问题 选择题

水煮沸时,水面上不断向上冒“白气”,从水到“白气”形成的物态变化过程是:[ ]

A.先液化后汽化

B.先汽化后液化

C.只有液化

D.只有汽化

答案

答案:B

题目分析:
物体由液态变为气态的过程叫汽化,由气态变为液态的过程叫液化。水沸腾是一种剧烈的汽化现象,此过程产生大量的水蒸汽,但水蒸气看不见,水蒸气上升后遇冷液化形成白气。
故选:B.
 
选择题
阅读理解

Uganda is a country in East Africa and,as in many such countries,a high percentage of the population,about 80 percent,are village-dwellers living in huts,which are often no bigger than a garage. The walls of the huts are made of mud,which is held together by reeds and sticks,and the roofs of the older ones are thatched(覆盖)with grass,although an increasing number of newer village houses have roofs made from corrugated(波纹形的)iron.

Several generations of the same family live together in the huts,which are usually divided into two sections by a curtain. The inner section,the one furthest from the open door of the hut,is where everyone sleeps and food is prepared and served in the outer part. If the family owns chickens or goats,they are kept in a small room attached to the main house.

Food is usually prepared on open fires although some people prefer to cook inside. However,this is quite dangerous and also means that the walls of the hut are stained by smoke and the atmosphere is acrid. The family sit in a circle on mats while they eat.

Newer village houses are almost always made of corrugated iron and are bigger,with one or two separate bedrooms and the kitchen in a smaller building beside the main house. But,old or new,the houses are not powered by electricity,and all homes are lit by paraffin(石蜡)candles called “tadobba”.

Nor is there any running water in the houses. Some villages have their own well,but in many cases,collecting water involves a long and arduous walk to a river or spring,carrying plastic containers or pots made of clay.

Children are the ones who have to fetch water,and they have to do this early in the morning before they go to school,or in the evening when they come home. They often have to climb high hills or walk through valleys with narrow paths through dense vegetation. It is no surprise that they grow up muscular and fit after such daily exercise,walking for several kilometres carrying such heavy weights.

小题1:Most Ugandans live        .

A.with their whole family in large mud houses in the countryside

B.in towns in small houses made of mud and iron

C.in villages in small houses made of wet earth,grass and wood

D.With their parents and children as well as their chickens and goats小题2:Where is food usually prepared?

A.In the kitchen.

B.On the floor in the middle of the house.

C.On fires in front of the hut.

D.In a small room attached to the main house.小题3:How are the old and new houses the same?

A.Both of them have roofs made of corrugated iron.

B.Neither of them have a garage or kitchen.

C.Neither of them have electricity,lights or running water.

D.Both of them have water inside but no electric light.小题4:The majority of Ugandan children have to          .

A.go to a well or a river and often carry it for a long distance

B.do a lot of work cooking and carrying water

C.collect water on the way home from school

D.get water out of their own well