Cases of ninth grade chemistry teaching
First of all, talk about textbooks.
This lesson is selected from the ninth grade experimental textbook of compulsory education curriculum standard, Unit 11, Lesson 2, Salt in Life. Through the last class, students learned about the common salt in life and its main uses, and learned about the detection methods of carbonate ions and some chemical properties of salt. On this basis, this lesson mainly explores the conditions and occurrence of learning double decomposition reaction. According to the requirements of chemistry curriculum standards and the characteristics of chemistry, it can be seen that metathesis reaction is a very important knowledge content, which requires students to master the concept and conditions of metathesis reaction and the solubility of acid, alkali and salt. Learn to judge the type of metathesis reaction; Write the chemical equation of metathesis reaction correctly.
Before learning this lesson, students already know the chemical properties of common acids, bases and salts and the reactions of combination, decomposition and replacement, but they can't judge the types of reactions among acids, bases and salts, which leads to doubts. Therefore, learning the double decomposition reaction of this lesson will make students familiar with the teaching content, relieve students' strange tension about new knowledge and keep them relaxed and good. The overall arrangement of teaching materials reflects the hierarchy and systematicness of complex decomposition reaction knowledge, permeates the concept of easy first, then difficult, step by step, and conforms to the cognitive law of junior high school students.
As a "tall building" in chemical terms, metathesis reaction not only needs the assistance of basic chemical terms such as element symbols, valence and chemical formula writing, but also needs the support of acid-base solubility and metathesis reaction conditions. Therefore, skillfully and accurately writing the chemical equation of double decomposition reaction plays an important role in learning chemistry knowledge in junior middle school and continuing to study chemistry in the future, and is also of great significance to improving students' comprehensive literacy in chemistry learning.
Second, say the goal.
According to the curriculum standards, teaching materials and the actual situation of students in our college, the teaching objectives set by our college are as follows:
Knowledge and skills
1, to understand the metathesis reaction, we can judge whether some common reactions between acids, bases and salts can occur according to the conditions of metathesis reaction.
2. Learn to write the chemical equation of double decomposition reaction correctly.
Process and method
1, learn to use observation, experiment and other methods to obtain information, and can express relevant information in words and chemical language.
2. Learn to use the methods of classification and comparison to summarize the experimental information, induce the reaction law, form the concept of "double decomposition reaction", and understand the "conditions of double decomposition reaction" and "solubility of acid and alkali salts" by writing the chemical equation of double decomposition reaction.
Emotional attitudes and values
Through the study of double decomposition reaction, students have strengthened their ability to master the basic knowledge systematically and flexibly, initially formed a relatively systematic knowledge network, felt the importance of the interconnection of knowledge, and deeply realized that chemistry is everywhere in life.
Third, talk about learning.
"Chemistry Curriculum Standard" points out: "Students are the main body of learning and development, and chemistry teaching must fully stimulate students' initiative and enterprising spirit according to their physical and mental development and the characteristics of chemistry learning, and advocate independent, cooperative and inquiry learning methods". According to this requirement, the teaching process of this topic mainly pays attention to the following aspects:
(1) Pay attention to students' existing knowledge and experience.
The knowledge base required by this topic, such as the composition characteristics of salt, the chemical properties of salt, the solubility of acid, alkali and salt, etc. , which is already available for students. However, from the situation reflected in the students' learning process, there are still several problems: the foundation is not solid, the knowledge is not systematic, the application is not flexible, and the students' foundation in our school is relatively weak. These factors directly restrict the improvement and development of students' chemistry learning in the future. Therefore, the teaching of this course should be consolidated and improved, systematic and gradual, so that students can form learning ideas and methods about the content of metathesis reaction in the process of recall, comparison and induction.
(2) Pay attention to students' learning methods and skills.
Image perception and systematic induction are important methods to learn this topic well. In teaching, different teaching methods are adopted to fully mobilize students' senses and improve their understanding of knowledge; Different practice methods are adopted to consolidate the concept and occurrence conditions of complex decomposition reaction from different angles, improve students' ability of systematic induction and comprehensive application of knowledge, broaden students' learning ideas and methods, and cultivate students' ability of system construction.
(3) Pay attention to students' personality development and group promotion.
