Three rounds of review. The first round of review is the review of units and chapters of basic knowledge. Through the first round of review, students can systematically master basic knowledge, basic skills and methods, and form a clear knowledge network and a stable knowledge framework. We start with the double basics, closely follow the knowledge points of the senior high school entrance examination and organize the units to pass the customs. Combined with the actual situation of students, strict unit clearance is carried out, and the basic knowledge is consolidated for some C and B students through diligent investigation, multiple questions and multiple repetitions. On the basis of mastering knowledge flexibly, we also pay attention to cultivating students' reading comprehension, problem analysis and problem solving ability.
The second round of review breaks the boundaries of chapters and implements large unit, small comprehensive and special review. The second round of review is by no means the compression of the first round of review, but the process of synthesizing, consolidating, perfecting and improving the knowledge points. The main task and goal of review is to complete the sorting, induction and integration of all parts of knowledge, make all parts of knowledge an organic whole, and strive to realize the focus of basic knowledge, the networking of key knowledge, the questioning of network knowledge and the life-oriented problem design. This round of review should take mathematical thinking methods as the main line and students' comprehensive training as the main body, reduce repetition and highlight key points. In the application of mathematics, we should pay attention to the integration of mathematics knowledge with life and other disciplines, interspersed with special review (such as chart information questions, economic decision-making questions, open questions, project design questions, exploratory questions, etc. ), thus infiltrating students' awareness of life-oriented problems, thus improving their understanding ability of reading comprehension questions.
The third round of review is the stage of deepening and consolidating knowledge and ability. Review the organization of materials in order to give priority to the test questions and simulation questions in the senior high school entrance examination, give kickbacks to the teaching materials, make up for missing items and strengthen training. At the same time, we should teach students some necessary skills and methods to take the exam, so that students have enough confidence to face the senior high school entrance examination calmly. Due to the nervous study before the exam, some students are easy to be anxious and impetuous, which leads to the decline of learning efficiency. At this stage, we should also pay attention to adjusting students' mentality in time so that they can take the senior high school entrance examination with the best mentality.
The Golden Plan of Mathematics Review for Senior High School Entrance Examination
Lay a good foundation and improve your ability. Review time is tight and the task is heavy. In a short time,
How to improve the efficiency and quality of review is a concern of every junior three student. To this end, let me talk about.
Some of my own ideas are for your reference.
First, lay a solid foundation.
1. Pay attention to textbooks and review them systematically. Junior high school mathematics foundation includes basic knowledge and basic skills.
Two aspects. At present, the proposition of the senior high school entrance examination is still based on basic knowledge questions, and some basic questions are in the textbook.
The original title or transformation, although the big topic behind it is "higher than the textbook", the prototype is generally a textbook.
The exercises in the textbook are the extension, deformation or combination of the topics in the textbook, which should be reviewed in class.
This is the main thing.
For example, in 2004, the senior high school entrance examination in Liaoning Province 17: AB is the chord of the circle O, and P is on the chord AB of the circle O.
A little, AB 10cm, AP 4cm, OP 5cm, then the radius of the circle o is ().
Centimeter.
This question is the original title of the third grade geometry textbook. There are still many such problems that tell us to study hard.
The importance of textbooks. When reviewing, you must dig deep into the textbook and summarize the contents in the book.
Make it form its own knowledge structure, especially after class, reading and thinking, and some problems in middle school.
On this basis, extend and expand. Blindly engage in sea tactics and exercise a lot all day.
The effect of the problem is not good, so we should pay attention to the induction and arrangement of the problem-solving methods when doing the problem.
Infer from others.
2. Lay a good foundation and learn to think. Nearly 70 of the senior high school entrance examination is divided into basic questions. If you put the middle question and
Compared with the basic points in the problem, the proportion will be greater. Therefore, when applying the basic knowledge, we should
Be skilled, correct and fast. You should not only listen to the teacher in class, but also dare to question and think positively.
Testing methods and strategies should be "experienced" and "learned" by teachers.
Especially in the process of solving the new situation and problems, we should realize how to think correctly.
3. Pay attention to the understanding of basic knowledge and the study of methods. Basic knowledge is not only related to junior high school.
Concepts, formulas, axioms, theorems, etc. To master the connection between basic knowledge, be rational.
