问题 选择题

下列生产过程主要发生物理变化的是(  )

A.煤的干馏

B.石油分馏

C.钢铁生锈

D.高炉炼铁

答案

A、煤的干馏,煤的干馏是隔氧加热、分解,生成焦炭(或半焦)、煤焦油、粗苯、煤气等产物的过程.就是说有新物质生成,所以煤的干馏是化学变化,故A不选.

B、石油分馏,石油的分馏是指利用石油成分的沸点不同,加热使各成分在不同的温度下汽化而进行分离,所以是物理变化,故B正确.

C、钢铁生锈,原因是钢铁生锈后,形成了新的物质铁锈(Fe2O3),属于化学变化;故C不选.

D、高炉炼铁,铁的冶炼原理:在高温下,利用焦炭与氧气反应生成的一氧化碳把铁从铁矿石里还原出来,属于化学变化,故D不选.

故选B

选择题
阅读理解

阅读理解。

      What are the best ways to learn new words? Once you have learned new words, how can you remember

them?

         1   .What is your reason for wanting to improve your vocabulary-for a purpose, like the SAT, or for fun

and general self-improvement?    2    For example, there are books specifically written with methods for

increasing one's vocabulary for SAT test-taking. 

       3   Some people need to use what they learn in order for it to stick-as in conversation and writing.Others

succeed by taking quizzes. Still others are good at memorizing. 

     We tend to remember words more easily when we read about them in meaningful context, when we see

that they are useful and worth remembering, and also when they have been fully explained.    4   Most

word-of-the-day offerings supply the definition as well as an example sentence or two.

     Studies have shown that a new word will stay in your vocabulary if it is regularly reinforced (强化) through

use and reading.    5   It is great to have a quiz book with you when you have to wait in places like a dentist's

office.Keeping a quiz book in the car and on the bedside table is good, too.

A. If you want to learn new words, knowing new words' meanings in your native language is in the first

   place.

B. Also,you can examine how you learn best, especially word-based information.

C. Taking word quizzes is a fun way to spend a few minutes learning words.

D. Getting many kinds of methods towards your learning goal by reading.

E. Knowing how to use a word is just as important as knowing its meaning.

F. If you want to learn new words, you have to take a couple of things into consideration.

G. If you have a goal, it is good to read about different approaches toward achieving the goal.