问题 选择题

下列物质熔沸点高低比较正确的是

A.SiO2<CO2

B.CCl4<CF4

C.NaCl<HCl

D.HF>HCl

答案

答案:D

题目分析:A、二氧化硅是原子晶体,二氧化碳是分子晶体,所以熔沸点SiO2>CO2,错误;B、CCl4、CF4都是分子晶体,前者的相对分子质量较大,所以熔沸点CCl4>CF4,错误;C、NaCl是离子晶体,HCl是分子晶体,所以熔沸点NaCl>HCl,错误;D HF、HCl都是分子晶体,但HF晶体中存在氢键,所以熔沸点HF>HCl,正确,答案选D。

填空题

You might think that hamburgers were invented in the United States, but that is not totally true. These (1) , or patties, actually came from Germany in the middle of the nineteenth century. They were brought to the United States by (2) who came from the city of Hamburg. That is why (3) was "hamburger steak".

However, people in other places (4) that they invented the hamburger. Perhaps we’ll never have a (5) . But there’s no question that the hamburger was a (6) . Why Perhaps because at that time, industry was growing and a kind of (7) food was needed for workers.

The hamburger became even more popular (8) when the first chain of fast food restaurants was started. This chain was called "White Castle". It served tiny hamburgers that were sold for only (9) . Then, in the 1930s there came the (10) where customers were served in their cars by waiters in uniform. And the hamburger was one of the most (11) .

By now, The hamburger was ready to (12) the world. And this happened with McDonald’s, which was actually a (13) at first. But by the early 1950s the hot dog was replaced by the hamburger. McDonald’s and other fast food restaurants (14) around the world throughout the rest of the twentieth century. McDonald’s alone has (15) for everyone person in the world.

The importance of the hamburger to (16) remains significant. About (17) of all sandwiches that are eaten are hamburgers. According to some sources, (18) of current workers in the United States had their first job at McDonald’s. But the face of the hamburger is changing (19) . Nowadays it is possible to buy a chicken burger, a turkey burger, (20) , or veggie burger.

13()

单项选择题