问题 填空题

根据图溶解度曲线:

(1)______℃时,甲乙两物质溶解度相等

(2)当甲中含有少量乙时,可采用______的方法提纯甲

(3)t2°C时,60克甲的饱和溶液蒸干后得到10克甲的固体,该温度下甲的溶解度是______克/100克水.

答案

(1)曲线中交点表示该温度时两种物质的溶解度相等,所以t2°C时甲乙两物质溶解度相等;

(2)如果溶解度受温度影响较大的物质从溶液中结晶析出的方法是冷却热饱和溶液,如果溶解度受温度影响不大的物质从溶液中结晶析出的方法是蒸发溶剂,由于甲的溶解度随温度变化比较大,所以用冷却热饱和溶液的方法;

(3)根据60克甲的饱和溶液蒸干后得到10克甲的固体,可知50克水中最多溶解了10克甲固体,所以100克水中最多溶20克,所以t2°C时,甲的溶解度是20克.

故答案为:(1)t2;(2)冷却热饱和溶液;(3)20.

阅读理解

Long, long ago there were only a few thousand people in the world. These people move form place to place over the land, hunting animals for food.

No one knows how or when these people learned about growing food. But when they did, their lives changed. They did not have to look for food any more. They could stay in one place and grow it.

People began to live near one another. And so the first village grew. Many people came to work in the villages. These villages grew very big. When machines appeared(出现), life in the villages changed again. Factories were built. More and more people lived near the factories. The cities grew very big.

Today some people are moving back to small towns. Can you tell why?

小题1:The best title(题目)of the text should be ___.

A.Cities or Villages

B.Back to Towns

C.How Cities Grew

D.People and Animals小题2:The underlined word "they" in the second paragraph refers to(指的是) ___.

A.villages

B.animals

C.cities

D.people小题3:When factories were built, ___.

A.more people live near the factories

B.people began to live in the factories

C.many people began to work in villages

D.many machines appeared in big factories小题4:We can learn from the text that ___.

A.people like to work only in big cities

B.some people don't like to live in big cities

C.there will be no small towns in the future(将来)

D.it is better to live in cities than in villages小题5:In what order did people do the following things?

A. Worked in villages       B. Lived near the factories.

C. Learned to grow food.    D. Built factories.

E. Began to live near each other.

A. d, b, a, e, c         B. e, a, c, d, b

C. c, e, a, d, b         D. a. c. d. e. b

问答题 论述题