问题 填空题

在相同条件下,等质量的水固态时的体积______液态时的体积;水在______℃时密度最大;纯水极难导电,在水中加入硫酸或______,可增强水的导电性;电解水时应通______电;若在正极得到l0mL______气,同时可在负极得到______mL______气.

答案

水在4℃时密度最大,所以在相同条件下,等质量的水固态时的体积大于液态时的体积;纯水不导电,电解水时为了增强水的导电性可加入硫酸或氢氧化钠溶液,电解时应该用直流电,正极产生氧气,负极产生氢气,并且正负极气体的体积比为1:2.所以正极得到10mL氧气时,负极就会得到20mL氢气.

故答案为:大于  4   NaOH溶液   直流   O2    20   H2

阅读理解

根据短文内容,选择正确选项。

     Cerms(细菌)are everywhere. You can't see them, but they are on your desk,on your computer,and

even in the air!   

     Like people, germs move around the world. They fly with us on planes.When food , clothes,and other

things travel around the world,germs travel , too. Some germs are safe , but some are dangerous. Germs

cause illnesses like colds and the flu.    

     Warmer Weather Brings Germs    

     The world's weather is changing. Cooler countries are getting warmer, so insects from hot countries can move there. Some of these insects, like mosquitoes,carry dangerous germs. Tlhese germs cause

headaches,fevers, and can even kill people.   

     Under Your Skin    

     Your skin protects you from germs.It stops some germs,but not all.They can enter your  body when

you eat,or when you have a cut. Germs are on your hands,too.They enter your body when your touch your eyes,nose, or mouth.    

     Fighting Germs    

     Your immune system (免疫系统)protects you,too. When germs get inside your body, your immune

system finds and kills them. Special cells(细胞)move around your body and fight germs.They help you stay healthy. Other cells make antibodies.Antibodies help your body find and stop germs.    

     What can you do to fight germs?You should wash your hands with soap and water. Soap kills many

germs,and water washes them away.

1. According to the text,insects         .    

    A. kill germs

    B. carry germs  

    C. protect germs

    D. love germs

2. The underlined word"there"refers to            .    

    A. cooler countries    

    B. hot countries    

    C. everywhere    

    D. the world

3. Which of the following is RIGHT according to the text?   

    A. All germs are dangerous.    

    B. There are more germs in cold places.    

    C. Soap can kill all germs.  

    D. Germs can get into your body.

4. What do antibodies do?   

    A. They kill germs and wash them away.   

    B. They find and develop germs.    

    C.They help protect us from germs.   

    D. They carry dangerous germs.

5. Which can be the best title for this text?   

    A. Germs Are Everywhere   

    B. Weather Is Changing    

    C.Skin Stops Germs    

    D.Germs Are Developed

单项选择题