问题 选择题

某学生做了如下实验:将一个不与盐酸反应的小球放入盛有盐酸的烧杯中,小球漂浮于液面(如图).将适量锌粒加入烧杯中,至不再产生气泡为止(溶液的体积变化忽略不计).与开始相比,小球浸入液体中的体积(  )

A.变小

B.变大

C.不变

D.无法确定

答案

将锌片投入烧杯中,锌与盐酸反应,生成氯化锌和氢气,溶质由氯化氢变为氯化锌,则溶液的密度增大,小球漂浮于液面上,则所受的浮力不变,根据公式F=ρgv,ρ增大,则v减小,所以小球上浮;

故选A.

阅读理解

任务型阅读。阅读短文,并按要求完成下列试题。

    Sudden shaking of the ground makes an earthquake. It is caused by a sudden rock movement underground.

Earthquakes usually happen in long narrow belts, where different large plates of rock meet.

    In spite of much research and wonderful equipment, it is impossible to predict an earthquake accurately (准

确地), although experts can estimate roughly (大概推测) an earthquake coming in a particular region. So

everyone needs to learn a bit about how to keep oneself safe in an earthquake. As you may know, the greatest

danger of an earthquake comes from falling buildings and structures and flying glass, stones and other objects.

Please read on for some tips about how to stay safe in an earthquake:

    ●If you are indoors, find a secure location to wait out the quake, such as under a heavy table or desk. Door

        ways are among the safest places to stand because you can brace (支撑) yourself between two walls.

        However, watch out for swinging doors. Stay away from windows.

    ●If you are outdoors, try to get into an open area, away from falling buildings, power lines, trees, etc.

    ●If you are in a crowded public area, crouch down (蹲下), with your hands protecting your head and neck. 

    ●If you are in your car, pull over to the side, away from power lines and overpasses, and stay inside the

        car until the shaking stops.

判断正误、英译汉及回答问题。

1. We can predict an earthquake accurately now. ( T or F )

    ___________________________________________________________

2. Put the underlined sentence (in Paragraph 2) into Chinese. 

    ____________________________________________________________

3. What causes an earthquake?

    ____________________________________________________________

4. How do we protect ourselves if we are in a crowded public area?

    ____________________________________________________________

5. What is this passage mainly about?

     ____________________________________________________________

单项选择题