Clear the knowledge structure, form the whole knowledge, and can be used comprehensively. For example, the dynamic scores involved in the senior high school entrance examination
Problems are not only the combination of equations, inequalities and function problems, but also often involve geometry.
Similar triangles, proportional deduction and so on.
In addition to the basic knowledge, the mathematical proposition of the senior high school entrance examination also attaches great importance to the examination of mathematical methods.
Check. Such as collocation method, substitution method and discriminant method.
Second, comprehensively use knowledge to improve their own ability.
The basic abilities of junior middle school mathematics include calculation ability, thinking ability, spatial imagination ability and body.
The ability to link modern mathematics with production and life-related disciplines and so on.
1, improve the ability to solve problems by using mathematical knowledge comprehensively. Ask students to be able to put
The knowledge in each chapter is related and can be used comprehensively to avoid analogy. Immediate instruction
Paragraphs should be reviewed according to their own reality, and the knowledge should be summarized and answered.
Methods induction.
Throughout the examination of the ability in the senior high school entrance examination, it can be roughly divided into two stages: one is the examination operation.
Ability, spatial imagination, logical thinking and the ability to solve pure mathematical problems; The second one is
Emphasize reading ability, innovative exploration ability and mathematical application ability. When doing problems at ordinary times, you should do the following:
1) Only by deeply understanding the nature of knowledge and strengthening the exercise of one's ability to examine questions at ordinary times can we make changes.
The expression of the proposition is unhurried and handy. 2) Seek different ways and changes to solve the problem.
Pass on the way of thinking. Pay attention to the broadness of your thinking and find different ways for the same topic.
Methods, to achieve multiple solutions to one problem, thus helping to break the mindset, open up ideas and optimize solutions.
Questioning method. 3) After changing the position, shape and size of geometric figures, we can find the relationship between them.
Department, know which quantity hasn't changed and which quantity has changed. For example: front and back folding in the folding problem.
Conformity is the key to solving problems.
2. Pay close attention to key contents and practice hot issues appropriately. Over the years, the "square" of junior high school mathematics
"Process", "function" and "line type" have always been the key contents of the senior high school entrance examination. Equation thinking,
"Function Thought" runs through the examination paper. In addition, "open questions", "exploratory questions",
Problems such as "reading comprehension questions", "scheme design" and "hands-on operation" are also in recent years.
Most of the hot questions in the exam come from textbooks, and some don't require profound knowledge.
The same, but the topic is novel, the background is complex, and the text is long and difficult to sort out. Pay attention to this aspect.
In the face of study and training, in order to be familiar with and adapt to this kind of questions. How to Review Mathematics for Senior High School Entrance Examination
First of all, as candidates, we must understand the relevant policies of the senior high school entrance examination and avoid detours and going the wrong way. Candidates should carefully study the Instructions for the Senior High School Entrance Examination, understand and see clearly the scope of the examination, focus on the grading standards in the reference answers of sample questions, remember every grading point, and avoid "skipping" when solving problems.
Second, know yourself and build self-confidence. After all, the senior high school entrance examination is not a college entrance examination. Its main function is to understand the mathematics learning process of students in compulsory education and evaluate their basic level of mathematics. Secondly, it is the main basis for high school enrollment. Looking at the senior high school entrance examination questions all over the country in recent years, the difficulty distribution of the test papers is mostly controlled at 4: 5: 1 or 5: 4: 1. Therefore, candidates don't have to doubt their math ability and level because they can't solve some math problems. It can even be said that as long as they work hard in the review stage of this semester, they will not make mistakes in the senior high school entrance examination.
Third, make a review plan and arrange the review time reasonably. Generally speaking, three rounds of review can be arranged for the senior high school entrance examination review. The first round, find out the context of junior high school mathematics content and review the basic knowledge system. According to the knowledge system of junior high school mathematics, the content of Chapter 21 can be summarized into eight units: ① number and formula {real number, algebraic formula, fraction, quadratic root} ② equation (group) and inequality (group) {linear equation (group), linear inequality (group) and quadratic equation. About 60% of the questions in the senior high school entrance examination belong to the "double base" that students usually study. In order to ensure the score of this sub-topic, we must systematically review the teaching materials and make clear what we must master. Here, I suggest that all candidates must first cooperate with your teacher to review, don't take a cursory look, aim too high, and don't make another set; Secondly, review should be accompanied by appropriate exercises, and the difficulty of exercises should be controlled, mainly in middle and low grades. In addition, we should develop the good habit of marking questions that we find difficult or easy to make mistakes, so that we can review them in the second stage. Note: it is not easy to train the questions too early, and the reference materials should be in units. At this stage, the review should be detailed, not cursory.
