1In chemistry teaching how to make students learn knowledge of elements and compoundsElements and compounds, the nature of knowledge means that the substance, structure, purpose, the presence of form in nature, preparation methods. The present junior high school chemistry textbook on the air, oxygen, water, hydrogen, carbon and compounds, iron, acid, alkali, salt, oxides of knowledge, all belong to this part of the content. This part is characterized by knowledge of many points, covers a wide range, with the production and living close to, practical, strong; easily understood and difficult to remember. In response to these characteristics, the study should be aware of the following four questions: First, grasp the nature, strike a balance between Only by grasping the nature of the material, we can 2rationalize the structure, properties, uses, the existence of the relationship between the system of law, and can be linked to organic knowledge. 1, structure a one-use nature of The relationship between the nature and uses easy to distinguish, that is the nature of use, reflecting the nature of use. Such as the density of hydrogen is small, can be used to fill balloons; with flammability, combustion heat release, can be used as fuel; with a reduced condition, can be used for smelting metal; be able to respond with a variety of materials is an important chemical raw material, can be used in the synthetic ammonia, hydrochloric acid system. The relationship between the nature and structure: the 3structural characteristics of the material determines the nature of the material, the nature of a reflection of structural characteristics. If pure hydrogen combustion in oxygen in the quiet; while hydrogen and oxygen gas mixture ignited, often they will explode. Why? To find out this problem, we should from the hydrogen molecules and oxygen molecules begin to consider the exposure. Pure hydrogen is burned, only in the “surface” and the oxygen contact, “internal” and oxygen molecules intrusion; while the oxygen and hydrogen gas mixture, the two kinds of molecules evenly mixed together, full access. Therefore, the same reaction of hydrogen and oxygen, the intensity of the big difference. Knowledge of physical structure, including a number of areas, in studying the chemical properties of a single quality, the main contact characteristics of atomic structure. Such as the hydrogen molecules are hydrogen atoms, hydrogen nuclei is only an outer electron, it can use this electronic and with other elements such as oxygen 4atom (atom, chlorine atom) combination, so easy to hydrogen and oxygen, chlorine and other reactions, that is, the performance of out of flammability, reduced. Chemical properties of compounds in the study, the main characteristics of the molecular structure of contact, namely, the given compounds are ionic compounds or covalent compounds, each element shown in valence such a system. Such as different acids in the chemical nature of the reason why there are similarities, it is because they are ionized in aqueous solution, where the cations are all out of hydrogen ion; different alkali reason why there are similarities in the chemical nature, because they are in aqueous solution, where ionization of the anion out of all hydroxide ions. 2, there is the nature of a method for making a Nature of the material will have a direct impact on its existing form in nature. If the nature of noble gas 5stability, and generally do not respond with other substances, so in the natural world form a single quality; while aluminum, zinc, iron and chemical properties of the more lively, so they are in the earths crust in the form of compounds exist. On the contrary, if an element in nature mainly in compound form, that shows that the chemical properties of this element more lively, and this is the nature of the material and the presence of the relationship between. Material properties and the presence of form in nature, but also determines the substance of the preparation method. If the air contains a single qualitative form of oxygen element on the direct use of industrial air-liquid separation method to obtain the system of oxygen, as potassium chlorate, potassium permanganate and other compounds containing oxygen -2 price element, the laboratory can be used heat way to decompose potassium chlorate, potassium permanganate, so that the element oxygen valence rise in the price from -2 to zero price, so 6that oxygen was released from the elements, to be oxygen, which is the existence of material forms and preparation methods between the relationship. Second, practice, apply their knowledge Knowledge of specific elements and compounds, typical of the material and more practical, with the daily life and agricultural and industrial production closely related to learning when to use what they have learned to be consolidated and deepened. If the walls of stone mortar Ma Guo, began to feel wet, over a period of time