问题 填空题

通过一段时间的化学学习,我们熟悉了许多物质。请从①氮气; ②石墨; ③氧气;④氢气; ⑤纯碱; ⑥一氧化碳中,选择相应的物质填空(写化学式):

(1)最清洁的燃料是    ;              (2)常用于食品防腐的是    

(3)家庭制作馒头添加的“碱”    ; (4)可用作干电池电极的是    

(5)炼钢时需要的助燃剂是    ;  (6)具有可燃性的有毒气体是    

答案

(1)H2  (2)N2   (3)Na2CO或Na2CO3 ·H2O(4)C  (5)O

(6)CO

题目分析:根据常见物质的组成和性质分析。

(1)由于氢气燃烧只生成水,没有污染,故为最清洁的燃料,故化学式是H2

(2)由于氮气性质不活泼,故常填充于食品袋,用于食品防腐,故化学式为N2

(3)家庭制作馒头添加的“碱”,不是碱,而是盐,是碳酸钠,因为碳酸钠能与面粉发酵产生的酸反应,且能产生气体,故为Na2CO3

(4)石墨具有优良的导电性,故可用作干电池的电极,化学式为C;

(5)炼钢时需要的助燃剂是氧气,因为氧气具有助燃性,化学式为O2;  

(6)具有可燃性的有毒气体是一氧化碳,故化学式为CO。

点评:本题较简单,熟练掌握常见物质的组成特点和性质,以及常见物质的化学式即可轻松作答。

单项选择题
单项选择题

Is test anxiety destructive. Can we make test anxiety work for us The answer to both of these questions is yes. Test anxiety often interferes with student performance but this same test anxiety, if channeled correctly, can help improve performance.
In order to lessen the destructive elements of test anxiety, the approach should be to develop improved confidence and knowledge. As your knowledge of the course material increases, your confidence in your ability to succeed will increase. As your confidence increases, your anxiety will go down, allowing your knowledge to come through more efficiently. The way you prepare for a test can reduce anxiety during the test.
You will be surprised how confident you will feel if you know the material. Studies of memory show if you want to be able to recall information from text or lecture you have to review that material several times. It is important to know your own abilities and operate accordingly. If you know that you learn best by listening, prepare a tape of significant material and listen to the tape.
Study partners or study groups are often useful for self-testing. Experience in stressful situations tends to lessen anxiety in those situations. One way to help yourself retrieve material is through the use of mnemonic codes. Learn a code that lets you remember complex material. Developing an outline for an essay question that you know will be on the test or memorizing a formula are forms of code development.
Students are often frustrated by the sheer volume of material that has to be studied in college. Many instructors conduct reviews, give hints, identify what is important to study, use handouts or overhead transparency outlines. These materials should be at the top of your study list. If the instructor took the time to identify them, you should assume that they will play an important part of the test. While knowledge acquired during test preparation can help reduce anxiety, it is another thing to take the test itself. Following are a few suggestions to help reduce anxiety during the test.
When I arrive at a test, I often find students flipping text pages at the last minute trying to cram it all in at the end. You would be better off trying to relax, meditating a little, and clearing your mind to allow yourself the ability to concentrate on the questions that are coming.
As soon as the instructor gives you the signal to start, dump out formulas, codes, outlines from your memory onto the test answer sheets so that you will not have to worry about whether you will remember the codes long enough until you get to the appropriate test question.
You can build your confidence if you go through the test and answer all of the questions that you know first. Go back and work on those questions that need greater analysis, or that need to be worked out or need to be guessed at and your anxiety will not kick in until later in the test.
For those of you whose anxiety increases as study and preparation increase, your goal should be to start concentrating on things that take your mind off the test, i. e. , television, books, hobbies, movies, etc. Meditation and aerobic exercise have proven to be very useful methods for reducing undesirable effects of stress.
The solution to reducing the destructive influences of stress is to plan to study. Map out a schedule of when you will study each day. Identify the specific topics that you will study each day. Identify the areas of the material that you have had problems with and study those. Your plan should include reading the text material, reviewing notes and homework assignments, identifying material that needs further explanation, developing codes for memory material and testing yourself. Once you have studied adequately, your confidence will be fairly high, your knowledge will be satisfactory to do well on the test and the stomach butterflies will help you focus on the task at hand.
I’d wish you good luck on finals, but you and I both know that the more effectively you study, the luckier you will get.

What should be at the top of your study list when you prepare a test

A.The most complex materials.

B.The questions asked by students.

C.The materials reviewed and hints given by the teacher.

D.The materials mastered by most students.