Please think about what characteristics of a successful scientist are.
How are the words and phrases related to each other?
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3. Please find out the six elements of the passage.
Who: Alexander Fleming
When: in 1928
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What: Penicillin
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In the
early 1900s: used a chemical
treatment in his clinic
In World War I: invented many new ways to treat the wounded
After the war: began searching for the chemical
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At that time: other scientists showed no interest
Until World war II: The importance of penicillin was fully recognized
In 1945: Fleming was rewarded Nobel Prize for his great discovery
2. What do you pay attention to when you read it?
This is a narration. When we read a narration, we should six elements of a narration:
Who, when, where, what, why and how.
Please scan the passage to answer the questions.
1. What type of writing literary form does it belong to?
Please skim the passage to find out the topic sentence of each paragraph or sum up the general idea of it in your own words.
Para1. The discovery is a story of hard work and a happy accident.
Para2. Fleming invented many new ways to treat the wounded in World War I.
Para3. Fleming discovered a mould that could kill bacteria by accident.
Para4. Despite other scientists’ lack of interest, Fleming kept trying to develop the chemical so that it would be safe and effective.
Para5. The importance of Fleming’s discovery wasn’t fully recognized until World War II..
General idea:
This passage tells us how penicillin was discovered. The discovery of it not only take hard work but also needs many good characteristics of a scientist, such as devotion to duty, full of confidence and so on.
The Chinese government has been making great efforts to fight against poverty and improve health care. At the same time, there are a quite few persons who also make great contributions to health care. Do you know what kinds of person they are? They must be doctors, nurses, chemists, and chemical scientists. For example, in 1928, a young Scottish scientist discovered a chemical that was very effective in curing infections. Do you know who he is? What does he call the chemical? If you want to find out the answers to the questions, please read the passage The Little Mould That Could at Page79.
Teaching methods:
Skimming method; Scanning method; Introductive method
Teaching aids:
A blackboard; A recorder; Some chalks
Teaching steps:
II Find out what characteristics helped Alexander Fleming discover Penicillin.
Teaching difficult points:
Teaching difficult points:
2. 原电池的原理
负极----较活泼的金属--- 电子------发生 反应
正极----较不活泼的金属---- 电子----发生 反应
试题枚举
[例1]下列叙述中正确的是
A.构成原电池正极和负极的材料必须是两种金属。
B.由铜、锌作电极与硫酸铜溶液组成的原电池中铜是负极。
C.马口铁(镀锡铁)破损时与电解质溶液接触锡先被腐蚀。
D.铜锌原电池工作时,若有13克锌被溶解,电路中就有0.4mol电子通过。
解析: 两种活动性不同的金属与电解质溶液能够组成原电池,但不能因此说构成原电池电极的材料一定都是金属,例如锌和石墨电极也能跟电解质溶液组成原电池。在原电池中,活动金属中的电子流向不活动的电极,因此活动金属是负极。镀锡铁表皮破损后与电解质溶液组成原电池,铁较锡活泼,铁先失电子被腐蚀。铜锌原电池工作时,锌负极失电子,电极反应为Zn –2e==Zn2+,1molZn失去2mol电子,0.2mol锌(质量为13克)被溶解电路中有0.4mol电子通过。故选D。
答案:D
[例2]把A、B、C、D四块金属泡在稀H2SO4中,用导线两两相连可以组成各种原电池。若A、B相连时,A为负极;C、D相连,D上有气泡逸出;A、C相连时A极减轻;B、D相连,B为正极。则四种金属的活泼性顺序由大到小排列为
A.A>B>C>D B.A>C>B>D C.A>C>D>B D.B>D>C>A
解析:金属组成原电池,相对活泼金属失去电子作负极,相对不活泼金属作正极。负极被氧化质量减轻,正极上发生还原反应,有物质析出,由题意得活泼性 A>B、A>C、C>D 、D>B,故正确答案为B。
答案:B
[例3]电子计算机所用钮扣电池的两极材料为锌和氧化银,电解质溶液为KOH溶液,其电极反应是: Zn + 2 OH- -2e=ZnO + H2O Ag2O +H2O + 2e=2Ag +2 OH-
下列判断正确的是
A.锌为正极,Ag2O为负极。 B.锌为负极,Ag2O为正极。
C.原电池工作时,负极区溶液PH减小。 D.原电池工作时,负极区溶液PH增大。
解析:本题考查原电池和PH的概念。
原电池中失去电子的极为负极,所以锌为负极,Ag2O为正极。B是正确答案。因为 Zn + 2 OH- -2e=ZnO + H2O ,负极区域溶液中[OH-] 不断减少,故PH减小,所以C也正确。故选B、C。
答案:BC
[变式]化学电池在通讯、交通及日常生活中有着广泛的应用。
(1)目前常用的镍(Ni)镉(Cd)电池,其电池总反应可以表示为:Cd+2NiO(OH)+2H2O
2Ni(OH)2+Cd(OH)2已知Ni(OH)2和Cd(OH)2均难溶于水但能溶于酸,
以下说法中正确的是
①以上反应是可逆反应 ②以上反应不是可逆反应
③充电时化学能转变为电能 ④放电时化学能转变为电能
A.①③ B.②④ C.①④ D.②③
(2).废弃的镍镉电池已成为重要的环境污染物,有资料表明一节废镍镉电池可以使一平方米面积的耕地失去使用价值。在酸性土壤中这种污染尤为严重。这是因为
。
(3).另一种常用的电池是锂电池(锂是一种碱金属元素,其相对原子质量为7),由于它的比容量(单位质量电极材料所能转换的电量)特别大而广泛应用于心脏起搏器,一般使用时间可长达十年。它的负极用金属锂制成,电池总反应可表示为:Li+MnO2→LiMnO2试回答:锂电池比容量特别大的原因是 。锂电池中的电解质溶液需用非水溶剂配制,为什么这种电池不能使用电解质的水溶液?请用化学方程式表示其原因 。
答案:(1)B (2)Ni(OH)2和Cd(OH)2能溶于酸性溶液。
(3)锂的摩尔质量小;2Li+2H2O→2LiOH+H2↑
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