The knowledge needed for this topic is a summary and extension of the knowledge learned. Therefore, students with poor basic knowledge should be allowed to exchange answers and give corresponding positive comments to improve their self-confidence in chemistry learning. For problems with certain comprehensive difficulty, let students with relatively good foundation discuss and communicate, encourage them to think diligently and dare to question, form a learning atmosphere that is good at letting a hundred schools of thought contend, and actively guide them to cooperate, communicate and explore. Let all kinds of students gain something, improve and develop through the study of this course.
Fourth, talk about the teaching process
1, project introduction
Show the teaching pictures of "Common Salt in Life", draw out the composition characteristics and chemical properties of salt, analyze and summarize the chemical equation characteristics of common acids and salts, and draw out the concept of double decomposition reaction.
2, the image is intuitive, breaking through difficulties.
Students in Grade Three have gained some understanding and perception. In order to visualize abstract questions, different forms are adopted in the teaching process to fully mobilize students' learning organs and improve their understanding and perception of knowledge. Through flash animation, how to dynamically show the concept of "component exchange", strengthen the understanding of the essence of metathesis reaction from the perspective of "vision and hearing", break through the teaching difficulties, and improve students' accurate writing ability of metathesis reaction chemical equations. Therefore, I designed two links to break through the difficulties:
The first part, the key breakthrough: understanding the essence of metathesis reaction is the teaching difficulty of this course. On the basis of students' proficiency in writing common chemical equations of acid and salt, alkali and salt, flash animation is played to dynamically demonstrate the "exchange components" of compounds in the concept of metathesis reaction, so as to strengthen the understanding of the nature of metathesis reaction from the perspective of "vision and hearing", break through the teaching difficulties and improve students' accurate writing ability of metathesis reaction chemical equations.
Link 2, Breakthrough of Difficulties: Students conclude that the reactions between acid and salt, Na2CO3 and Ca(OH)2, and acid and alkali belong to double decomposition reactions. Through cooperative exploration experiments, NaOH can react with CuSO4 or FeCl3 _ 3, while NaCl can react with AgNO3 _ 3, Na _ 2SO _ 4 and BaCl2 _ 2, all of which belong to double decomposition reaction and have the characteristics of these known reaction products. Summarize the conditions of double decomposition reaction, play flash animation, vividly and dynamically demonstrate the conditions of double decomposition reaction from a microscopic point of view, deepen students' judgment on whether the conditions of double decomposition reaction can occur, and break through the teaching difficulties.
Step 3 summarize
By comparing the chemical equation of salt with the characteristics of displacement reaction, the concept and types of displacement reaction are summarized.
4. Experimental inquiry
Through the experiments of CuSO4 _ 4 and NaOH, FeCL3 _ 3 _ 3 and NaOH, AgNO3 _ 3 _ 3 and NaCl, Na _ 2SO _ 4 and BaCl2 _ 2, we observed, analyzed and obtained the phenomena that alkali reacts with salt, and salt reacts with salt to generate precipitation, so as to have a perceptual understanding of the conditions of double decomposition reaction, and to transform perceptual knowledge into theoretical understanding and break through the difficulties. At the same time, let students further feel that the writing of chemical equations must "respect objective facts" and "chemical knowledge is based on experiments" to improve their understanding of metathesis reaction conditions.
5. Expansion and improvement
Through specific exercises in teaching design, students' knowledge system and comprehensive application ability are enhanced while their knowledge of double decomposition reaction is consolidated, and their ability to accurately write chemical equations of double decomposition reaction is improved.
The design of exercises is from easy to difficult, which embodies the hierarchical and systematic knowledge of double decomposition reaction, conforms to the cognitive law of junior high school students, permeates the connection between chemical knowledge and life, and makes students feel that chemistry is around us in the process of analyzing and solving problems, and chemistry is everywhere in life.
Five, the teaching design of this course inspired me.
I think the process of instructional design is the process of dialogue among teachers, textbooks and students, which is not only the process of educating students, but also the process of mutual education between teachers and students, and it is also the process of self-education and reflection of teachers. Only in this way can we find our own "weaknesses" and strive to tap our own "bright spots".
Cases of ninth grade chemistry teaching
First, import
Teacher: Last class, we learned about primary batteries. Please recall, what are the conditions for forming a primary battery?
