问题 选择题

在透明塑料袋中滴入几滴酒精,将袋挤瘪,排尽空气后把口握紧,然后放入80℃以上的热水中,会发现塑料袋鼓起;从热水中拿出塑料袋,过一会儿塑料袋又瘪了。在此过程中酒精发生的物态变化是(    )  

A.先液化后汽化

B.先汽化后液化

C.先升化后凝华

D.先凝华后升华

答案

答案:B

题目分析:物理学中把物质从气态变成液态称为液化,把物质从液态变成气态称为汽化。当把滴入几滴酒精的塑料袋放入80℃以上的热水中时,酒精液体会汽化成酒精气体,体积变大,故发现塑料袋鼓起;当从热水中拿出塑料袋后,气体又液化成酒精液体,体积减小,所以过一会儿塑料袋又瘪了;整个过程的物态变化过程是先汽化后液化;故答案选择:B

点评:此题考查了物态变化过程中的汽化和液化现象,会结合实例分析判断。

阅读理解

阅读理解。

     The first breath-taking pictures of the Earth taken from space showed it as a solid ball covered by brown

land masses and blue- green oceans. We had never seen the Earth from that distance before. To us, it appeared

as though the Earth had always looked that way and always would. Scientists now know, however, that the

surface of the Earth is not as permanent as we had thought.

     Scientists explain that the surface of our planet is always moving. Continents moves about the Earth like

huge ships at sea. They float on pieces of the Earth's outer skin. New outer skin is created as melted rock

pushed up from below the ocean floor. Old outer skin is destroyed as it rolls down into the hot area and melts

again.

     Only since the 1960s have scientists really began to under- stand that the planet Earth is a great living

machine. Some experts have said this new understanding is one of the most important revolutions in scientific

thought. The revolution is based on the work of scientists who study the movement of the continents-a science

called plate tectonics.

     The modern story of plate tectonics begins with the German scientist Alfred Wegener. Before World War

One, Wegener argued that the continents had moved and were still moving. He said the idea first occurred to

him when he observed that the coastlines of South America and Africa could fit together like two pieces of a

puzzle. He proposed that the two continents might have been one and then split apart. 

     Wegener was not the first person to wonder about the shape of the continents. About 500 years ago,

explorers thought about it when they made the first maps of Americas. The explorers noted the east coast of

North America and South America would fit almost exactly into the west coast of Europe and South Africa.

What the explorers did not do, but Wegener did, was to investigate the idea that the continents move.

1. What does the writer mainly tell us in the passage?

A. The first breath-taking pictures of the Earth taken from space.

B. Human's recognition of the earth's surface.

C. The German scientist Alfred Wegener.

D. The early explorers' discovery.

2. Which of the following is true according to the passage?

A. We didn't see the Earth from far away until we saw the picture taken in the space.

B. Our ancient thought that the surface of the earth is still.

C. Alfred Wegener was not the first person to investigate the idea that the continents move.

D. The coastlines of India and Africa fit together.

3. The last word of the third paragraph "tectonics" means "____".

A. study of construction

B. study of architecture

C. earth surface

D. structural geology

选择题