The following explains how I strengthen concept teaching and experimental inquiry teaching in the teaching according to the pressure of concept teaching. Solid, liquid and gas can all produce pressure, which is difficult for junior high school students to learn, because the knowledge of pressure is abstract, especially the knowledge of liquid pressure needs strong abstract thinking ability; The knowledge in this unit needs to comprehensively apply the concepts, density and balance of two forces. Explaining related phenomena and answering questions require certain analytical and expressive skills. Moreover, the pressure measurement and measurement methods of solid, liquid and gas are different, which is an important concept in middle school physics teaching. It belongs to the interaction between substances and has strong regularity. It is closely related to life and production. In order to let students deeply understand the related knowledge of stress, I have done the following in teaching. First, compare and summarize, strengthen the teaching of physical concepts 1. The difference and connection between pressure and gravity. In explaining the concept of pressure, in order to let students distinguish between pressure and gravity, I adopted the comparative teaching method. Let the students realize that pressure and gravity are two different forces, and the pressure is not necessarily caused by the gravity of the object, but when the object is resting on the horizontal support surface, the pressure of the object on the support surface is equal to the gravity of the object, and it is illustrated by drawing a schematic diagram of the force. For example, push the thumbtack against the wall by hand, and the wall is under the pressure of the thumbtack tip, and the pressure direction is perpendicular to the wall surface. The force is exerted by pushing the needle, and the force is exerted by the wall, which has nothing to do with the gravity of pushing the needle. It can also be illustrated by a list, for example, taking the pressure generated by a block of wood with mass m placed on an inclined plane as an example to illustrate the difference between these two forces. The force at the point where an object is subjected to the force of the object. The essence of force is gravity. The center of gravity of the earth block is vertically downward. Milligram gravity pressure. The inclined plane of the wood block is perpendicular to the inclined plane and downward less than the elastic force of mg. Therefore, the fact that the pressure exerted by an object on a horizontal desktop is equal to the weight of the object itself only shows that the pressure is equal to the gravity of the object in numerical value and in the same direction, which cannot be confused. After studying the pressure of solid, liquid and gas, students often confuse the application of formulas P=ρgh and P=F/S, and don't understand their respective application ranges. Therefore, analyzing the differences and connections between them with students will help students understand the formulas and principles, and thus solve practical problems correctly. (1) The pressure in the formula P=ρgh is the pressure generated by the liquid due to its own gravity, excluding the external pressure on the liquid. So this formula is the liquid pressure formula. According to the formula, the internal pressure of liquid is only related to the density and depth of liquid, and has nothing to do with the volume and quality of liquid. Because liquid has fluidity and can transmit pressure, the law of liquid pressure is different from that of solid pressure, so we must consider their own special reasons when analyzing problems. We can use the research methods of list comparison and analogy analysis to analyze the following problems. Guide students to learn the methods of linking knowledge and analyzing problems before and after. If a container with a certain amount of liquid is placed on a horizontal table, is the pressure and pressure generated by the container on the table equal to the pressure and pressure generated by the liquid at the bottom of the container (excluding the weight of the container)? Please look at the following table: the magnitude of the cause pressure of the target. For horizontal desktop containers and liquids, the pressure is equal to the total weight of the container and water, regardless of the stress area. Calculation method: F=G is related to the gravity of the container and water, and to the stress area. Calculation method: When p=F/S exerts gravity on the liquid at the bottom of the container, the pressure that the liquid can transmit is not necessarily equal to the weight of the liquid, which is related to the pressure of the liquid and the bottom area. Column: F=G, upper small and lower large: f > g, upper small and lower small: f < g Calculation method: F=pS=ρghS is related to the density and depth of the liquid, but has nothing to do with the shape and bottom area of the container. Calculation method: p=ρgh As can be seen from the above table, when calculating solid pressure and pressure, the pressure is generally calculated first and then the pressure, while when calculating liquid pressure and pressure, the pressure is generally calculated first and then the pressure. Knowing this solution order, coupled with the understanding of the meaning of the formula, will greatly reduce the probability of making mistakes in this kind of problem in the future. (2) the scope of application of the formula P=ρgh This formula is only suitable for calculating the pressure of static liquid, but not for calculating the pressure of solid. Although sometimes the pressure produced by solids is exactly equal to ρgh. For example, if a cuboid or cylindrical iron block with uniform density and height h is placed on a horizontal desktop, the pressure on the desktop is P=F/S=ρgV/S=ρghS/S=ρgh, but this is only a special case, and it cannot be considered that the pressure on the support caused by the solid's own strategy can be calculated by p=ρgh. (3) Relationship between Formula P=ρgh and P=F/S Formula P=F/S is the definition and determination of pressure. Whether it is solid, liquid or gas, it is applicable and a commonly used formula. And P=ρgh is derived from P=F/S according to the specific situation of liquid, which is only suitable for calculating the pressure of liquid. Can the formula P=ρgh be used to calculate atmospheric pressure? Because the liquid is difficult to be compressed and its volume is not easy to change, the density of the liquid in the container is the same from top to bottom. Because gas can be compressed, its volume can be easily changed. When the external pressure of a certain mass of gas increases, its volume will decrease and the gas density will increase. Therefore, the density of air is different at different heights of the atmosphere. The air density near the ground is relatively high, and the higher it is, the smaller it is. Because the density of air in the atmosphere is uneven, it is impossible to calculate the atmospheric pressure at a certain height in the atmosphere with p=ρgh. Through the above analysis and comparison, students have a