In the second round, focus on the hot spots, grasp the weaknesses, and review the difficult knowledge specially. The purpose of learning mathematics is to use mathematics. In recent years, a large number of active, interesting and enlightening questions have emerged in the senior high school entrance examinations in various places. Candidates should carefully review these hot issues and make special breakthroughs under the guidance of teachers. Hot topics generally include: reading comprehension, open inquiry, practical application, geometric algebra synthesis, research-based learning and so on. Note: You should have a compilation of the senior high school entrance examination questions in various provinces and cities. We should know that the wonderful questions appearing in foreign examination questions are often the reference of local propositions.
In the third round, lock the target, prepare for the senior high school entrance examination and conduct simulation training. After the first and second rounds of review, the basic knowledge of learning has basically passed, and the third round of simulation training should be in the middle and late May. Its purpose is to check and fill the gaps, adjust the examination psychology, and enter the examination room in the best state. Candidates are advised to use test papers from all over the country, set standard time and conduct self-simulation tests in addition to normal simulation training in schools. Note: Self-grading should be based on grading standards, and you can't just look at the answers without looking at the scores.
The general review of junior high school mathematics has gone through three rounds. In the first round of review, the following questions often appear:
1. Review is unplanned and inefficient, which is reflected in inaccurate key points, inappropriate details, low difficulty, and inaccurate grasp of the upper and lower limits of the outline and teaching materials.
2. The review is not solid, and there are many loopholes, which are reflected in the high score of 1), which is too difficult and loses a lot of basic knowledge. 2) The review speed is too fast, and there are countless problems in students' minds. It's too late to rework. There are many loopholes if you don't rework. 3) the requirements are too loose, the requirements for students are not implemented, and a large number of review materials are only sorted out and not corrected; No homework.
3. There are many questions, and the ability is not high, which is manifested in: 1) taking the title as the topic instead of the title method, being satisfied with the answers after solving the problem and ignoring the summary of the law of solving the problem. 2) The topics are out of order, not step by step. 3) Too many repetitive topics, resulting in a waste of time and energy.
In the second round of review, the following problems should be prevented:
1. Prevent the mechanical repetition of the first round of review.
2. To prevent simple questions, we should use the topic theory method.
3. Prevent too many problems
In the third round of review, the following problems should be prevented:
1. Do more exercises, practice instead of speaking.
2. Use review materials instead of coaches, do not prepare lessons, and the classroom organization is loose.
3. Only pay attention to knowledge counseling, not psychological training.
Suggestion:
Let the students learn from their mistakes, make some comments and set up their own error files. For valuable questions, ask students to sum up what knowledge points are examined in the question, from which angle each knowledge point is examined, what mathematical thinking methods are examined in the question, what are the solutions to this problem, and what is the best solution? When I make a mistake, is it a mistake in knowledge or method, a mistake in solving problems or a mistake caused by psychological defects? Effectively solve the problems of seeing but not right, being right but not complete, being whole but not beautiful.
1. You must listen carefully in physics class, or spending twice as much effort after class will not have such a good effect.
2. Do more exercise. If you don't understand, be sure to ask at once. If you can't ask, write down the pages in your notebook. There are many problems to contact, and the exam is just a piece of cake.
3. Read the wrong questions when you don't have time to review, and you must understand what you don't understand.
If the teacher in this class is not very good at explaining the topic, ask the better teacher in the next class while the teacher is away.
Be sure to keep a calm mind and master the time during the exam.
Review guidance of chemistry in grade three.
The most basic feature of nine-year compulsory education is quality education, and the syllabus and teaching materials of nine-year compulsory education are not only the basis for implementing quality education, but also the basis for examination.
