试题与答案

用“>”“<”“=”填空: (1)100mL水和100mL酒精混合后的体积 __

题型:填空题

题目:

用“>”“<”“=”填空:

(1)100mL水和100mL酒精混合后的体积 ______200mL

(2)双氧水制取氧气时,反应前二氧化锰的质量 ______反应后二氧化锰的质量

(3)加热高锰酸钾,剩余固体的质量 ______原高锰酸钾的质量

答案:

(1)100mL水和100mL酒精混合后的体积和200mL的关系.题目中考查的是分子之间有间隔,由于不同物质分子本身的大小差异,所以混合时,分子就彼此占据空间,导致总体积小于体积的加和.(但是要注意:一定是不同物质的混合,且比较的是体积而不是质量,即体积不可以简单相加,而质量可以相加)

(2)双氧水制取氧气时,反应前二氧化锰的质量和反应后二氧化锰的质量关系.由于二氧化锰在双氧水的分解反应中作催化剂,所以反应前后质量是没有改变的.

(3)加热高锰酸钾,剩余固体的质量和原高锰酸钾的质量关系.这个题目考查的是质量守恒定律.根据质量守恒定律,

2KMnO4

  △  
.
 
  K2MnO4+MnO2+O2↑,则m(KMnO4)=m(K2MnO4+MnO2+O2).现在对比m(KMnO4)和m( K2MnO4+MnO2)当然就不相等了.

故答案:

(1)<;(2)═;(3)<.

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题型:完形填空

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Online Movie Rentals

It is generally accepted that the best way to learn a language is to totally involve yourself in its culture by living in the country where it is spoken.   71   Fortunately, many aspects of a country’s culture have made their way to our lives in the form of various media and entertainment outlets. Not only do they allow a peek at life, but they make excellent study material for learning the language.

What to increase your language skills and enjoy some entertainment at the same time? Tired of going down to the video rental store to rent movies?   72 

Most companies require customers to operate on the following model:

●Select and sign up for a payment program online, which will determine how many movies you can rent and hold at any one time.

●  73  You can look up movies by title, actor or director. Then movies will be sent to you within 1~3 days, and shipping is covered by the company.

●Watch the movies, often with no late fees.

●  74 

●Check these sites for specific, up – to – date details.

Once you receive the movies, how can you improve your language skills with them? Well, just sitting in front of the TV with a drink in one hand isn’t a bad way to relax, but you won’t learn much. While seeing a movie you should take notes of new expressions. Write them down and look them up in a good English – English dictionary to understand their possible meanings.   75  If you don’t’ know how to use words, learning vocabulary will lose all meaning.

A.Return the movies in a prepaid return envelope.

B.If you haven’t finished on time, you can delay returning.

C.Now, more and more companies are offering customers the chance to rent movies online.

D.Then, think of some sample sentences for each word. E.Choose the movie you want to watch, generally 1~3 at a time.

F.Watch movies as long as you have nothing to do.

G.While many find packing up and moving to a country is not a practical option.

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