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铅(Pb)是一种化学性质比较活泼的金属,纯净的铅外观和铁相似。相同体积的铅和铁比较,铅比铁重,把纯铅放置在空气中,过一段时间表面会形成氧化膜而变得很暗,用铅在纸上划,会留下一道黑色痕迹,在古代,人们用铅做笔,铅笔的名字便由此而来。把铅投入到稀盐酸中,溶液中会出现气泡。根据以上信息归纳总结,并回答下列问题:(已知铅在化合物中最常见的化合价为+2)

(1)上文关于铅的物理性质有____________;化学性质有______________。(各答出一点即可)

(2)写出盐酸和铅反应的化学方程式_______________。

答案

(1)银白色、固体、密度比铁大、质软;能与空气中的氧气反应、能与盐酸反应

(2)Pb+2HCl==PbCl2+H2

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How to Do Well in Exams

Do not underestimate the power of revision in the days and hours before and examination. The closer you are to the exam, the more chance you have of storing and retaining crucial information. But do not overdo it.  小题1:  An effective daily routine can help you through an exam period, so in the days leading up to your first exam, get into the habit of being up and ready to work by game. It can be a shock to the system after months of working to your own timetable to be mentally alert at that time if you have not prepared for it. 

On the day of the exam, have a good breakfast, pack two of everything you need(pens, pencils, erasers, etc.), then make you way to the examination hall in good time.   小题2:  

Once in your seat, simply pause for a few seconds and collect your thoughts. Close you eyes and take in a few slow, deep breaths to help you relax. When you turn over the test paper, spend a short period reading through all the instructions and questions, paying particular attention to key verbs such as “discuss”, “compare” and “evaluate”.   小题3:  It is wise always to allow for 10 minutes at the end of the exam to give yourself time to go back over your answers. Once you have selected the questions you wish to tackle, begin by attempting the one you think is your strongest. It will give you more confidence when you see a well-answered question down on paper. Also remember to write clearly, and do not be afraid to express the unexpected: after all, examiners can get very bored marking stereotypical answers.

 小题4:  If you do need something else to focus on to help collect your thoughts, choose a fixture in the room, such as the ceiling or anything else that will not allow you to be distracted.

Finally, once you have finished, never hang around outside afterwards to attend the discussion by other students.   小题5: 

A.Do not arrive too early, though, as other people’s anxiety can by contagious, and you may suffer from undue panic

B.Try not to be tempted to look at those around you, or at the clock

C.When you get home, read the examination paper through and look up all the words you didn’t understand

D.Sleep, exercise and relaxation are all just as importantE. Map out a quick plan of points you wish to make and how much time you should spend on each question.

F. Go and have a well-earned rest, then prepare for your next exam.

G. Hurry and prepare for your next exam

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