With the continuous reform of senior high school entrance examination system, in order to better reflect the purpose of chemistry teaching, highlight the guiding role of quality education, pay attention to students' learning ability, reduce students' excessive academic burden, and cultivate students' innovative consciousness and practical ability are the fundamental starting points of senior high school entrance examination reform.
1. Analysis of chemical trend of senior high school entrance examination in recent years
Through the analysis of the propositions of the senior high school entrance examination in recent years, it is found that there are four more and three less: that is, the key contents stipulated in the syllabus are linked with the social reality and the reality of students' life, and the number of propositions is increased; Subjective and open propositions that help to test students' innovative consciousness and practical ability increase; The number of propositions related to experimental investigation has increased; The proposition of interdisciplinary knowledge connection to solve chemical comprehensive problems has increased. However, the recitation proposition of chemical knowledge is greatly reduced; Partial problems, strange problems and complex solubility calculation problems are also greatly reduced; The total number of difficult problems and test questions has decreased.
Therefore, when reviewing, we should pay attention to the following points:
(1) Highlight the comprehensiveness and foundation of quality education: Focusing on the overall goal of quality education stipulated in the basic requirements, the review content should not only cover key concepts and principles, important substances, important chemical terms, basic experiments and calculation skills, but also penetrate the scientific attitudes, viewpoints, emotions, methods and abilities required by the basic requirements, and encourage students to cultivate basic qualities.
(2) Pay attention to chemistry education and the times: pay more attention to and read extracurricular newspapers and books, watch more news broadcasts, listen to more news broadcasts, understand new scientific and technological achievements and new developments, social hotspots and countermeasures, and broaden their knowledge and application fields. In order to enhance their psychological control ability and acquire strategic knowledge.
(3) In learning and reviewing methods, we should pay attention to the interrelation between knowledge points, constantly expand the connotation and extension of knowledge, and focus our study on building a network system of knowledge and improving the ability to use knowledge, so as to quickly retrieve and transfer the knowledge we have mastered when solving problems.
Two. Examples of key points, difficulties and hot spots
1. Key points of the exam
(1) Judgment of physical change and chemical change
(2) Purity, mixture, simple substance, compound and their identification.
(3) Writing chemical formulas and chemical equations and distinguishing right from wrong.
(4) Inference of valence and structure of atoms
(5) The writing and meaning of small numbers around element symbols, and the meaning of chemical formula.
(6) fluidity of metal and acidity and alkalinity of solution
(7) The concept and identification of acid, alkali, salt and oxide.
(8) Four basic reaction types, oxidation reaction and reduction reaction, oxidant and reductant.
(9) Properties of oxygen, H2, carbon, carbon monoxide, carbon dioxide and H2O (oxidizability, reducibility, flammability, stability, etc.). ) and their comparison and identification.
(10) Preparation, collection, detection and purification of three common gases (H2, O2 and CO2)
(1 1) comprehensive experiments such as material preparation, impurity removal, drying, conversion inspection and tail gas treatment.
(12) Properties, Impurity Removal, Transformation and Identification of Common Acids, Alkalis and Salts
(13) Calculation of chemical formula, chemical equation, solubility and mass percentage concentration
2. Difficulties in exams
(1) Content from the test center:
(1) to judge the possible reactions between various substances;
② Identification, purification and impurity removal of substances (ions);
(3) Explain or explain the problem with laws or principles;
④ Comprehensive experiment.
⑤ Comprehensive calculation of mass percentage concentration, solubility and chemical equation.
This kind of difficulty is difficult to compare, analogy, explain or calculate on the basis of the essential differences and internal relations of various kinds of knowledge, and it is also difficult to lack clear ideas and methods for solving problems.
(2) From the perspective of questions, there are discussion questions, reasoning questions, experimental design questions, open questions, exploratory comprehensive questions, comprehensive calculation questions, and answers to some questions that integrate theory with practice.
Step 3 investigate hot spots
(1) environment and chemistry
Example 1. Shanghai is listed as one of the 36 cities short of water in China, and predicted by the United Nations as one of the six cities with serious shortage of clean drinking water in the world in 2 1 century. The main reason for water shortage is ()
The water pollution in the upper reaches of this river is very serious. B. Shortage of fresh water resources
C, uneven rainfall D, the water intake point is far away from the urban area.
