Physical principle
First, study textbooks.
The purpose of learning textbooks is to find out what are the "four points" (key points, difficulties, key points and value points) in textbooks.
For example, the "four points" of "friction": key points: sliding friction (production conditions, size calculation, direction determination). Difficulties: the condition of friction, the determination of direction and the determination of static friction. Key points: analyze the force of the object and determine the relative motion/trend. Value point: deepen the understanding of "relativity of movement/trend"; Deepen the understanding of the thought of "concrete analysis of specific problems"; Understand the specific methods of using and controlling friction in actual production and life.
Second, pay attention to the connection between knowledge points.
There should be more intersections, connect knowledge points with each other, and weave the learned knowledge into a net. It is a very good method to use the correlation between knowledge points to connect these related test sites (and understand the differences) and lay a solid foundation. For example, if we study the chapter of celestial motion satellites, we should deeply understand this part, and we can look at the related concepts of Bohr energy level model.
Third, training physics problem-solving methods
Relatively speaking, there are traces to follow in solving physical problems. Sketch-think about the scene-choose the object-analyze the topic, limit the conditions, make clear what you want-list the equations-check. You can train each question in this way, and of course you can omit some steps for different questions.
Fourth, pay attention to the physical notebook and the wrong book.
notebook
1. Remember the definition. Some basic formulas in textbooks have corresponding explanations, such as the formula of universal gravitation between two objects: F∝Mm is directly proportional to the mass of two objects, and r is inversely proportional to the square of the distance between two objects, that is, F∝ 1/r? The constant of gravity is g. . . Get: f = mmg/r？ .
2. Record important concepts, laws and principles in your own language. Such as Lenz's law, deflection field.
3. Record the comprehensive examples explained by the teacher in class, and make detailed notes to try to figure out. These questions comprehensively apply and examine many knowledge points, which can play a role in covering one question.
error logging
1. Record some methods and skills. For example, after learning the momentum theorem and kinetic energy theorem, the momentum theorem (ft=p/-p) is used when the topic touches the time division, and the kinetic energy theorem (fs=ek/-ek) is used when the displacement is touched.
2. Record valuable typical topics. Choose different angles to think, and extract some thinking methods from them.
3. Record and summarize some concise and practical inferences or conclusions. For example, "the potential decreases along the electric field line"; "The tension on the same rope is equal"; "Maximum speed at zero acceleration"; "Lorentz force does not do work" and so on.
4. Record the knowledge structure. From the whole knowledge structure of physics to the knowledge structure of mechanics and electricity, even to chapters, such as the knowledge structure of electric field.
Fifth, pay attention to physical models and physical processes.
Be sure to find out which model or combination of models the topic is, so as to help students classify the topic and roughly determine what knowledge to use to solve the problem. After completing a problem, if you can be familiar with the physical model behind the problem, you can accumulate experience for solving problems in the future.
In the process of examining questions, we should develop the habit of drawing schematic diagrams. In order to solve physical problems, we can draw pictures as much as possible. Pictures can help us understand the meaning of the problem, the analysis process and the changes of various physical quantities during the discussion.
chemistry
A thorough understanding of the periodic table of elements
The periodic table of elements is the most important place to study chemistry. The most important experiments and theories that embody the periodic table of elements must be understood. Learning the periodic table well can explain many problems.
For example, experiments on the reaction rates of sodium, potassium and magnesium with water respectively. The third cycle reflects the strength order of oxygenated acids with nonmetallic properties.
For example, why can HF corrode glass SiO2 _ 2, but HCl, HBr and HI can't?
Because F is more nonmetallic than O, Si-F bond has greater bond energy, shorter bond length and more stable bond than Si-O bond. Therefore, the reaction direction of SiF4 formation is more stable than that of SiO2. O is more nonmetallic than Cl, Br and I, so hydrochloric acid, hydrobromic acid and hydroiodic acid cannot react with SiO2.
Second, master the basic concepts of chemistry, summarize the types of questions and solutions.
Master basic concepts, such as element symbols, chemical formulas, chemical equations, properties of elements and compounds. When doing problems, you should be good at summarizing the types of questions and solving ideas. Chemistry has strong laws. If you master these laws, you can control knowledge freely. For example, the general law of valence: metal elements usually show positive valence, nonmetal elements usually show negative valence, simple elements have zero valence, many elements have valence changes, different conditions have different valence States, and so on.
Third, visualize and concretize abstract knowledge.
Some very abstract knowledge, such as extranuclear electron configuration, law of motion, ionization of electrolyte, chemical bond and spatial configuration of molecules, etc. We might as well model it visually first, and then discuss its essence in depth. Only by understanding can we have a deeper memory. In learning, visualizing some concepts and theories scientifically is helpful to deepen understanding and improve memory effect.
Fourth, enhance hand-drawing ability.
We need to master electronic and structural (simplified) formulas, and use them to analyze various reactions in an attempt to find laws. This is a very important ability, especially for organic chemistry. We need to master electronic and structural (simplified) formulas, and use them to analyze various reactions in an attempt to find laws. This is also the basic skill of organic reasoning. Now you don't need to master the mechanism, just find the law.
For example, the chlorination reaction of methane: h3c-H+Cl-cl = light = h3c-Cl+H-cl, we can catch "H+Cl" with one hand, and then turn 180, hey, it becomes "Cl+H". We call this "rule of the game" "substitution reaction".
Fifth, pay attention to the idea of reciprocity.
The idea of equivalence is very important in all disciplines, and it is the key step to find isomers. Of course, the first few steps are to calculate the degree of unsaturation, select the matrix and find out the heteroatoms or groups. Then it's not random.
At this time, heteroatoms are divided into several categories: monovalent groups (-Cl, -R, -OH, etc. ), bivalent bases (-O-, -CH2-,-COO-,etc. ) and polyvalent bases (nitrogen atoms). Dealing with monovalent groups and finding equivalent hydrogen on the matrix, there are several ways to replace equivalent hydrogen, so there are several isomers. To deal with divalent groups, we just need to find equivalent bonds on the matrix, and there are several isomers in several insertion methods. Note that divalent groups such as ester bonds have forward insertion and reverse insertion. The specific method of treating multivalent groups is explained in the examples. In fact, multivalent groups are specially used to deal with nitrogen atoms linked to three substituents.
Sixth, find an analogy.
Chemistry is by no means a subject of rote learning (except the first multiple-choice question), but a subject with rules to follow. For example, the magic of "pseudo-halogen" is that its chemical properties are very similar to halogen, such as (CN)2, H2O2, NO2(N2O4) and so on. For example, they are generally very oxidizing and can be disproportionated in water; Therefore, we can infer the reaction of (CN)2+H2O←=→HCN+HOCN.
Typical is the periodic law of elements, which is worth summarizing, such as the acidity and redox of oxyacids. For example, the reaction between NaOH and Al can also be extended to boron, 2 NaOH+2 b+2 H2O = △ = 3 H2 = 2 "nabo2", which is called "sodium metaborate". Like sodium metaaluminate, it basically exists in the form of [M(OH)4].
There are also three pairs of diagonal rules Li~Mg, Be~Al and B~Si. Therefore, it can Be inferred that Li will not generate peroxide when burning in air, and Be and Si can also react with NaOH solution to generate hydrogen. In addition, we can also compare the similarities and differences between the order of oxidation and electronegativity.