题干

学校化学兴趣小组知道二氧化锰能做过氧化氢分解的催化剂后,在想探究其他一些物质如氧化铝是否也可做过氧化氢的催化剂。请你一起参与他们的探究过程,并填写下列空白。

【问题】氧化铝能不能做过氧化氢分解的催化剂?

【猜想】氧化铝能做过氧化氢分解的催化剂

【实验验证】


实验步骤

实验现象

实验结论

实验一

____

木条不复燃

常温下过氧化氢溶液不分解

实验二

在装有过氧化氢溶液的试管中加入少量氧化铝,然后将带火星的木条伸入试管中

木条复燃

____

【结论】氧化铝能加快过氧化氢的分解速率,故氧化铝能做过氧化氢分解的催化剂

【讨论与反思】经过讨论,有的同学认为只有上述两个证据,不能证明氧化铝能作过氧化氢分解的催化剂,还要补充一个探究实验:

实验三:【实验目的】探究____.

【实验步骤】①准确称量氧化铝(少量)的质量;②完成实验二③待反应结束,将实验而试管里的物质进行过滤,洗涤,________;对比反应前后氧化铝的质量。

【讨论】如果氧化铝在反应前后质量不变,则说明氧化铝可以做过氧化氢分解的催化剂。

但小华认为,要证明猜想,上述三个实验还不足够,还需要再增加一个探究实验____.请简述操作和现象:①____.②____

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同类题5

任务型阅读

    Age has its privileges in America, and one of the more prominent of them is the senior citizen discount. Anyone who has reached a certain age — in some cases as low as 55 — is automatically entitled to dazzling array of price reductions at nearly every level of commercial life. Eligibility is determined not by one's need but by the date on one's birth certificate. Practically unheard of a generation ago, the discounts have become a routine part of many businesses — as common as color televisions in motel rooms and free coffee on airliners.

    People with gray hair often are given the discounts without even asking for them; yet, millions of Americans above age 60 are healthy and solvent(有支付能力的). Businesses that would never dare offer discounts to college students or anyone under 30 freely offer them to older Americans. The practice is acceptable because of the widespread belief that “elderly” and “needy” are synonymous (同义的). Perhaps that once was true, but today elderly Americans as a group have a lower poverty rate than the rest of the population. To be sure, there is economic diversity within the elderly, and many older Americans are poor. But most of them aren't.

    It is impossible to determine the impact of the discounts on individual companies. For many firms, they are a stimulus to revenue. But in other cases the discounts are given at the expense, directly or indirectly, of younger Americans. Moreover, they are a direct irritant in what some politicians and scholars see as a coming conflict between the generations.

    Generational tensions are being fueled by continuing debate over Social Security benefits, which mostly involve a transfer of resources from the young to the old. Employment is another sore point. Buoyed (支持) by laws and court decisions, more and more older Americans are declining the retirement dinner in favor of staying on the job — thereby lessening employment and promotion opportunities for younger workers.

    Far from a kind of charity they once were, senior citizen discounts have become a formidable economic privilege to a group with millions of members who don't need them.

    It no longer makes sense to treat the elderly as a single group whose economic needs deserve priority over those of others. Senior citizen discounts only enhance the myth that older people can't take care of themselves and need special treatment; and they threaten the creation of a new myth, that the elderly are ungrateful and taking for themselves at the expense of children and other age groups. Senior citizen discounts are the essence of the very thing older Americans are fighting against — discrimination by age.

Outline

Details

Introduction

Age determines whether an American can be given a discount, which is a common ____in American business life today.

Origin of senior citizen discount

●Since the senior citizens are often treated as people who are in ____, they are given such priority.


____

situation

●The situation has changed a lot where the majority of the elderly are not poor at all.

●Younger Americans were at a/an ____ directly or indirectly due to the discounts given to the elderly, thus leading to conflicts between generations.

●The number of older Americans ____ to work rather than retire is on the increase, which means  ____ opportunities for young workers.

●It is no longer a kind of charity because millions of senior citizens don't need the priority ____.




Conclusion

It's unwise to offer discount priority to the elderly.

●It will mislead people to think they are unable to ____ to themselves.

●People may think that they are ungrateful and they're hurting the ____ of other age groups.

●Actually senior citizen discounts, to some extent, ____against their age.