Example 2. Formaldehyde (chemical formula is CH2O) is the main component of indoor air pollution, which comes from paint, plywood, chemical fiber carpet and other materials used in indoor decoration. The following statement about formaldehyde is true ()
A. The formaldehyde molecule consists of a carbon atom and a water molecule.
B The mass ratio of C, H and O in formaldehyde is 1: 2: 1.
C. The atomic number ratio of C, H and O in formaldehyde molecule is 1: 2: 1.
D. formaldehyde is an oxide.
Example 3. The theme of World No Tobacco Day on May 3 1 last year was: Clean the air and reject "second-hand smoke". "Secondhand smoke" contains a toxic gas, which can combine with hemoglobin in human blood. This gas is ()
A.C.CO N2 CO2
Example 4. The following measures or operations will not cause pollution or damage to the environment ()
A. Excessive felling of forest trees
B. A chemical plant uses a lot of sulfur-containing coal as fuel.
C. Using wind energy and solar energy to generate electricity
The tail gas of CuO reduction in D.CO is directly discharged into the atmosphere without treatment.
Comments: The above examples show that chemical knowledge is closely related to the environmental problems we are facing. From the fact of global or regional environmental pollution, or the fact of environmental pollution in factories and families, we use relevant knowledge, abilities and viewpoints to examine the causes, basis and process of environmental pollution, and put forward our own views and suggestions. So as to guide and cultivate students' feelings of caring about society and nature, establish confidence in transforming the environment with what they have learned, and understand the charm and value of chemistry.
(2) Energy and chemistry
By 2005, "West-to-East Gas Transmission" will bring 3 billion square meters of natural gas to Shanghai. The main component of natural gas is methane (CH4), which is a kind of "clean energy". Methane burns completely in the air, producing carbon dioxide and water. Write the chemical equation of this reaction. City gas usually contains carbon monoxide gas. Write the chemical equation of carbon monoxide combustion.
. Compared with natural gas, from the safety point of view, the main disadvantages of natural gas are
. From the point of view of environmental protection, among gas, natural gas and hydrogen, the preferred fuel is.
Coal mines must take safety measures such as ventilation and prohibiting fireworks to prevent explosion accidents. The main gas causing the explosion is ()
A.CO methane N2 carbon dioxide
(1) It is reported that a batch of fake and shoddy goods seized in Fujian Province have been "green destroyed" recently. The so-called "green destruction" refers to changing the previous practice of burning fake and shoddy goods with gasoline and replacing it with the destruction methods of rolling, pulping and recycling. What do you think is the advantage of this?
.
(2) Recently, a report by Xinhua News Agency revealed that a huge "combustible ice" belt was found at the bottom of the South China Sea, and the total energy was estimated to be equivalent to half of China's total oil; The reserves of "combustible ice" in the East China Sea are also considerable ... The main component of "combustible ice" is methane monohydrate crystal (CH4? H2O). Please answer the following questions in combination with junior high school chemistry knowledge:
(1) The following statement is correct.
A.CH4？ Water in H2O crystal is a solvent.
B.CH4？ H2O has three components.
C.CH4？ The mass ratio of H2O methane to H2O is 1: 1.
D combustible ice can burn, indicating that water is combustible.
The discovery of combustible ice has opened up a broad prospect for China to use efficient new energy in the new century. There are (at least two) new energy sources that you think can be developed and utilized.
Comment: The energy crisis is a problem that the whole world must face. From the national policies and major measures of energy utilization in China to the safety of energy utilization, we can use our chemical knowledge for education and ability test. So as to guide students to care about and save energy from the height of human survival and development, and to understand the coping methods and even escape smoothly when there is a major safety accident in energy utilization. Combine chemistry with cherishing life.
(3) Life and Chemistry
Example 1. In China, qualified iodized salt is widely used, that is, a small amount of potassium iodate (KIO3) is added to salt. In potassium iodate, the valence of iodine is ()
A.+ 1 B.+3 C.+5 D.+7
Example 2. In food gift boxes, there is often a pack of quicklime as a desiccant, and the main component of quicklime is ().
A. calcium carbonate, calcium hydroxide, calcium oxide and calcium sulfate
Example 3. Excessive uric acid (C5H4N4O3) in human body can cause gout and kidney calculi, and purinol (C5H3N4OH) can be used for treatment. They are composed of different kinds of elements (fill in "same" or "different"), and each molecule contains different numbers of atoms.
