问题 问答题

学习的目的是在于应用.请根据你所掌握的化学知识,解释或解决以下生活中的一些常见问题.

(1)要区分硬水与软水,可以使用的物质是______;

(2)进行水的净化时,除去其中的难溶性杂质应采用的方法是______;

(3)要区分一氧化碳和二氧化碳两种无色气体,可采用的方法是______;(写一种即可)

(4)为保证人身安全,进入久未开启的菜窖前,须做______试验;

(5)点燃可燃性气体前应进行______.

答案

(1)向等量的两种水样中分别加入等量的肥皂水,振荡,泡沫多的是软水,泡沫少的是硬水.

(2)过滤是把不溶性的固体和液体分开的分离和除杂的操作,所以除去水中的难溶性杂质用过滤的方法.

(3)由于二氧化碳能与氢氧化钙反应生成碳酸钙沉淀,而一氧化碳与氢氧化钙不反应,故可将两种气体分别通入澄清的石灰水,看澄清的石灰水是否变浑;由于二氧化碳能与水反应生成碳酸,所以可将两种气体分别通入紫色的石蕊溶液,看溶液是否变红(合理即可).

(4)二氧化碳的密度比空气大,易聚集于久未开启的菜窖,且二氧化碳不能供给呼吸,含量过高会使人窒息死亡,所以进入久未开启的菜窖前,须做灯火实验.

(5)可燃性的气体与空气混合后点燃易发生爆炸,所以点燃可燃性气体前应先检验气体的纯度.

故答案为:

(1)肥皂水;

(2)过滤;

(3)分别通入澄清的石灰水,看澄清的石灰水是否变浑(或通入紫色的石蕊溶液,看溶液是否变红,合理即可);

(4)灯火;

(5)验纯.

阅读理解

While it is impossible to live completely free of stress, it is possible to prevent stress as well as reduce its effect when it can’t be avoided. The US Department of Health and Human Services offers the following suggestions for ways to deal with stress.

Try physical activity

When you are nervous, angry or upset, try releasing the pressure through exercise or physical activity. Running, walking, playing tennis, or working in your garden are just some of the activities you might try. Physical exercise will relieve your anxiety and worry and help you to relax. Your body and your mind will work together to ease the stress in your life.

Share your stress

It helps to talk to someone about your anxieties and worries. Perhaps a friend, family member, teacher or even your leader can help you a better view of what’s troubling you. If you feel your problem is serious, you might seek professional help from a psychologist or a doctor. Knowing when to ask for help is an important step in avoiding serious problems later.

Take care of yourself

You should make every effort to eat well and get enough rest. If you easily get angry and cannot sleep well enough, or if you’re not eating properly, it will be more likely that you will fall into stressful situations. If stress repeatedly keeps you from sleeping, you should consult a doctor. Make time for yourself.

Make a list of the things you need to do

Stress can result from disorganization and a feeling that "there’s so much to do, and not enough time". Trying to take care of everything at once can be too much for you and as a result, you may not achieve anything. Instead, make a list of everything you have to do, then do one thing at a time, checking off each task as it is completed. Set out to do the most important tasks first.

Go ahead and cry

A good cry can be a healthy way to bring relief to your anxiety. It might even help you avoid a headache or other physical effect of anxiety and stress.

小题1: What is most probably the writer’s purpose in writing the article?

A.To release his or her working tiredness.

B.To help solve the universal problem of stress.

C.To strengthen his or her anxiety.

D.To have more people cry out.小题2: Physical activity can help people release stress because________.

A.only your body movement can help you relax

B.your mind can work better to free you of anxiety

C.your body and mind can cooperate in releasing stress

D.physical activity doesn’t play an important part in reducing nervousness小题3: What is similarity between "Share your stress" and "Go ahead and cry"?

A.They both help you let out your feelings.

B.They both need physical movement.

C.They both require mental relaxation.

D.They can cause a headache.小题4: The underlined sentence is close to the meaning of "________".

A.Strike while the iron is hot

B.More haste, less speed

C.Practice makes perfect

D.Quietness wins time

单项选择题