问题 选择题

下列过程中,不是化学变化的是:(   ) 

A.铁锅生锈

B.煤气燃烧

C.石蜡熔化

D.大米酿酒

答案

答案:C

本题考查的是化学变化和物理变化的判别,化学变化是指有新物质生成的变化,物理变化是指没有新物质生成的变化,化学变化和物理变化的本质区别是否有新物质生成。

A、在铁锅生锈过程中,有新物质铁锈生成,是化学变化,所以错误;

B、在煤气燃烧过程中,有新物质二氧化碳生成,是化学变化,所以错误;

C、在石蜡熔化过程中,只是石蜡的状态发生了变化,没有新物质生成,是物理变化,所以正确;

D、在大米酿酒过程中,有新物质酒精生成,是化学变化,所以错误。故选C

阅读理解

阅读理解。

     A good way to pass an exam is to work hard every day in the year. You may not do well in the exam if

you are lazy for most of the year and then work hard for a few days before the exam. If you are taking an

English exam, don't only learn rules of grammar. Try to read stories in English and speak English when you

can. A few days before the exam, you should start going to bed early, don't stay up late at studying and

learning things. Before you start the exam. read carefully the question paper. Try to understand the meaning

of each question before you pick up your pen to write. When you have at last finished your exam, read over

your answers, find out any mistakes which you see and make sure that you haven't lost anything out.

1. The good way to pass an exam is ________.

A. to work hard at all lessons all the year round

B. to work hard only before the exam

C. to stay up late before the exam

D. to spend all the time remembering rules of grammar

2. Before you start the exam, you should ________.

A. speak loudly

B. learn rules of grammar

C. read carefully the question paper

D. revise your lessons

3. You should _______ your answers before the exam paper is handed in.

A. copy

B. write

C. read

D. cheek

4. Before you pick up your pen to write, you should ________.

A. copy the sentences

B. look up the words in the dictionary

C. revise your book

D. understand the question on the paper

5. Which topic (题目) is the best?

A. Read More Books

B. A Good Way to Pass an Exam Study

C. Do Exercises

D. Hard at Your Lessons

单项选择题