Example 4. Ether is an anesthetic used by human beings for a long time. Its molecular structure is shown below.
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In which the middle and short lines indicate the connection between atoms (for example, the structure of water molecules can be expressed as H-O-H). Ether is composed of three elements with a relative molecular weight of.
Example 5. TNT is a high explosive, and the following chemical reactions will occur when it explodes:
TNT+21O 2 → 28CO2+10H2O+6N2, then the elements that make up TNT are respectively, and their atomic number ratio is.
Example 6. Soluble barium salts can poison people. If you take barium chloride by mistake, you can use magnesium sulfate to detoxify. The reason is (expressed by chemical equation).
Comments: Combine the concepts and principles of chemistry with our human life, production and scientific research, and set up information by creating problem scenarios. To understand nature, transform nature and society, and reflect their values. Let knowledge "live", be closer to life and production, and feel that "life is full of chemistry". So as to stimulate students' enthusiasm and initiative, from passive memory of accepting conclusions and manual solution of tedious skills to initiative, and from the process of solving practical problems, experience and form the awareness of application, and stimulate students' ability. In this way, students can get rid of the heavy memory burden and enjoy the value and fun of application, thus developing their academic ability.
(4) Materials and chemistry
Example 1. 1999 Ahmed, Nobel Prize winner in chemistry? Xavier initiated a new field of "femtosecond (10- 15 seconds) chemistry", which made it possible to observe the motion of atoms in molecules by using laser spectroscopy. What do you think this technology can't observe is ()
A. Decomposition of reactant molecules in chemical changes B. Movement of atoms in the reaction
C. Formation of product molecules in chemical changes D. Internal structure of nucleus
Example 2. Nano-materials are considered as the most promising new materials in 2 1 century. Carbon nanotubes are hollow tubes composed of carbon atoms with a diameter of several nanometers (1nm= 10-9m). The following statement is wrong ()
A. carbon nanotubes are a new type of organic compounds.
B. If the carbon nanotube material is completely burned, carbon dioxide is generated.
C. There are many carbon nanotube tubes with large surface area and strong adsorption capacity.
D. The chemical properties of carbon nanotubes are stable at room temperature.
Comments: The combination of chemical knowledge and advanced scientific and technological materials embodies the correlation between chemistry and science, society, production and life, helps students feel the truth and value of chemistry, and truly embodies that "society cannot live without chemistry" and "chemistry is around us".
(5) Synthesis and chemistry
① Exploratory comprehensive problem
The pH of soil has a great influence on the growth of crops. Please design an experiment to determine the pH value of a piece of soil. (Write down the lab supplies and steps)
Solution: experimental supplies: beaker, glass rod, PH test paper, distilled water.
Experimental steps: 1. Take a soil sample.
2. Put 2g soil sample into a beaker, add 10~ 15ml distilled water, stir with a glass rod and let stand;
3. After the solution is clarified, dip the supernatant on the PH test paper with a glass rod, and immediately compare the test paper with the colorimetric card to get the pH value of the unearthed sample.
Description: The best scheme should be a method with reasonable design, simple steps, simple operation and common reagents. To measure the PH value of soil, firstly, sample, dissolve, stand and measure with pH test paper.
Example 2. There are six solutions; Hydrochloric acid, copper nitrate, potassium chloride, sodium carbonate, magnesium sulfate and silver nitrate are mixed in pairs and put into three beakers, and the obtained three cups of mixed solution are clear and transparent (under the experimental conditions, all slightly soluble substances exist in the form of precipitation).
1. Determine the solute of three cups of mixed liquid as (write the chemical formula of solute):
and
and
and
What is the basis of your judgment?
.
2. Use the most economical and simple method to distinguish which two solutions are contained in each of the three beakers, and briefly describe the operation process.
Solution: 1, copper nitrate and silver nitrate, magnesium sulfate, KCl and sodium carbonate.
Two substances in the same beaker cannot react with each other.
2. Observe the color of the solution first, and the blue color is the mixed solution of Cu(NO3)2 and AgNO3; Then take a test tube, pour 2ml of the solution into any remaining beaker, and then drop a few drops of blue solution into the test tube. If blue precipitate appears, the poured solution is a mixed solution of KCl and Na2CO3; If only white precipitate appears, the poured solution is a mixed solution of HCl and MgSO4.
