问题 问答题

从H、C、O、Na四种元素中,选择适当的元素符号,用化学式按下列要求填空.

(1)化石燃料,沼气的主要成分:______

(2)重要的化工原料,俗称苛性钠:______

(3)食品工业中发酵粉的成分之一的小苏打:______.

答案

(1)三大化石燃料是煤、石油、天然气,其中天然气的主要成分是甲烷,沼气的主要成分也是甲烷,所以化学式为CH4

(2)氢氧化钠的俗称是苛性钠、烧碱、火碱;钠显+1价,氢氧根显-1价,所以化学式为NaOH;

(3)碳酸氢钠的俗称是小苏打,碳酸氢根显-1价,钠元素显+1价,所以化学式为NaHCO3

故答案为:CH4;NaOH;NaHCO3

阅读理解

How can I get good grades at school? How can I finish so much homework every evening? What should I do if I’m not interested in my classes ? Who will teach us this term ? Maybe you have such questions in your mind before school starts.

Well, I want to give you some good advice on these problems.

First, keep calm.Don’t worry about all the question you have. Put your heart into learning,and you can find something you are interested in.Do it actively.

Second, try your best to finish your homework quickly.Don’t spend a lot of time on it.Do more reading or writing in English.Think about the problems you have and solve them at once.Don’t stay up late,or you can’t study well the next day.

Third, think of something instead of copying or repeating.If you can remember the words in your way,you can tell your teachers you don’t like the way of copying them again and again.Be sure you can pass the test.I think your teachers will agree with you.And they can give you something interesting to do.

School is really a good place for you to learn.Believe in your teachers and yourself.You are the best one and you can do everything well.

小题1:The writer writes the passage to       

A.give students some good ways of learning.

B.ask students not to listen to their teachers.

C.ask students not to do their homework

D.tell students what a good teacher is.小题2:What does the writer tell students to do about their homework?

A.They should spend a lot of time on it.

B.They should stay up late doing it.

C.They should do more reading or writing in English.

D.They should have boring work to do.小题3:What’s the third piece of advice about?

A.How to get on with friends?

B.How to get high grades.

C.What kind of schoolwork is better for students.

D.How to finish the homework in a short time.小题4:According to the passage, students should believe in    

A.themselves and their teachers

B.themselves and their parents

C.their parents and teachers

D.themselves and their classmates

单项选择题