问题
选择题
物质在不断的运动变化，属于物理变化的是（ ）
A．冰雪融化
B．大米酿酒
C．木炭燃烧
D．铁钉生锈
答案
A、冰雪融化的过程中只是状态发生改变，没有新物质生成，属于物理变化．
B、大米酿酒的过程中有新物质酒精等生成，属于化学变化．
C、木炭燃烧的过程中有新物质二氧化碳等生成，化学变化．
D、铁钉生锈的过程中有新物质铁锈生成，属于化学变化．
故选A．
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物质在不断的运动变化，属于物理变化的是（ ）
A．冰雪融化
B．大米酿酒
C．木炭燃烧
D．铁钉生锈
A、冰雪融化的过程中只是状态发生改变，没有新物质生成，属于物理变化．
B、大米酿酒的过程中有新物质酒精等生成，属于化学变化．
C、木炭燃烧的过程中有新物质二氧化碳等生成，化学变化．
D、铁钉生锈的过程中有新物质铁锈生成，属于化学变化．
故选A．
注意：每个空格只填一个单词。 We all need physical exercise. Exercise uses up food we eat and keeps the body full of energy. It works your muscles and makes your heart work hard so as to send blood to your muscles. So, exercise makes your heart and muscles strong. Exercise also makes you feel refreshed. If you exercise a couple of times a week, you will stay happy and healthy. Some Western countries, such as the United States, have problems with exercise. In the US, many people don’t have enough exercise because it is hard for them. People have to work from dawn till dusk, so they don’t have time to take exercise. They work in office buildings sitting in chairs all day long in front of computers. They cannot get much exercise sitting at desk passively. Some Westerners can get exercise walking from their homes to work. However, the majority of people cannot do this. It is too far from their homes to their offices. They have no choice but to drive to work. In fact, some have to drive one or two hours to their offices. This is unfavourable in two ways. First, these people don’t have a chance to exercise because they are sitting in their cars for two to four hours each day. Second, driving is challenging especially in rush hours and calls for too much attention. It makes a person worn out. So, when these people arrive home at night, they don’t have the desire to take exercise after work. Today, many people in the West are overweight, which causes health problems for them. Doctors say exercise can help people both lose weight and improve their health. So many people are trying to get more exercise. But it takes time to change, and when people don’t see a difference right away, they will lose heart and stop exercising.
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