Acid, alkali and salt are important knowledge of elemental compounds in junior middle school chemistry. The author found from the teaching that after teaching the contents of acid, alkali, salt, especially salt, students often complain: "There are too many things to remember, how much acid, how much alkali, and how much salt there is now …" Why does our class give students the impression that these chemical equations and chemical principles need to be memorized? How can we solve students' inner confusion? With these problems, the author thinks, explores and tries the teaching design of "carbonate" in the second lesson of Unit 11 of ninth grade chemistry subject 1 Salt in Life.

1 Instructional design concept

Chemistry comes from life, but traditional education separates science from life, making students fixed in a single "book world" or "scientific world", causing students to forget themselves and stay away from the "life world", so education has lost its fresh life. An important goal of the new curriculum reform is to make science education return from the scientific world to the life world, and regard science as the science in human life. Therefore, chemistry teaching in the new curriculum should strive to enter the students' life world and build a life-oriented classroom.

2 Analysis of the content of teaching materials

Judging from the compilation of the new textbook, it seems that the chemical properties of acid and alkali salts are weakening, but this does not mean that the chemical properties of acid and alkali salts are not needed. Some important chemical reactions and important reactivity are actually needed, and this knowledge is also an important basis for high school chemistry learning. However, if these reaction laws are taught too intensively and purely as in the old textbooks, it will inevitably cause difficulties for students' learning. What should we do? Pack salt-related knowledge, set off and run through life scenes and problems, let students feel the close connection between chemistry and daily life and production practice, effectively understand knowledge, and further strengthen the establishment of the basic chemical concept of "the nature of substances determines the use".

Three representative carbonates-calcium carbonate, sodium carbonate and sodium bicarbonate are introduced in the new textbook. For these three kinds of salts, there are not many contents in the introductory textbooks, especially the use of these three kinds of salts in life is only a few pictures or simple explanations. It can be seen that the textbook is nothing more than a "life example" that we can learn from, but there are also many realistic, meaningful and challenging materials in the colorful real life, which need us to further explore.

3 the determination of teaching objectives

Knowledge and skills: to understand the commonness of sodium carbonate, sodium bicarbonate and calcium carbonate in composition and their main uses in life; Master the inspection method of carbonate ion; Understand the outstanding contributions made by scientists in China.

Process and method: understanding carbonate from various perspectives such as nature and life; Through the exploration of property experiments, we can understand the commonness of carbonate, and then summarize the inspection methods of carbonate ions, guide students to contact the properties and uses of substances, so that students can learn to analyze and solve some simple practical problems related to chemistry and understand the basic chemical concept of "properties determine uses, and uses reflect properties". Through the process of experimental inquiry and problem discussion, students can learn to explore the essence of scientific thinking and experimental research methods from phenomena; Through the connection with real life, students can establish methods to solve daily problems by applying chemical knowledge.

Emotion, attitude and values: understand the chemical principles contained in chemical phenomena and examples in life, and cultivate students' awareness of learning and applying chemistry in life; Stimulate students' enthusiasm for learning and patriotism, and stimulate students' sense of responsibility and mission to revitalize the nation.

4 the concept of instructional design

Starting from the historical event of "Burning Yuanmingyuan", create a situation to arouse students' strong curiosity and high concern, and then lead to the protagonist of this class-carbonate, and then tightly buckle the two knowledge lines of "the nature and use of carbonate", constantly grasp the teaching opportunity, find the combination point and growth point of chemistry and life, integrate the study of chemical knowledge into related life phenomena and solve specific practical problems, so that students can understand chemical substances in real life situations.

5 Teaching process and analysis

5. 1 Reproduce history, perceive matter

(Photo introduction) Photo of Yuanmingyuan site.

Yuanmingyuan, known as the Garden of Ten Thousand Gardens, is a royal garden built by the working people in our country with sweat and blood. It contains many exquisite treasures, books and artistic masterpieces, and uses a lot of white marble and jade materials. Do you know what is the main component of white marble?

The students were surprised, curious and excited about this ingredient and asked each other. According to their life experience, they guessed that it was calcium carbonate. )

Could you please tell me the chemical formula of calcium carbonate? Often referred to as

White marble is one of the varieties of marble. Because it is as white as jade and extremely hard, it has been the first-class building material since ancient times. But there is a history that we should not forget! 1860, two robbers broke into the garden. They robbed, destroyed and set fire everywhere in the garden. Some magnificent buildings made of white marble were destroyed by the fire and broke into pieces.

The teacher deliberately "left blank" at the right time, and the students were immersed in grief and indignation. )

(The teacher took the opportunity to inspire) The burning of Yuanmingyuan has done us great harm, but we can never forget the lesson of history: we will be beaten if we fall behind. Every student here should cherish today's wonderful time and study hard.

(The teacher took the opportunity to contact with practice.) Its combustion actually contains a chemical principle. Why do those hard white marble stones break after being burned? Can you explain it by chemical principles?

The students are in high spirits, thinking actively, scrambling to answer and write chemical equations about the reaction principle. )

What are the general applications of this principle in our daily life and production?

(Student answers) Industrial carbon dioxide.

(Continue to ask) So how do we make carbon dioxide in the laboratory?