Health: (thinking) the conditions for the formation of primary batteries: two electrodes with different activities; Electrolyte solution;
Health: form a closed loop; Spontaneous redox reaction.
Second, the new teaching
Teacher: [Projection display] is shown in the figure below. Observe the experimental phenomenon and answer: the change of ammeter pointer. What happened to the carbon rod? What happened at the poles?
(biological observation phenomenon)
Health: 1. The ammeter pointer deviates;
Health: 2. There is a red substance on the carbon rod.
Teacher: Please write down the electrode reaction here.
Health: Iron is the negative electrode and carbon rod is the positive electrode.
Raw:Fe:Fe-2e = Fe2+ oxidation reaction; C: Cu2++2e = Cu reduction reaction; Total reaction equation: Fe+Cu2+=Fe2++Cu.
Teacher: There are three experiments designed here. Please experiment in groups and observe the experimental phenomena, accurately record the experimental phenomena and report the experimental results.
[Projection display] 1. Insert two carbon rods into a small beaker filled with CuCl2 solution, soak for a while, take out the carbon rods, and observe the surface phenomenon of the carbon rods (Figure1); 2. After connecting the carbon rods with wires, immerse them in CuCl2 solution for a period of time, take out the carbon rods, and observe the surface changes of the carbon rods (Figure 2); 3. Two carbon rods immersed in copper chloride solution are respectively connected with the anode and cathode of DC power supply. After connecting for a period of time, observe the phenomena on the two poles, and check the generated gas with wet KI- starch test paper (Figure 3).
Teacher: In this process, please be sure to standardize the operation and pay attention to safety.
Health: there was no obvious change in carbon rods in the first two experiments;
Health: In the third experiment, it was found that red solid matter was precipitated on the carbon rod connected to the negative electrode of the power supply.
Health: the carbon rod with one end connected to the positive electrode of the power supply produces gas, which makes the wet starch -KI test paper blue.
All students: analyze and make judgments. The red substance is copper, and the yellow-green gas that makes wet starch -KI test paper blue is chlorine.
Anode product-chlorine gas (Cl2); Cathode product-copper (Cu)
Teacher: Why did this happen? [Hint] Discussion outline
[Projection display]
1. What ions were present in the solution before electrification? How do these ions move?
2. How does the original ion movement change after the direct current is switched on?
3. What happened to the two poles?
Health: (discussion and analysis)
Cu2+, Cl-, H+ and OH- in 1. solution move freely before electrification.
2. After electrifying, positively charged Cu2+ and H+ move to the cathode; The negatively charged Cl- and OH- move towards the anode.
3. The electrons of Cu2+at the cathode become elemental Cu, and Cl- loses electrons at the anode and becomes Cl2.
Teacher: [summing up the blackboard]
Before power-on: cucl2 = Cu2++2cl-; H2OH++OH- free motion
After electrification: anode: 2cl-2e = Cl2 ↑ oxidation reaction; Cathode: Cu2 ++ 2e = copper reduction reaction
Total reaction chemical equation: CuCl2=Cu+Cl2↑.
[Summary] Popular notation, using homophony. Anode-oxygen reaction
Teacher: How do electrons form a closed loop during electrolysis? Please see page 64 of the textbook to summarize the electron flow.
Direction.
Health: negative electrode of power supply → cathode of electrolytic cell → electrolyte → anode of electrolytic cell → positive electrode of power supply.
Teacher: That's right. Let's summarize.
Teachers and students: The direction of electrons is opposite to the direction of current, flowing from the negative pole of power supply to the cathode of electrolytic cell and Cu2+ near the cathode.
Electrons obtained at the cathode are reduced to copper, anions and cations in the solution move directionally, and Cl- near the anode loses electrons at the anode and is oxidized.
Into chlorine atoms. Chlorine atoms combine to form chlorine molecules, and the lost electrons flow back from the anode to the anode of the power supply, thus forming a closed
closed circuit
Teacher: What is the relationship between the conductivity of electrolyte solution and the ionization of solution?
Health: ionization first, then electrolysis. Ionization does not require electricity, and electrolysis is based on ionization.
Teacher: Now, let's finish the projection display table.
