问题 选择题

鉴别日常生活中的下列各组物质,其操作不正确的是   

A.软水和硬水: 滴加肥皂水

B.CO和CO2:滴加紫色石蕊试液

C.N2和CO2: 伸入燃着的木条

D.H2和O2: 点燃

答案

答案:C

题目分析:根据所要鉴别的物质的性质分析、判断。

A、向硬水和软水中分别加入肥皂水,泡沫少者为硬水,泡沫多者为软水,正确;

B、把CO和CO2气体分别通入紫色石蕊试液,能使紫色石蕊试液变红的气体为二氧化碳,无明显变化的为一氧化碳,正确

C、由于N2和CO2都不可燃,也不助燃,故当燃着的木条分别伸入两个集气瓶中,都会熄灭,故无法区分,错误;

D、氢气具有可燃性,氧气具有助燃性,故氢气能被点燃,而氧气不能,故用点燃的方法可以区分,正确。故选C

点评:区分或鉴别物质时,所选取的试剂或方法应能与待区分的物质发生变化而出现明显不同的实验现象。

阅读理解

BASEBALL. It’s just a word, but for millions of Americans it brings much more than a word.

Hot dogs. Cold beers. Sunny afternoons. Baseball is the game of fathers and sons. Fathers and sons catch with each other on lawns (草坪) in the US. A father’s favorite team becomes his son’s. Grandfathers talk to their grandsons about games played long ago.

Many American kids collect baseball cards. The cards have pictures of their favorite players on them. In school, friends trade (交换) baseball cards just like they trade their lunches.

Players are known as “the boys of summer” because people often play the sport mostly in warm months. You don’t need to be of a certain size or shape to play baseball. You don’t have to be tall like a basketball player or strong like an American footballer. You just need to want to have fun.

Baseball is not as fast-paced (快节奏的) a game as basketball. But when you go to see a game, there’s time to relax, talk and get to know other people.

Baseball may not be the most popular sport in the US, but it is the most traditional. It’s not just a game any more, but an important part of American culture, like apple pie and grandma’s house.

小题1:Many American kids like to collect _______________.

A.baseballs

B.baseball cards

C.lunches

D.apple pies小题2:People like to play baseball in _____________.

A.wet months

B.cool months

C.warm months

D.cold months小题3:Most of the Americans play baseball just want to _______________.

A.enjoy themselves

B.make money

C.keep warm

D.make friends小题4:Which one is WRONG in the article?

A.We can find many children’s favorite baseball players on their cards.

B.If you are not strong enough, you can’t play baseball.

C.When you go to watch a baseball play, you’ll relax and have time to talk to other people.

D.Baseball is the most traditional sport in the US.

问答题