问题 填空题

学校实验室的废液缸中收集了同学们在实验室制取CO2后残留的废液.小红同学想探究废液中溶质的成分,请你一同参与探究并回答下列问题.

[提出问题]废液中的溶质是什么物质?

[作出猜想]小红认为废液中溶质只有CaCl2

你认为还可能含有的溶质是______(填化学式).

[查阅资料]CaCl2溶液呈中性.

[实验与结论]

(1)如果要证明你的猜想是正确的,你选择的试剂是______,实验中可以看到的现象是______.(其它合理答案均可)

(2)若实验证明你的猜想是正确的,要想使处理后的废液只有CaCl2溶液,应向废液中加入过量的______,反应完成后过滤.

答案

[作出猜想]因为反应物中有盐酸,如果盐酸过量,废液中应该还含有盐酸,故可能含有的溶质是HCl.

[实验与结论](1)验证废液中是否含有盐酸,可用紫色石蕊试液,盐酸能使紫色石蕊试液变红.

(2)要想使处理后的废液只有CaCl2溶液,应向废液中加入过量的碳酸钙,这样不但可以除去盐酸,还能够增加氯化钙的质量,而且多余的碳酸钙是固体,反应完成后可以过滤掉.

故答案:[作出猜想]:HCl,

[实验与结论]

(1)紫色石蕊试液;紫色石蕊试液变红,

(2)碳酸钙

阅读理解

阅读理解。

     CHICAGO (Reuters) - Smoking not only can wrinkle (起皱纹) the face and tarn it yellow-it can

do the same to the whole body, researchers reported on Monday.

The study, published in the Archives of Dermatology, shows that smoking affects the skin all over the

body-even skin protected from the sun.

     "We examined non - facial skin that was protected from the sun, and found that the total number

of packs of cigarettes smoked per day and the total years a person has smoked were linked with the

amount of skin damage a person experienced," Dr.Yolanda Helfrich of the University of Michigan, who

led the study, said in a statement.

    "In participants older than 65 years, smokers had significantly more fine wrinkling than nonsmokers.

Similar findings were seen in participants aged 45 to 65 years," Helfrich "s team added in their report.

     The researchers tested 82 people, smokers and nonsmokers, taking pictures of the inner right arms.

They ranged, in age from 22 to 91 and half were smokers.Independent judges decided how wrinkled

each person' s skin was.

     When skin is exposed to sunlight, notably the face, it becomes coarse, wrinkled and discolored with

a pale yellow tint, Helfrich ' s team wrote.

     Several previous studies have found that cigarette smoking contributes to premature(过早的)skin

aging as measured by facial wrinkles, the study said, but little has been done to measure the aging of

skin not exposed to light.

     The report did not discuss die mechanism involved but previous research has found that cigarette

smoke, among other things, causes blood vessels (血管) beneath the skin to constrict (紧缩), reducing

blood supply to the skin.

     Smoking can also damage the connective tissue that supports both die skin and the internal organs,.

1.When your skin is exposed to sunlight long, it-becomes all of the following but _____.

A. flexible

B. coarse

C. rough

D. discolored

2.How wrinkled a person's skin is doesn't relate to _____.

A. the number of cigarettes a person smokes.

B. the kind and characteristics of skin

C. how long a person smokes

D. how long skin is under sunlight

3. From the passage smoking results in skin aging mainly because _____.

A. it will lower blood supply to skin

B. it can make you feel tired

C. it can make skin come off

D. it can make blood run faster

4.The main purpose of the passage is to _____.

A. inform people about the result of the study

B. advise people how to protect skin

C. warn people not to smoke again

D. introduce a new way of avoid skin aging

选择题