Student: (Each student completes one item and fills in this form with * * *. )
two
First, the guidance class
China Tiangong-1 and Shenzhou-10 manned missions were a complete success. You can see that all spacecraft and satellites have a pair of huge solar panels like wings. Do you know what it does? Have you ever wondered where the power comes from when the spacecraft runs to the shadow area where the sun can't shine?
Video: Engineers' Solutions
Second, people-oriented learning.
Task 1: According to the schematic diagram of the electrolyzer, read pages 79-80 of the textbook to solve the following problems:
1, discharged from hospital:
2, electrolysis (definition):
3. Electrolytic cell:
4. Elements of electrolytic cell:
Task 2 Adding electrolyte to water can enhance the conductivity of water, but will it affect the reaction of electrolytic water? We answer this question by exploring experiments.
The principle of electrolysis was explored experimentally. Electrolyzing copper chloride solution with graphite as electrode.
Problem-oriented autonomous learning
1, write the ionization equation of electrolyte:
The ions existing in the analytical solution are:
2. After electrifying, the movement direction of ions: towards the cathode.
Move towards the anode.
Common learning
3. Predict the electrolytic products and design the experimental scheme.
4. Experimental records:
Please use the instruments and reagents on the desktop to prove your guess. Is the experimental phenomenon consistent with your guess? Any new conclusions and ideas?
Experimental phenomenon
Electrode reactions and reaction types
positive electrode
negative pole
Electrolytic copper chloride
Total reaction of
conclusion
Projection display communication
1. What experimental phenomena have you observed?
2. What is the reaction between anode and cathode?
3. What experimental conclusion did you get?
Thoughts on comparison between primary battery and electrolytic cell
device category
primary battery
electrolytic cell
Electrode name
Electrode reaction
energy transformation
Will the reaction be spontaneous?
Thirdly, the lead contact is detected.
1. Determine whether the following equipment belongs to the electrolytic cell:
Accelerated business collection and delivery system (adopted by the United States post office)
2 The following statement about electrolytic cell is incorrect ()
A. An electrolytic cell is a device that converts electrical energy into chemical energy.
In an electrolytic cell, anions move to the cathode and cations move to the anode.
C, an anode connected with the positive pole of the power supply in the electrolytic cell undergoes oxidation reaction.
D. The conductive process of electrolyte solution is the electrolytic process of electrolyte solution.
3. In the electrode reaction of primary battery and electrolytic cell, it belongs to oxidation reaction or reduction reaction ().
The reaction between the anode of the galvanic cell and the anode of the electrolytic cell;
The reaction between the anode of a galvanic cell and the cathode of an electrolytic cell.
Reaction between cathode of galvanic cell and anode of electrolytic cell
Reaction between cathode of galvanic cell and cathode of electrolytic cell.
Asian Development Bank.
Reflection summary
Cases of ninth grade chemistry teaching
I. Guiding ideology
With hope and expectation, the new semester is coming. This semester, under the guidance of the new concept of "curriculum reform" and the new "curriculum standards", I will continue to take the development of students as the foundation and work together with Qixin to implement all the work assigned to me by the school, update teaching concepts, improve teaching quality and standardize teaching process. Refine your own teaching level while doing scientific research, help students develop all aspects of quality, and at the same time raise their professional level to a new level.
Second, the analysis of students' basic situation
Chemistry is a new course just opened in the ninth grade, which has more contact with life and students' enthusiasm for learning is also relatively high. Teachers should guide correctly in order to get good grades in the senior high school entrance examination. During this period, I was a chemistry teaching task in Class 6, Grade 9, and the students' level varied greatly. Therefore, we should teach students in accordance with their aptitude in this semester's teaching work. In teaching, it is necessary to improve the teaching progress and knowledge difficulty, and cultivate students who can participate in the competition. In the face of students with poor foundation, we should grasp the foundation, teaching methods and teaching rules, learn more and practice more, so that students' chemistry scores can meet the requirements of the school and clear the way for the comprehensive victory of the senior high school entrance examination.
Third, the overall goal of teaching
The chemistry course in compulsory education stage aims to improve students' scientific literacy, stimulate students' interest in learning chemistry, help students understand the basic process and methods of scientific inquiry, cultivate students' scientific inquiry ability, and enable students to acquire the basic knowledge and skills of chemistry needed for further study and development;
Specific teaching objectives
Through the study of chemistry course, students are mainly developed in the following two aspects.
