What are the chemistry questions in junior high school and how to answer them?
1, multiple-choice answering skills, accurate marking, regardless of speed, no extra points for quick answering. Remember not to be impetuous when answering questions, and read the questions clearly before writing.
2, fill in the blanks/short answer questions, memory-based questions, only need to recall what you have learned when answering.
3. Infer the answering skills, mark them well, mark the problems in the stem of the questions and turn them into useful information.
4. Experiment to explore the answering skills. Keeping a steady mind and exploring questions are the most difficult questions in the senior high school entrance examination, but not every empty place is difficult.
5, calculation questions answering skills. Carefully examine the questions, read the stem of the questions, analyze the meaning of the questions, and find out the core response equation.
Answers to junior high school chemistry questions
1, multiple choice questions
Look carefully at the questions and options before you start to answer them, so as to reduce the probability of making mistakes because you can't see the meaning and answer of the questions carelessly. Mark questions appropriately, and mark negative statements, for example, questions require incorrect or wrong choices, so as to remind yourself not to choose the opposite answer. In the exam that requires an answer sheet, we must pay attention to checking whether the answer sheet is consistent with the answer obtained.
2. Fill in the blanks/answer short questions
The topic of reciting basic knowledge is relatively simple. Pay attention to what the topic asks. For chart-based questions, we should summarize the relevant laws in the chart through the horizontal and vertical comparison of data and the judgment of special values, and then start answering questions. Open-ended questions, under normal circumstances, will give corresponding reactions or statements to things that appear in the stem of the questions. I have read the meaning of the question clearly and answered it with the relevant knowledge points in the book.
3. Inference problem
Mark some key information in the topic, such as the chemical formula or common name of a substance, connect it with the corresponding knowledge points, and then infer the substance that will produce this phenomenon by combining a phenomenon in the topic. After inferring the essence, check it again to see if you can restore the reaction or phenomenon in the topic, and then think about whether there are other possibilities.
4. Experiment to explore the problem
Chemistry is an experimental subject, and experimental inquiry questions also occupy a large proportion in the chemistry examination, which is also a difficult point in the senior high school entrance examination, but it is not difficult everywhere. When doing experimental inquiry questions, we should first find the purpose of the experiment from the questions and don't deviate from it, and then make a judgment according to a conclusion, phenomenon and knowledge learned in the textbook. Some topics also require you to design an experiment to judge or prove a current or conclusion. When designing experiments, we should pay attention to control variables and set up control groups.
5. Calculation problems
It is not difficult to calculate the problems in chemistry for the senior high school entrance examination. When doing the problem, you should carefully examine the problem, find the reaction equation according to the meaning of the problem, and find the data to solve the problem according to the stem analysis. Usually we use the law of conservation of mass to calculate, and the answering steps should be complete.
Expanding reading: a summary of junior high school chemistry learning methods. There are three points to learn chemical knowledge, namely, grasping the basics, grasping the ideas and grasping the rules.
We should attach importance to the study of basic knowledge, which is the guarantee to improve our ability. Learn chemical terms, such as element symbols, chemical formulas, chemical equations and basic concepts, and the properties of elements and compounds. Doing problems should be good at summarizing classified problems and solving problems. There are inherent laws between chemical knowledge. If you master the rules, you can control and remember knowledge. Such as the general law of valence, metal elements usually show positive valence, nonmetal elements usually show negative valence, the valence of simple elements is zero, and many elements have valence changes, and the valence States are different under different conditions. For another example, the gas generating device needed to make oxygen in the laboratory is a test tube. The rule is that as long as the solid is heated, no matter whether one drug or two drugs are used to make gas, the same device as oxygen is used-that is, the test tube. Grasping the law can be used, for example, to tell the laboratory that methane gas is heated by mixing sodium acetate and alkali lime. Although we have not learned this part of knowledge, we know that it is the same as the oxygen sample according to the law of the device for heating solid to prepare gas. For example, according to the calculation of chemical formula, we should pay special attention to ideas. What problem is calculated by chemical formula, that is, as long as there is the mass fraction of elements, it must be calculated by chemical formula first.
Learning method of compound knowledge of elements
First, the characteristics of knowledge of elemental compounds
1. Elements and compounds are closely related to basic concepts and theories, and should be combined well. For example, the physical properties of diamond and graphite, which are composed of carbon elements, are very different, and the properties of sulfuric acid are essentially different because of the different concentrations and dilutions. Therefore, we must link the essence of matter with basic concepts and theories.
2. The knowledge of elements and compounds is closely related and has strong regularity. The knowledge system is from simple materials to compounds in the order of existence, nature and use. The existence, preparation and use of substances depend on their properties. Therefore, when learning to drive the rest, we should firmly grasp the essence of matter. If we infer the use and existence of hydrogen according to its flammability and reducibility, we should not learn by rote.
3. Elements and compounds are rich in knowledge, that is, they have the characteristics of individuality and individuality. Therefore, we must comprehensively analyze the problems in learning, that is, the characteristics of memorization and memorization. For example, HNO3 _ 3 has the generality of acid, and has the characteristic of reacting with metal to generate water instead of hydrogen.
4. The knowledge of elements and compounds is highly dependent on experiments, and most chemical knowledge is obtained through experiments. For example, the chemical properties of oxygen, through the demonstration experiments of C, P, S, Mg and candles, let you realize that oxygen is a more chemically active gas. Therefore, we must carefully observe and analyze the experimental phenomena, so as to be impressed, remember firmly and understand thoroughly.
Second, how to learn?
1. Pay attention to the guiding role of theory. For example, the preliminary knowledge of material structure reveals the properties of elements, especially the relationship between the chemical properties of elements and the outermost electron number of atoms, reveals the nature of chemical reactions, and reveals the nature of molecular formation and valence. This laid a theoretical foundation for correctly writing chemical formulas and chemical equations.
2. Summarize the laws and master the characteristics of matter. It is necessary to grasp typical substances, sum up general laws, grasp the characteristics of substances, and improve the ability to analyze and solve problems. For example, by studying organic compounds, it can be concluded that methane, methanol, ethanol and acetylene candles all react with oxygen to produce carbon dioxide and water, but they all have different physical properties. Another example is the study of acid in Chapter 8, which summarizes the general laws of acid through the chemical properties of hydrochloric acid, sulfuric acid, nitric acid and phosphoric acid, but the characteristics of different acids should also be clear. For example, the water absorption and dehydration of concentrated H2SO4 and the strong oxidation of nitric acid should be fully grasped, otherwise mistakes will be made.
3. Regularly sort out and summarize the knowledge learned, pay attention to vertical and horizontal links, and form a knowledge network. Although the knowledge of elemental compounds is numerous and fragmentary, according to their relationship, they can be linked into a knowledge network centered on a certain substance, making scattered knowledge systematic, structured and organized.