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问题 填空题

把下列各符号表示的意义填写在空格内：

⑴ H________________________  ⑵ 2H_____________________

⑶ H2_______________________  ⑷ 2H2_____________________

答案

把下列各符号表示的意义填写在空格内：

⑴ H_氢元素，一个氢原子    ⑵ 2H两个氢原子

⑶ H2氢气，一个氢分子      ⑷ 2H2__两个氢分子_

考点：

专题：化学用语和质量守恒定律．

分析：根据化学式的宏观、微观含义进行解答本题．

解答：解：（1）H 表示：氢元素或一个氢原子； 故答案为：氢元素或一个氢原子； 

（2）根据标在元素符号前面的数字表示原子的个数；因此2H 表示：2个氢原子；  故答案为：2个氢原子；

（3）H2表示：氢气或一个氢分子；   故答案为：氢气或一个氢分子；

（4）根据标在化学式前面的数字表示分子的个数；因此2H2表示：2个氢分子；故答案为：2个氢分子．

点评：本题主要考查学生对化学用语的书写和理解能力，题目设计既包含对化学符号意义的了解，又考查了学生对化学符号的书写，考查全面，注重基础．

单项选择题

空气采样的基本原则，包括选择合理的（）

A.采样方法

B.采样地点

C.采样频率

D.采样时间与品数

E.全包括
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完形填空

Have you ever been in a meeting while, someone was making a speech and realized suddenly that your mind was a million miles away? You probably felt sorry and made up your mind to pay attention and ever have been told that daydreaming is a waste of time.
“On the contrary,” says L. Giambra, an expert in psychology, “daydreaming is quite necessary. Without it, the mind couldn't get done all the thinking it has to do during a normal day: You can't possibly do all your thinking with a conscious mind. Instead, your unconscious mind is working out problems all the time. Daydreaming then may be one way that the conscious and unconscious states of mind have silent dialogues.”
Early experts in psychology paid no attention to the importance of daydreams or even considered them harmful. At one time daydreaming was thought to be a cause of some mental illnesses. They did not have a better understanding of daydreams until the late 1980s. Eric Klinger, a professor of psychology, is the writer of the book Daydreaming. Klinger says, “We know now that daydreaming is one of the main ways that we organize our lives, learn from our experiences, and plan for our futures: Daydreams really are a window on the things we fear and the things we long for in life.” Daydreams are usually very simple and direct, quite unlike sleep dreams, which may be hard to understand. It's easier to gain a deep understanding of your life by paying close attention to your day dreams than by trying to examine your sleep dreams carefully. Day dreams help you recognize the difficult situations in your life and find out a possible way of dealing with them. Daydreams cannot be predicted, they move off in unexpected direction which may be creative and full of ideas. For many famous artists and scientists, daydreams were and are a main source of creative energy.
About Daydreams
Attitudes
Advantages
小题1:   ___   
小题2:   ___   　
 
A. 小题3: ___   : one way that the     小题4:     states of mind have      小题5: ____   .
organize our lives;
not be predicted
A. daydreams:
小题6:  ___      
小题7: _______  ;
B. harmful : 小题8:     ______  of some mental illnesses.
小题9: ____      
B.小题10:_____ :
Hard to understand
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