题干

家庭厨房实际上就是一个由众多物质构成的化学世界.其中,“油、盐、柴、米、酱、醋、茶”等都是化学物质.请你根据所学的化学知识,回答下列问题:
(1)目前,我市一些农村家庭所使用的燃料是沼气,沼气主要成分的化学式为____.
(2)永州人的主食是大米,其主要成分是淀粉,化学式为(C6H10O5)n,它是由____种元素所组成的.
(3)油脂、糖类、蛋白质等都是人所需的基础营养物质,其中作为人体备用的供能物质,且能溶解某些脂溶性维生素的是____.
(4)小梅家有食醋、纯碱和食盐的三种水溶液,其中一种溶液分别与另外两种溶液相混合,没有明显现象,则该溶液是____溶液(填化学式).

上一题 下一题 0.0难度 选择题 更新时间:2018-09-14 04:11:46

答案(点此获取答案解析)

CH4,三​,油脂,NaCl

同类题1

根据短文理解,选择正确答案。

    Five years ago, David Smith wore an expensive suit to work every day. “I was a clothes addict(有瘾的人),” he jokes. “I used to carry a fresh suit to work with me, so I could change if my clothes got wrinkled(有褶皱的).” Today David wears casual clothes (便装) to the office. He hardly ever wears a necktie. “I am working harder than ever.” David says, “and I need to feel comfortable.”

    More and more companies are allowing their office workers to wear casual clothes to work. In the United States, the change from formal to casual office wear has been gradual. In the early 1990s, many companies allowed their employees to wear casual clothes on Friday. This became known as “casual Friday”. “What started out as an extra one-day-a-week benefit for employees has really become an everyday thing.” said business consultant Maisly Jones.

    Why have so many companies started allowing their employees to wear casual clothes? “One reason is that it's easier for a company to attract new employees if it has a casual dress code.” “A lot of young people don't want to dress up for work,” says Owen Black, the owner of a software company, “so it's hard to hire people if you have a conservative (保守的) dress code.” Another reason is that people seem happier and more productive when they are wearing comfortable clothes. In a study conducted by Levi Company, 85 percent of employers said that they believe that casual dress improves employee morale (心境, 士气). Only 4 percent of employers said that casual dress has a negative influence on productivity. Supporters of casual office wear also argue that a casual dress code helps them save money. “Suits are expensive, if you have to wear one every day,” one person said. “For the same amount of money, you can buy a lot more casual clothes.”