Air is a colorless gas, which can neither be seen nor touched. In class, we thought of ways to observe air flow: (1) (2) (3) (4).

Soviet educator Svilov said: "Humor is the most important first assistant of educators." At that time, the city's teaching and research staff came to my class, and I happened to be talking about the second class of air, which was a valuable resource. Because there are still pure substances and mixtures left in the last class, Teacher Mao commented that "the water is not thorough enough". In fact, I know very well that I deliberately didn't say it too bluntly. When I say water, pure water and distilled water alone, I mean pure things, and when any modifiers are added in front of water, I mean mixtures. Because the pure water used for teaching AIDS last year was pure, I didn't mean pure when there was a modifier in front of the water. I want to look again and come to a conclusion. In addition, one thing I should change is that I don't trust students in class. It may be better if the class is introduced as follows: animation (space navigation, using air as raw material to help complete the task) Students can read the future Shenzhou by themselves and conduct interstellar navigation. Can you make suggestions with your knowledge about air? 1. Support fuel combustion and gas use. 2. In order to provide breathing for astronauts, gas can be used. Astronauts need sleep, and they can use gas. 4. The laser that hits the meteorite can use gas. 5. The welding spacecraft needs gas to support combustion and needs to be used as welding protective gas. 6. The alien base can store food and use gas. Can you draw a conclusion about the use of oxygen from the above question and answer? Students here may say that oxygen can breathe and burn? At this time, you can say oxygen breathing. What do people breathe? Oxygen will burn. If you are angry that day, maybe the fire in your stomach will run out. You can use your mouth as fuel when cooking at home. Students will learn knowledge through laughter. The purpose of oxygen is to provide breathing and support combustion. About the properties and uses of nitrogen: First, make a table about the melting point of nitrogen, and get the physical properties of nitrogen: low melting point. Let the students reach out and smell the air, and sum up the physical properties of nitrogen: colorless, odorless, insoluble in water and low melting point gas. Chemical properties: neither burning nor supporting burning. Chemically inactive. It is even more interesting about rare gases: looking back at the composition of air, we know that there is another inert gas in the air, which is a rare gas. It is great to get physical and chemical properties and get the use of rare gases through a video. Fully stimulate students' curiosity in learning. At this time, students should pay attention to some polluted pictures to attract students' attention, thus causing the topic of air protection and leading to three major environmental problems, the harm of air pollution and preventive measures. There are two sources of air pollution: harmful gases and dust. More than half of carbon monoxide in harmful gases comes from automobile exhaust. Here is a joke: a student asked the teacher, "Teacher, a scientist once said that more than half of carbon monoxide comes from cow fart". The students will burst into laughter when they hear this. At the end of the course, students are left with two questions: 1. Protecting the environment should start with us and think about what you should and can do for our home air. Second, one day you may be the mayor or the governor, and you can do more than you do now. How will you protect and beautify your home air? I feel that if this class follows this train of thought, there may be another gain. Thinking about the gains and losses after a class, getting students' affirmation and negation, seriously thinking and carefully designing this class may be more conducive to their own growth, better improving themselves, better improving the classroom, better achieving more students and better attracting students' curiosity and confidence.

Air is a colorless gas, which is invisible and intangible. In class, we thought of ways to observe the airflow: (1) (2) (3) (4). It's too difficult. I tried very hard to answer. Give me a satisfactory answer.