题目

下列现象可用质量守恒定律解释的是 A．木炭在空气中燃烧后化为灰烬，灰烬的质量比原来木炭的质量要小得多 B． 1L 氢气和 1L 氧气完全反应生成 2L 水 C． 5g 食盐溶于 95g 水中后，所得的食盐水的总质量为 100g D． 10g 水在受热的条件下变成了 10g 的水蒸气 答案：A【解析】 【详解】 A、木炭在空气中燃烧后化为灰烬，木炭中碳元素结合氧元素生成二氧化碳逸出，所以灰烬的质量比原来木炭的质量要小得多，故 A 正确； B、化学反应前后，参与反应的反应物和生成物的质量遵循质量守恒定律，但是体积不一定守恒，故 B 错误； C、质量守恒用于解释化学反应，A study involving 8,500 teenagers from all social backgrounds found that most of them are ignorant when it comes to money. The findings, the first in a series of reports from NatWest that has started a five-year research project into teenagers and money, are particularly worrying as this generation of young people is likely to be burdened with greater debts than any before. University tuition fees are currently capped at £3,000 annually, but this will be reviewed next year and the Government is under enormous pressure to raise the ceiling. In the research, the teenagers were presented with the terms of four different loans but 76 per cent failed to identify the cheapest. The young people also predicted that they would be earning on average £31.000 by the age of 25, although the average salary for those aged 22 to 29 is just £17,815. The teenagers expected to be in debt when they finished university or training, although half said that they assumed the debts would be less than £10.000. Average debts for graduates are £12,363. Stephen Moir, head of community investment at the Royal Bank of Scotland Group which owns NatWest, said. "The more exposed young people are to financial issues, and the younger they become aware of them, the more likely they are to become responsible, forward-planning adults who manage their finances confidently and effectively." Ministers are deeply concerned about the financial pressures on teenagers and young people because of student loans and rising housing costs. They have just introduced new lessons in how to manage debts. Nikki Fairweather, aged 15, from St Helens, said that she had benefited from lessons on personal finance, but admitted that she still had a lot to learn about money. 1. Which of the following can be found from the five-year research project? A. Students understand personal finances differently.  B. University tuition fees in England have been rising. C. Teenagers tend to overestimate their future earnings. D. The students' payback ability has become a major issue. 2. The phrase "to raise the ceiling" in paragraph 2 probably means "______". A. to raise the student loans                B. to improve the school facilities C. to increase the upper limit of the tuition  D. to lift the school building roofs 3. According to Stephen Moir, students _______. A. are too young to be exposed to financial issues B. should learn to manage their finances well C. should maintain a positive attitude when facing loans D. benefit a lot from lessons on personal finance 4. What can we learn from the passage? A. Many British teenagers do not know money matters well B. Teenagers in Britain are heavily burdened with debts. C. Financial planning is a required course at college. D. Young people should become responsible adults.