问题 填空题

(8分)人类的日常生产、生活都离不开水。

(1)化学课上同学们分组研究水的净化及组成(装置如图)。其中一组同学用自制简易净水器(图②所示)净化池塘水,其中活性炭的作用是        ,净化后的池塘水与矿泉水、蒸馏水、自来水四种水中属于纯净物的是_________。

          

(2)实验③中通电一段时间后,试管b中气体的气体是       (填写化学式),该

实验说明水是由          组成的,反应的化学方程式为               

(3)请根据电解水的微观示意图分析:由于化学反应前后原子的                 和质量都没有发生变化,因此在化学反应中质量守恒。

(4)从微观角度分析,实验①和③两个变化中最本质的区别是                 

答案

(共8分)

(1)吸附 蒸馏水               ………………………………………………各1分

(2)O2                         …………………………………………………1分

氢元素和氧元素                                   ……………………1分

2H2O2H2↑ + O2↑                             ……………………1分

(3)种类、数目                  ……………………………………………各1分

(4)①中只是水分子的间隙变大,③中水分子变为氢分子和氧分子。 …………1分

活性炭具有吸附作用,能够吸附水中的色素和异味;纯净物是由一种物质组成的物质,混合物是由多种物质组成的物质;进行分析解答.性炭具有吸附作用,能够吸附水中的色素和异味,故制简易净水器中的活性炭起吸附作用;净化后的池塘水与矿泉水、自来水中均含有水、可溶性的物质等物质,均属于混合物;蒸馏水中只含有水一种物质,属于纯净物.

(2)在电解水实验中,可观察到的现象有:正极的气体体积少,能使带火星的木条复燃,负极的气体体积多,能燃烧,而且体积多的是少的二倍.根据以上现象可推出正极产生的气体是氧气,负极产生的气体是氢气,还能进一步推出水由氢元素和氧元素组成.通过观察图可以发现:b接的是正极,b管气体少,所收集的气体是氧气,氧气的化学式为O2;氢气由氢元素组成,氧气由氧元素组成,在化学反应前后元素的种类不变,所以水由氢元素和氧元素组成。

(3)根据质量守恒定律进行分析解答.化学变化的实质是构成反应物分子的原子进行重新组合,在化学反应中原子种类不变,数目没有增减。

(4)可以根据分子在物理变化和化学变化中的变化进行分析、解答.蒸发水,水受热变成水蒸气,水分子之间的间隔增大,水分子本身没有发生变化,属于物理变化;而水分子通电后被分解为氧原子和氢原子,每两个氧原子构成一个氧分子,每两个氢原子构成一个氢分子,大量的氧分子聚集成为氧气,大量的氢分子聚集成为氢气,该变化属于化学变化。

判断题
阅读理解

阅读理解。

     If you walk slowly through downtown Helsinki (赫尔辛基) during the day, taking in the splendid 19th

century buildings, white boats and noise of passing trams (有轨电车), you will start to understand why it

is called a city of two colors: white and blue.

     The sea is always present in Helsinki. When you take a walk over the great open space of the central

square, you will hear seabirds screaming. When you take the tram, suddenly and unexpectedly, you are

faced with a calm, shining blue sea. You may notice that people in Helsinki do not rush about as in other

cities. Instead, they walk along the roads, politely letting other people by.

     A usual way to see Helsinki for the first time is to start out by boat. You will walk by the elderly women

selling fish and vegetables in the market square and find yourself in front of a beautiful park. You may enjoy

a pleasant walk in the park for a few hours and then take the tram. Trams are the perfect way to get around

in Helsinki. Watching the old houses, parks, theatres, churches, shops, restaurants and people in the streets,

you may have a slightly sad film feeling to it.

     The pale summer nights are another wonder in the city. Following the waterfront (滨水区) of the city

after sunset, you couldn't help stopping and listening to the sweet silence, interrupted only by the screaming

seabirds and leaving fishing boats.

     However, in some way Helsinki is also the most modern city in northern Europe. You will surely want to

visit the white Glass Palace, the modern art museum, and all those extremely popular cafes and design stores.

1. Helsinki is called a city of two colors mainly because of the colors of its ______.

A. 19th century buildings, boats and parks

B. 19th century buildings, boats and seabirds

C. old houses, parks and trams

D. old buildings, boats and the sea

2. The best way to see most of Helsinki is to go _____.

A. by boat

B. by bus

C. by tram

D. on foot

3. The 19th century buildings, the white Glass Palace, popular cafes and design shops in Helsinki all show that 

    Helsinki is _____.

A. both splendid and traditional

B. both quiet and noisy

C. both historical and modern

D. both old and new

4. This passage is most likely to be found in _____.

A. a story book

B. a geography textbook

C. a research report

D. a travel magazine