Knowledge and skills
1. Understand the composition, properties and applications of some common substances around us, which can be described in simple chemical language.
2. Form some basic chemical concepts, understand the microstructure of substances, understand the basic characteristics of chemical changes, and understand the relationship between the properties and uses of substances.
3. Understand the relationship among chemistry, society and technology, and analyze related simple problems on this basis.
4. Initially form basic chemical experiment skills, and be able to design and complete some simple chemical experiments.
5. By learning and mastering junior high school chemistry knowledge, lay a solid foundation for future senior high school study.
Process and method
1. Understand the significance and basic process of scientific inquiry, ask questions and conduct preliminary inquiry activities.
2. Initially learn to use observation, experiments and other methods to obtain information, and can use words, charts and chemical language to express relevant information, and initially learn to use methods such as comparison, classification, induction and generalization to process the obtained information.
3. We can analyze chemical phenomena from the viewpoint of change and connection and solve some simple chemical problems.
4. Be able to actively communicate and discuss with others, clearly express their views, and gradually form good study habits and methods.
Fourth, specific measures.
(1) Strengthening experimental teaching
Chemistry is a subject based on experiments. Experimental teaching can stimulate students' interest in learning chemistry, help them to form concepts, acquire knowledge and skills, cultivate their observation and experimental ability, and also help to cultivate a realistic and serious scientific attitude and scientific learning methods. Therefore, strengthening experimental teaching is an important link to improve the quality of chemistry teaching. In teaching, we should resolutely prevent the bias of emphasizing only lectures and ignoring experiments. In experimental teaching, we should attach importance to safety education, educate students to care for instruments and save drugs.
(2) Actively carry out extracurricular activities in chemistry.
Organizing and guiding students to carry out extracurricular activities in chemistry is very beneficial to improve students' interest in learning chemistry, broaden students' knowledge horizons, cultivate and develop students' abilities and give full play to students' intelligence. The content and methods of extracurricular activities should be flexible and diverse. In the content of activities, it can include connecting with society, connecting with life, combining with the development of science and technology and the history of chemistry, and expanding the knowledge learned in class. Activities can take the form of doing interesting experiments, holding knowledge lectures, chemistry competitions and special discussions, and organizing students to make teaching AIDS and visit. When organizing extracurricular activities, we should give full play to students' specialties and cultivate their innovative spirit.
(3) Strengthen the teaching of chemical terms.
Element symbols, chemical formulas and chemical equations are chemical terms used to express the composition and change of substances, and are important tools for learning chemistry. In teaching, students should learn the corresponding chemical terms by combining physical objects and chemical reactions, and associate the corresponding physical objects and chemical reactions by combining chemical terms. In this way, it is not only conducive to students' memory, but also conducive to deepening the understanding of the meaning of chemical terms. We should also pay attention to the decentralized teaching of chemical terms, so that students can gradually master these important tools for learning chemistry through lively and interesting learning activities and planned exercises.
(4) Pay attention to the teaching of the knowledge of elemental compounds.
The knowledge of elemental compounds is very important for students to lay a good foundation for chemistry learning. In order to enable students to learn the knowledge of elemental compounds well, we should pay attention to close contact with practice, strengthen intuitive teaching, experimental teaching and audio-visual teaching, so that students can contact more physical objects and do more experiments to increase their perceptual knowledge. Various ways should be taken to help them remember the important knowledge of elemental compounds on the basis of understanding. After students gradually master some knowledge of elemental compounds, teachers should pay attention to guiding students to understand the internal relationship between elemental compounds, let students understand the relationship between the properties, preparation methods and uses of elemental compounds, and pay attention to strengthening the guiding role of basic concepts and principles of chemistry in learning elemental compounds.
(5) Carefully organize the testing and assessment of each unit.
The study of chemical knowledge is also a gradual process, and many basic theoretical knowledge such as concepts, definitions, element symbols, chemical equations, etc. Need a lot of recitation to prepare for future study. Therefore, we should pay attention to this aspect every time we take exams such as weekly exams and monthly exams, so that students can pass them one by one.
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