问题 选择题

下列有关物质的鉴别不能实现的是(  )

A.用水能区分食盐、硝酸铵固体和氢氧化钠固体

B.用燃着的木条就可区分氢气、一氧化碳、甲烷三种气体

C.用氯化钙和酚酞溶液能检验氢氧化钠是部分变质还是完全变质

D.用石蕊溶液或碳酸钠溶液都可以区分稀盐酸、澄清石灰水和蒸馏水

答案

A、食盐溶于水温度变化不大,硝酸铵溶于水温度降低,氢氧化钠溶于水温度升高,故可用水鉴别;

B、氢气、一氧化碳和甲烷都能燃烧,燃烧火焰氢气是淡蓝色,一氧化碳和甲烷燃烧火焰为蓝色,不易区分,故B方法不能实现;

C、将氢氧化钠样品溶于水,加入足量氯化钙溶液,看是否产生沉淀,若产生沉淀,则样品中有碳酸钠,反之没有;然后取上层清液滴入酚酞溶液,看是否变红,若变红,则溶液中有氢氧化钠,则部分变质,若不变红,则完全变质,故C可以鉴别;

D、能使紫色石蕊试液变红的为盐酸,变蓝的为石灰水,不变色的为蒸馏水;能与碳酸钠反应产生气泡的是稀盐酸,产生沉淀的为石灰水,无现象的为蒸馏水,故D方法正确;

故选B.

选择题
阅读理解

Sometimes people call each other "freaked-cat", but have you ever thought about this expression? When a cat is frightened, its heart starts beating faster, its muscles get tense, and there are changes in the chemicals in its bloodstream.Although the cat doesn't realize this, its body is getting ready for action.If the danger continues, the animal will do one of two things.It will defend itself, or it will run away as fast as it can.

Something like this also happens to people.When we are excited, angry, scared, or aroused by other emotions (feelings), our bodies go through many physical changes.Our hearts beat faster, and our muscles get tense.All of these changes make us more alert and ready to react.We, too.get ready to defend ourselves or run.

Human beings, however, have a problem that animals never face.If we give way to our feelings and let them take over, we can get into trouble.Have you ever said something in anger —or hit somebody—and regretted it later? Have you ever shouted at a teacher, told somebody you were lonely, or said you were in love, and then wished later you had kept your mouth shut?

It isn't always clever to express your feelings freely.

Does this mean that it's smarter always to hide our feelings? No! If you keep feelings of anger, sadness, and bitterness hidden away or bottled up inside, your body stays tense.Physical illness can develop.It can actually be bad for your health.(It isn't good to keep pleasant feelings inside either; all feelings need to be expressed.)

Feelings that you keep all bottled up inside don't just go away.It's as if you bought some bananas and stuck them in a cupboard.You might not be able to see them.but before long you' d smell them.And if you opened the cupboard, chances are that you'd see little fruit flies flying all over them.They'd be rotten.

You can try to treat emotions as if they were bananas in the cupboard.You can hide them and you can pretend they don't exist, but they'll still be around.And at last you'll have to deal with them.just like those bananas.

小题1:The best title for this article is_____.

A.Emotions Affect Our Bodies

B.What Happens to A Frightened Cat

C.What Happens to An Excited Person

D.Feelings That People Have小题2:What does the word "freaked" mean in the first sentence?

A.excited

B.scared

C.angry

D.shocked小题3:According to the passage, we may conclude that we human beings_____.

A.have fewer problems than animals

B.have the same problems as animals

C.have more problems than animals

D.have cleverer problems than animals小题4:If you hold in your feelings,_____.

A.gradually they'll disappear

B.they won't exist any more

C.they will fly all over

D.your body stays tense小题5:The author wrote this article in order to_____.

A.tell us that it isn't good to keep feelings inside

B.give us some advice on how to express our feelings

C.make us face the problem that we have to deal with feelings

D.make us know that it isn't always wise to express our feelings freely