问题 单项选择题

扩散:是指一种物质的分子分散到另一种物质的分子中,最后均匀分布的现象。扩散现象生动地证明,无论是哪一种形态的物质,它们的分子无时无刻不在运动,当它们互相接触的时候,彼此就要扩散到对方当中去。随着温度的升高,分子无规则运动的速度增大,扩散也加快。 根据以上定义,下列属于扩散的是( )。

A.春风杨柳万千条

B.夏日炎炎似火烧

C.金秋桂花遍地香

D.寒冬北国白雪飘

答案

参考答案:C

解析: 扩散的定义中强调的是“分子”的分散运动。A项中的“杨柳”,D项中的“白雪”都不属于分子的范畴。B项描述的对象是温度,也不是分子。只有C项中的“桂花香”是由于分子扩散产生的。举个例子:在烹调的过程中,饭菜的分子有一部分被蒸发到空气中,渐渐地向四面八方运动,当这些气味分子进入鼻腔后,我们就闻到香味了。这个过程叫做扩散现象。正是气体的扩散作用帮助人们闻到了各种气味。同时我们发现,在热锅中加入油,会马上闻到油香味,这正是因为高温使分子扩散加快,符合定义中“随着温度的升高,分子无规则运动的速度增大,扩散也加快”的特征。故本题答案为C。

完形填空

Directions: For each blank in the following passage there are four words or phrases marked A,B,C and D. Fill in each blank with word or phrases that best fits the context.

When I was a young man, I thought life was all about me --- about how I'd make my way in the world, become successful, and get the things I want.    36   then the two of you came into my world with all your curiosity and mischief and those smiles that never    37  to fill my heart and light up my day. And suddenly, all my big plans for myself didn't seem so    38   anymore. I soon found that the greatest joy in my life was the joy I saw in yours. And I    39   that my own life wouldn't count for much unless I was able to ensure that you had every opportunity for happiness and fulfillment in yours. In the end, girls, that's why I  40  President because of what I want for you and for every child in this nation. I want all our children to go to schools worthy of their    41   --- schools that challenge them, inspire them, and instill in them a    42   of wonder about the world around them. I want them to have the chance to go to college ---    43   their parents aren't rich. And I want them to get good jobs: jobs that pay well and give them benefits like health care, jobs that let them spend time with their own kids and    44   with dignity.

Sometimes we have to send our young men and women into war and other dangerous    45   to protect our country --- but when we do, I want to make sure that it is only for a very good reason, that we try our best to settle our differences with others peacefully, and that we do everything possible to keep our servicemen and women    46  . And I want every child to understand that the blessings these brave Americans fight for are not free --- that with the great privilege of being a citizen of this nation     47   great responsibility.

36. A. However                 B. While           C. But             D. Although

37. A. fail                    B. escape          C. drop            D. prepare

38. A. shallow                  B. important            C. respectful          D. delighted

39. A. recognized           B. regretted           C. realized        D. reminded

40. A .searched for            B. accounted for        C. asked for           D. ran for

41. A. potential               B. ability         C. possibility         D. reputation

42. A. sign                B. sense           C. ray             D. bunch

43. A. as if                   B. now that         C. in case             D. even if

44. A. resign              B. resettle            C. retire              D. request

45. A. borders             B. situations          C. nations             D. scenery

46. A. satisfied                   B. fortunate           C. successful      D. safe

47. A. comes               B. goes            C. lies            D. stands

判断题