Note: This topic is mainly to clarify the conditions of metathesis reaction and the solubility of substances. AgNO _ 3 should be selected first and grouped with unreacted Cu (NO _ 3) _ 2, because AgNO _ 3 is mixed with other four substances to produce precipitation.
Example 3. The main components of water gas are carbon monoxide and H2 (containing a small amount of carbon dioxide and water vapor). A student verified the main components of water gas through the following experiment. Please answer the questions according to the following equipment.
The chemical equation of the reaction in 1 One kind of equipment is:
2. The substances contained in equipment B are:
3. The substances contained in equipment C are:
4. The phenomenon in device D is:
5. If the positions of equipment E and F are reversed, the consequences will be.
Solution: 1, CO2+2NaOH→Na2CO3+H2O.
2. Clarify limewater and check whether CO2 in water gas is eliminated.
3. Concentrated H2SO4. Black powder turns red 5. It cannot be proved that H2 exists in water gas.
Description: This is a comprehensive experimental ability question. Including the composition of the instrument, the inspection of substances, the observation of experimental phenomena and the writing of related chemical equations.
Comments: In this kind of experimental questions, the basic operation of the experiment, the connection of instruments, the design of experimental scheme, the organization and expression of language, and the integration of analysis, generalization, reasoning and inquiry of chemical knowledge were investigated. It emphasizes innovation consciousness and practical ability, the design and evaluation of experimental scheme, and the comprehensive process of students' participation and solving experimental problems. So as to cultivate students' scientific attitude and innovative spirit of solving problems through experiments and their ability to explore and solve chemical problems.
② Interdisciplinary synthesis
Example 1. A student did the following experiment: put a small ball that does not react with hydrochloric acid into a beaker containing dilute hydrochloric acid, and the ball was suspended on the liquid surface. Put some nails in the beaker until there are no more bubbles (ignoring the volume change of the solution). Compared with the beginning, the position of the ball ()
A. float B. stay the same C. sink D. sink to the bottom of the cup
Analysis: This question comprehensively examines the mass change of solution after the reaction between iron and acid and the knowledge about buoyancy in physics. Before nailing, the buoyancy of the ball is equal to its own gravity, that is, G=m? G = rho liquid? g？ In line V, after adding nails, the reaction takes place in the solution: that is, for every 56 parts of iron entering the solution, two parts of hydrogen escape from the solution. When the mass of the solution increases by 54 phr, the volume of the solution remains unchanged, but the density of the solution increases with the increase of the mass of the solution, and the gravity (m? G) It hasn't changed, so only row V has become smaller, so the ball is floating.
The answer is a.
Comments: The proposition of interdisciplinary knowledge integration is to cultivate students' interdisciplinary comprehensive problem-solving ability, adjust students' perspective of observing and solving problems, and face various problems in real society from an "integrated" perspective. It is of great significance to cultivate students' innovative spirit and practical ability and establish a scientific outlook.
③ situational information synthesis questions
Example 1. Three scientists from the United States and Japan won the 2000 Nobel Prize in chemistry for their research achievements in conducting organic polymer materials. In their related technology, they doped iodine into the polymer, which enhanced its conductivity by 107 times and had metallic conductivity. Iodine (I2) belongs to ()
A. metallic element B. nonmetallic element C. compound D. mixture
It is reported that in recent years, scientists have discovered a new energy source in the deep seabed such as Bermuda, which looks like ice and is also called combustible ice. Scientific research shows that combustible ice is actually methane hydrate (CH4? XH2O) is a solid substance formed by methane and water at low temperature and high pressure.
1. At present, the main gaseous pollutants discharged into the atmosphere are SO2, NO2, CO, etc. They mainly come from mineral combustion and industrial waste gas. Today, there are: ① combustible ice, ② hydrogen energy, ③ wind energy, ④ solar energy, ⑤ coal, ⑤ natural gas, ⑤ petroleum and other energy sources. Under normal circumstances, the group that generally does not cause air pollution is ().
A.①②③④⑥ B.②③④⑥⑦ C.①③④⑤⑥ D.①②③④⑤