deep understanding of the pressure of solid, liquid and gas, and can solve practical problems according to principles and formulas when analyzing problems, and also cultivate students' skills and methods of learning physics knowledge. Second, strengthen experiments and inquiry, and attach importance to the teaching of scientific methods. I try my best to arrange inquiry learning activities in teaching. Although the school lacks equipment, it is difficult to carry out group experiments, but I will try my best to make use of the equipment around me to do many demonstration experiments for students, and at the same time improve the experiments, and try my best to let students do some experimental exploration with the equipment around me. When doing demonstration experiments, the experimental process still follows the link of experimental inquiry, and most procedures require students to complete them together. In experimental teaching, my teaching procedure is: asking questions-guessing-designing experiments-conducting experiments-inductive analysis-drawing conclusions-communicating and evaluating-application and popularization. For example, in the experiment of exploring "What factors are related to the role of stress", first, by observing various phenomena related to stress in life, we can understand what pressure is and know that pressure can have a certain effect, and then let students guess. "Guess" is a scientific research method. Conjecture plays an important role in the learning process of scientific inquiry. It is the most active part of body wisdom, so I usually attach great importance to the teaching of this link. Let students' thinking spread out first, and fully develop their innovative thinking, but in order to prevent students from guessing at will, students should also give reasons for guessing, so as to get rid of the false and keep the true, and get rid of the rough and get the essence, so as to make the inquiry activities go smoothly. There are many factors that make students guess, such as pressure, gravity, mass, stress area, volume and so on. Then I guide students to analyze and screen, merge and summarize, and finally come to the conclusion that the role of pressure may be related to the size of pressure and the size of stress area. Ask students to design experiments after guessing, and emphasize the scientific method of "control variable method" to students before designing experiments. "Control variable method" is a scientific method commonly used in junior high school physics inquiry. It is also the focus of our teaching. When a physical quantity is related to several factors, we usually study the relationship between the physical quantity and each factor separately, and then draw a conclusion through comprehensive analysis. In this way, when studying the relationship between physical quantity and one of the factors, we must artificially control other factors to keep them unchanged, so as to observe and study the relationship between physical quantity and this factor. This is the "control variable method". With this scientific thinking, it is not too difficult for students to design experiments. That is to say, first keep the pressure constant, change the pressure, and study the relationship between the function of pressure and pressure, then keep the pressure constant, change the stress area, and study the relationship between the function of pressure and the stress area. How to observe the effect of stress? Force is an invisible and intangible physical quantity. How to show the effect of stress? This involves the teaching of a scientific method "transformation method". The so-called "transformation method" mainly refers to transforming invisible and difficult-to-see phenomena into visible and easy-to-see phenomena on the premise of ensuring the same effect; Turn unfamiliar complex problems into familiar simple problems; A method of converting physical quantities that are difficult to measure or measure into physical quantities that can be measured or measured. To show the effect of pressure, that is, to make the effect of pressure more obvious, how should we choose the pressed object (bracket)? Students will suddenly think of choosing softer surfaces as supporting surfaces, such as sand, sponge, soft foam, flour and even muscles. After all the work in the early stage of the experiment is completed, you can choose the appropriate equipment for the experiment. On the basis of experimental observation, you can naturally draw experimental conclusions smoothly. Third, pay attention to expanding applications and guide students to innovate. After the conclusion of the experiment, let the students discuss and communicate, and point out the problems existing in the experiment. What can be improved? For example, after the above experiment, a student suggested that "changing the pressure in textbooks is achieved by changing the gravity of objects." I think it is easy for us to confuse pressure and gravity here. " I think in this experiment, we only need to apply pressure on the surface of the wood block, and then observe whether the sponge sinks deeper when the pressure increases, and we can draw a conclusion. "Students' creative spirit is fully reflected. Then I ask my classmates, in addition to the experiment just now, can you design some small experiments through the equipment around you to explore this problem? Many students thought of this method: press the sharpened end of the pencil on your finger, and your hand will feel pain; Then increase the pressure, the pain will be strengthened, and the fingers will sink deeper, which shows that the greater the pressure, the more obvious the effect of the pressure. Then I took the opportunity to ask students how to explore "when the pressure is constant, the smaller the stress area, the more obvious the effect of pressure"? Students can generally think of a way: press the two ends of the pencil with the index fingers of both hands respectively. At this time, because the pressure of two hands on the pencil is equal (the two forces are balanced) and the stress areas of two fingers are different, the experimental results can be obtained through the different feelings of two fingers. So when you meet "if you buy rice in the supermarket, what methods will you think of to reduce the pressure on your opponent in the convenient bag?" Students will be able to solve these problems. First, divide the rice into two bags to reduce the pressure. The second is to put a cloth between the bag and the hand to increase the stress area. In addition to doing experiments in class, I also supplement some extracurricular activities, such as investigation, experimental exploration, small production and so on. For example: investigate and study cases related to pressure increase and decrease in life, and investigate and study the relationship between atmospheric pressure change and weather; Experimentally explore and measure your own pressure on the ground; Homemade water barometer and so on. Through these expansions, students' interest in exploring new knowledge is stimulated, their thinking ability is cultivated, and the importance of learning physics knowledge is reflected.