to/so as to的用法） 1. She went to the shop ______ (buy) some milk. 2. ______ (learn) English well, he joined an English club. 3. We exercise every day ______ (keep) healthy. 4. He turned on the light ______ (see) clearly. 5. ______ (catch) the train, we left the house early. 6. They study hard ______ (get) good grades. 7. She saved money ______ (buy) a new computer. 8. ______ (finish) the work on time, we need to work together. 9. He opened the window ______ (let) some fresh air in. 10. We read books ______ (gain) knowledge. 题型二：改写句子 （考查不同目的表达结构的转换） 1. I get up early to catch the bus.（用in order to改写） 2. She works hard to pass the exam.（用so as to改写） 3. To make more friends, he joined the sports club.（用in order to改写句首） 4. He spoke loudly to make everyone hear him.（用so that改写） 5. We plant trees to protect the environment.（用in order not to改写否定形式） 6. She studies late to finish her homework.（用so as not to改写否定形式） 7. To improve his writing, he keeps a diary every day.（用so that改写） 8. They saved money to buy a new house.（用in order to改写） 9. He ran fast to catch up with his classmates.（用so that改写） 10. We go to bed early to get enough sleep.（用in order not to改写否定形式） 题型三：单项选择 （考查不定式表目的的结构、in order to/so as to的用法、易混结构辨析） 1. He went to the park ______ a walk. A. to take B. taking C. take 2. ______ late for school, we must get up early. A. To not be B. Not to be C. In order to not be 3. She spoke quietly ______ wake the baby. A. so as to not B. in order not to C. not to 4. I study English hard ______ I can talk with foreigners. A. to B. so that C. in order to 5. ______ the early bus, he got up at 6 o’clock. A. Catch B. To catch C. Catching 6. They are saving money ______ buy a new car. A. to B. in order C. so as 7. She opened the door ______ let her dog in. A. to B. so that C. in order 8. ______ improve his math, he takes extra classes. A. In order to B. So as to C. In order that 9. He worked day and night ______ he could pay off the debt. A. to B. so that C. in order to 10. We keep quiet in the library ______ disturb others. A. so as not to B. not to C. in order to not 习题答案与详细解析 题型一：用所给动词的适当形式填空 1. to buy（句末作目的状语，表去商店的目的是买牛奶） 2. To learn（句首作目的状语，强调学英语的目的，首字母大写） 3. to keep（句末作目的状语，表每天锻炼的目的是保持健康） 4. to see（句末作目的状语，表开灯的目的是看清楚） 5. To catch（句首作目的状语，强调赶火车的目的，首字母大写） 6. to get（句末作目的状语，表努力学习的目的是取得好成绩） 7. to buy（句末作目的状语，表存钱的目的是买新电脑） 8. To finish（句首作目的状语，强调完成工作的目的，首字母大写） 9. to let（句末作目的状语，表开窗的目的是让新鲜空气进来） 10. to gain（句末作目的状语，表读书的目的是获取知识） 题型二：改写句子 1. I get up early in order to catch the bus. 解析：to do表目的可直接替换为in order to do，位置不变。 2. She works hard so as to pass the exam. 解析：to do表目的可直接替换为so as to do，仅能置于句末。 3. In order to make more friends, he joined the sports club. 解析：句首的to do可替换为in order to do，强调目的。 4. He spoke loudly so that everyone could hear him. 解析：to do表目的转换为so that从句，需补充主语和情态动词could。 5. We plant trees in order not to destroy the environment. 解析：否定形式用in order not to do，此处将protect替换为destroy，符合否定逻辑。 6. She studies late so as not to leave her homework unfinished. 解析：否定形式用so as not to do，补充unfinished使语义完整。 7. He keeps a diary every day so that he can improve his writing. 解析：to do表目的转换为so that从句，补充主语he和情态动词can。 8. They saved money in order to buy a new house. 解析：to do表目的替换为in order to do，位置不变。 9. He ran fast so that he could catch up with his classmates. 解析：to do表目的转换为so that从句，补充主语he和情态动词could。 10. We go to bed early in order not to lack enough sleep. 解析：否定形式用in order not to do，将get替换为lack，符合否定逻辑。 题型三：单项选择 1. A 解析：表去公园的目的是散步，用不定式to take作目的状语。 2. B 解析：不定式表目的的否定形式是not to do，句首表目的用Not to be late（为了不迟到）。 3. B 解析：in order not to do是正确的否定结构，so as to的否定是so as not to，A形式错误；C项not to虽可表否定，但此处用in order not to更突出目的。 4. B 解析：后接完整从句I can talk with foreigners，用so that引导目的状语从句。 5. B 解析：句首表目的，用不定式To catch（为了赶上早班车）。 6. A 解析：表存钱的目的是买新车，用to buy；in order后需加to，so as后也需加to。 7. A 解析：表开门的目的是让狗进来，用to let；so that后接从句，in order后需加to。 8. A 解析：句首表目的，用In order to（so as to不能置于句首，in order that后接从句）。 9. B 解析：后接完整从句he could pay off the debt，用so that引导目的状语从句。 10. A 解析：so as not to do是正确的否定结构，in order to的否定是in order not to（C形式错误）；B项not to虽可，但so as not to更强调目的。 ( 1 ) 学科网（北京）股份有限公司 $