图中(1)是小明同学利用老师提供的实验器材组装的做“观察水的沸腾”的实验装置.

题型:填空题

问题:

图中(1)是小明同学利用老师提供的实验器材组装的做“观察水的沸腾”的实验装置.

(1)小明同学从冰箱内取出了50cm3小冰粒来做这次实验,每隔一定时间记录一次温度计的示数,作出下列图象.已知冰的密度为900kg/m3.酒精灯每分钟燃烧酒精0.0028kg,酒精的热值为3.0×107J/kg,对实验过程中的水而言,酒精灯的效率为______.

(2)图(3)是小明根据实验所得数据作出的温度随时间变化的图象,由图中提供的信息可知:小冰粒熔化过程经历了______min.水沸腾过程中温度保持不变,内能______(选填“变小”、“不变”或“变大”).

(3)根据所画的图象分析可知当时的气压______(选填“大于”、“小于”或“等于”)1标准大气压.

(4)小明发现自己组的水比邻组的水后沸腾,水后沸腾的原因可能是______(写出一种即可).

考点:沸腾及沸腾的特点
题型:填空题

为测定石灰石中碳酸钙的纯度,取一定质量的石灰石(所含杂质不溶于水,不与酸反应,高温也不分解), 高温煅烧一段时间后得到 78g 固体, 该固体与 400g 溶质的质量分数为 14.6%的稀盐酸恰好完全反应后,过滤得到20g滤渣,则石灰石中碳酸钙的质量分数为

A.74.4%

B.80%

C. 83.8%

D.92.6%

题型:填空题

如图所示,物体G在竖直向上的拉力F的作用下,匀速上升0.2m。已知G=18N,F=10N。这一过程中,不能得到的结论是

A.绳子自由端上升0.4m

B.拉力F做功4J

C.动滑轮重为2N

D.该动滑轮的机械效率为90%

题型:填空题

某国有企业2002年度总收入为3400万元,成本、费用支出总额为1900万元,该企业2002年度应缴纳企业所得税税额是( )万元。

A.405

B.495

C.450

D.270

题型:填空题

American Museum of Natural History is one of the largest natural and historic museums in the world and one of the main natural history research and education centres in the United States, set up in 1869 and located in the west of the Central Park, Manhattan District, New York. It (1) 7 hectares in its total area, (2) classical types of buildings. The (3) of ancient creatures and humanity is (4) the first place of all the museums in the world, (5) the representative samples from South America, Africa, Europe, Asia and Australia were collected, besides those from the (6) country, the United States.In the museum, there are five kinds of exhibits, including astronomy, mineralogy, human history, and animals in the (7) times and those in modern times. There are thirty-eight exhibition halls with different (8) from 500 to 1,500 square metres. Besides these, there is a Roosevelt Memorial Hall in (9) of President Roosevelt who supported the (10) of the museum, which is also used to have a special exhibition, showing the new important (11) on natural sciences and (12) affairs and social problems, and special topics connected closely with the life of the citizens. Besides this, it is also used for avocation (13) to have all kinds of scientific activities in the laboratories, centres of natural science and centres for citizens. There are more than 10 (14) research departments mainly(15) for collection of samples, research and work of publication.In the museum, there are (16) and sub-libraries of Aulspond ancient amniote, with about 300 thousand books and magazines (17) natural history, many of(18) are very valuable monographs for the first edition. It has published many expert books and magazines, and a large number of propaganda materials, (19) which are the two magazines, Natural History and Members of Museum that have the biggest (20) of their magazines.

6()

A.wholesome

B.feasible

C.native

D.weird

题型:填空题

下述哪项是乳腺癌出现表面皮肤凹陷的机制()

A.癌肿侵入乳腺管使其收缩

B.癌细胞堵塞 * * 皮下淋巴管

C.癌细胞浸润大片皮肤

D.癌肿侵犯Cooper韧带使其收缩

E.以上都不是

更多题库