问题 填空题

氢气和氧气之间发生化学反应的过程,可用下列图示宏观描述.

试回答下列问题:

(1)写出该反应的文字表达式:______.

(2)除化学方程式本身表示的意义外,从如图中你还得到哪些信息?(写出两条即可)

①______;②______.

答案

(1)由反应的过程图可知,反应由氢分子与氧分子反应生成水分子,因此反应的文字表达式为:氢气+氧气

点燃
水;

(2)反应前后分子构成发生改变,但构成分子的原子种类、个数均没有改变,因此可知:化学变化中分子可分原子不可分、一个水分子是由二个氢原子和一个氧原子构成等;

故答案为:(1)氢气+氧气

点燃
水;(2)化学变化中分子可分原子不可分;一个水分子是由二个氢原子和一个氧原子构成(其他合理答案亦可).

单项选择题

A child who has once been pleased with a tale likes, as a rule, to have it retold in almost the same words, but this should not lead parents to treat printed fairy stories as formal texts. It is always much better to tell a story than read it out of a book, and, if a parent can produce what, in the actual situation of the time and the child, is an improvement on the printed text, so much the better.

A charge made against fairy tales is that they harm the child by frightening him or making him sad thinking. To prove the latter, one would have to show in a controlled experiment that children who have read fairy stories were more often sorry for cruelty than those who had not. As to fears, there are, I think, some cases of children being dangerously terrified by some fairy story. Often, however, this arises from the child having heard the story once. Familiarity with the story by repetition turns the pain of fear into the pleasure of a fear faced and mastered.There are also people who object to fairy stories on the grounds that they are not objectively true, that giants, witches, two-headed dragons, magic carpets, etc. do not exist; and that, instead of being fond of the strange side in fairy tales, the child should be taught to learn the reality by studying history. I find such people, I must say so peculiar that I do not know how to argue with them. If their case were sound, the world should be full of mad men attempting to fly from New York to Philadelphia on a stick or covering a telephone with kisses in the belief that it was their beloved girl-friend. No fairy story ever declared to be a description of the real world and no clever child has ever believed that it was.

The advantage claimed for repeating fairy stories to young children is that it ().

A. makes them less fearful

B. develops their power of memory

C. makes them believe there is nothing to be afraid of

D. encourages them not to have strange beliefs

填空题