问题 填空题

生活中的化学 ( 共10分,每空2分)

下面是俞觉敏同学写的作文《我的妈妈》中的一个片段:“妈妈能利用来自福安县的廉价葡萄自酿葡萄酒,这种家酿酒口感非常不错。葡萄酒酿好后不是直接装瓶,而是用纱布制成的袋子过滤后再装瓶,这样的目的是……”根据以上内容回答问题:

(1)葡萄酒过滤的目的是                                       。

(2)俞觉敏同学决定亲自动手做一做过滤实验,体验一下过滤的作用,她用浑浊的泥水进行过滤。她配制过滤器除了滤纸、铁架台外,还需要下列哪些仪器      (填代号)。

A      B     C  D

(3)过滤完后,她发现水仍很混浊其原因可能是                  

(4)过滤后的水澄清透明,因此俞觉敏认为过滤可以降低水的硬度。李明认为不对,因为降低水的硬度的方法是(写一种即可)            

(5)北方很多城市都缺水,严重影响到人们的生产和生活。我县森林覆盖率很高,山青水秀,为我们创造了一个美好的生活环境。为了使我们的天更蓝水更清,你的做法是(任写一点)               

答案

(1)葡萄酒过滤的目的是 除去葡萄酒中的葡萄皮、籽等不溶性事杂质。

(2)BCD

(3)滤纸破了(或液面高滤纸边缘) 。

(4) 蒸馏(或 煮沸)。

(5)不焚烧垃圾(或合理使用化肥和农药)只要能答到保护空气和水体的答案均可。

题目分析:(1)由于自制的葡萄酒中常混有葡萄皮、葡萄籽等不溶性的杂质,葡萄酒过滤的目的就是要除去葡萄酒中的葡萄皮、籽等不溶性杂质。

(2)根据过滤的操作及仪器的名称和用途分析,配制过滤器,除了滤纸、铁架台外,还需要漏斗、烧杯、玻璃棒等,故选BCD;

(3)过滤后,仍混浊的原因可能是滤纸破了或液面高于滤纸的边缘,致使一些不溶物直接进入滤液,而使滤液浑浊;

(4)过滤可将不溶于液体的固体从液体中分离出来,而硬水和软水相比,主要是含有较多的可溶性的钙、镁化合物,而过滤不能除去可溶性的钙、镁化合物;硬水软化,就是设法除去硬水中的钙、镁化合物,使之软化成软水,工业上和科学实验中软化硬水的方法是采用蒸馏的方法,就可降低水的硬度,使之软化,而生活中则通过煮沸的方法来实现。

(5)根据保护环境常见的措施分析,为了使我们的天更蓝水更清,应不焚烧垃圾、合理使用化肥和农药等。

点评:本题主要考查的是过滤的操作,解答本题要熟练掌握过滤操作的原理,只有这样才能对过滤中出现的问题做出正确的判断。

问答题 简答题
单项选择题

The human Y chromosome—the DNA chunk that makes a man a man—has lost so many genes over evolutionary time that some scientists have suspected it might disappear in 10 million years. But a new study says it’ll stick around.
Researchers found no sign of gene loss over the past 6 million years, suggesting the chromosome is "doing a pretty good job of maintaining itself," said researcher David Page of the Whitehead Institute for Biomedical Research in Cambridge, Mass.
That agrees with prior mathematical calculations that suggested the rate of gene loss would slow as the chromosome evolved, Page and study co-authors note in Thursday’s issue of the journal Nature. And, they say, it clashes with what Page called the "imminent demise" idea that says the Y chromosome is doomed to extinction.
The Y appeared 300 million years ago and has since eroded into a dinky chromosome, because it lacks the mechanism other chromosomes have to get rid of damaged DNA. So mutations have disabled hundreds of its original genes, causing them to be shed as useless. The Y now contains only 27 genes or families of virtually identical genes.
In 2003, Page reported that the modern-day Y has an unusual mechanism to fix about half of its genes and protect them from disappearing. But he said some scientists disagreed with his conclusion. The new paper focuses on a region of the Y chromosome where genes can’t be fixed that way.
Researchers compared the human and chimpanzee versions of this region. Humans and chimps have been evolving separately for about 6 million years, so scientists reasoned that the comparisons would reveal genes that have become disabled in one species or the other during that time.
They found five such genes on the chimp chromosome, but none on the human chromosome, an imbalance Page called surprising. "It looks like there has been little if any gene loss in our own species lineage in the last 6 million years," Page said. That contradicts the idea that the human Y chromosome has continued to lose genes so fast it’ll disappear in 10 million years, he said. "I think we can with confidence dismiss … the ’imminent demise’ theory," Page said.
Jennifer A. Marshall Graves of the Australian National University in Canberra, a gene researcher who argues for eventual extinction of the Y chromosome, called Page’s work "beautiful" but said it didn’t shake her conviction that the Y is doomed.
The only real question is when, not if, the Y chromosome disappears, she said. "It could be a lot shorter than 10 million years, but it could be a lot longer," she said.
The Y chromosome has already disappeared in some other animals, and "there’s no reason to expect it can’t happen to humans," she said. If it happened in people, some other chromosome would probably take over the sex-determining role of the Y, she said.

Page seems to believe that
[A] the gene loss of Y chromosome is sure and fast.
[B] the gene loss of Y chromosome is quite slow.
[C] the Y chromosome is facing "imminent demise".
[D] the Y chromosome will be replaced by a new one.