Students write chemical equations on the blackboard. )

[Analysis] Educator Suhomlinski said: "If teachers don't try to make students have a highly emotional and intellectually excited inner state, but do mental work without emotion, it will bring fatigue, and it is difficult for a tired mind to effectively absorb knowledge." The author shows the reappearance of real historical events through "Photographs of Yuanmingyuan Ruins" (here borrowed from the materials about Yuanmingyuan in the topic of "Utilization of Limestone" published by Shanghai Education Publishing House), sets appropriate situations to take warning, arouses students' appetite from the beginning, guides students to observe chemical phenomena in life from a chemical point of view, and understands the chemical principles contained therein, which narrows the distance between chemistry and life and stimulates students' long-term learning enthusiasm.

5.2 experimental inquiry, into life

(Question) Based on the principle that limestone and dilute hydrochloric acid generate carbon dioxide, we can divide CaCO3, the main component of limestone, into acid, alkali and salt.

(Student answers) Salt.

(Get to the point) Today, we will introduce two other common salts in life: sodium carbonate, with the chemical formula of Na2CO3, and sodium bicarbonate, with the chemical formula of NaHCO3.

(Students think 1) Please observe the similarity in composition of CaCO3, NazCO3 and NaHCO3.

(Students observe communication) all contain carbonate ions.

In fact, sodium bicarbonate NaHCO3 dissociates bicarbonate ions in aqueous solution first, and then further dissociates bicarbonate ions. Because all three salts contain carbonate ions, we call them carbonates.

(Student thinking 2) Will the chemical properties of these three salts be similar? What are the similar chemical properties?

Students actively speculate that it may react with acid to generate carbon dioxide ...

Students discuss in groups, explore the reaction law of carbonate and acid through experiments, and teachers patrol and guide. )

(Student report summary) The law of reaction between carbonate and acid: The salt containing carbonate ion or bicarbonate ion can react with hydrochloric acid to generate CO2 gas.

(Guide students to broaden their thinking) From three experiments, we can get inspiration. How to test whether a substance contains carbonate ions or bicarbonate ions?

(Student's summary) The method of testing carbonate ion or bicarbonate ion.

Students personally experience, explore and design experiments, which prove that the main component of egg shell is calcium carbonate, which contains carbonate ions. )

What substance can be used to replace the medicine in the above experiment at home?

(Students scramble to speak)

[Analysis] Chemical knowledge is closely related to life. Every time you learn a knowledge point, you should try to guide students to contact their real life, what they have seen and heard. Once they apply what they have learned, students' learning enthusiasm will be higher and their desire to try will be stronger, which will play an inestimable role in activating the classroom, extending the classroom, activating knowledge and developing their ability. With the background of "exploring the main components of eggshells", the author brought the application of carbonate ions and learning experimental methods into life, which made the experiment meaningful and the study of chemistry valuable.

5.3 come back to life. Learn for practice.

What other substances contain calcium carbonate in our life?

Students are talkative and speak freely, which complement each other. )

(The teacher supplemented and showed pictures) Substances containing calcium carbonate in daily life: pearls, shells, toothpaste, corals, grotesque caves, marble, white marble works, etc.

Calcium carbonate exists widely in life. Do you know what application it has in our life?

(Students communicate with each other) Uses: ① Making building materials (showing pictures of China watches and marble floors); (2) calcium supplementation, treatment of hyperacidity (show the label chart of related tablets.

(Students think about life) Do you know the principle of calcium carbonate to supplement calcium and treat hyperacidity?

Students suddenly realized that this was based on the reaction principle of calcium carbonate and hydrochloric acid in gastric acid. )

In addition to calcium carbonate, sodium bicarbonate can also be used to treat stomach acid.

(Showing pictures) Instructions for sodium bicarbonate tablets.

Students focus on the pictures and words of the courseware and analyze the principle of sodium bicarbonate in treating gastric acid. )

What other uses does sodium bicarbonate have besides treating hyperacidity?

(Projection) Sodium bicarbonate is used as baking powder.

Common name of sodium bicarbonate: baking soda.

(Students think about life) What role does sodium bicarbonate play in it?

(Information provided: The baking powder contains sodium bicarbonate and organic acid; A feature of puffed food such as steamed bread, bread and cakes is that there are many holes in the dough.

(Students analyze and judge according to the properties of carbonate just learned: the small hole was originally a small house where carbon dioxide lived. )

In addition to sodium bicarbonate, sodium carbonate can also be used as baking powder.

(Showing objects and projecting pictures) Convenient edible alkali packaging bag.

Sodium carbonate is widely used in washing, papermaking and glass production. Sodium carbonate is commonly known as soda ash, soda ash and oral alkali.

Students realize the practical application of sodium carbonate in industrial production and daily life. )

(Question) Sodium carbonate belongs to salt, but why is it commonly called soda ash?

The chemical properties of sodium carbonate extracted by students through life experience may be alkaline. )

(Experimental exploration) The phenolphthalein solution was dropped into the sodium carbonate solution.

(Observing and thinking) What inspiration can you get from this experiment?

It suddenly dawned on the students that salt solution is not always neutral.

(Introduction to Chemical History) The Pioneer of China Alkali Industry-Hou Deeds

(Group cooperation) Take sodium carbonate, which is common in our life, as an example, and combine the knowledge about the properties of acid and alkali that we have learned before to summarize the chemical properties of salt.

The teacher supplemented the experiment to improve the properties related to salt. )

(Feedback exercise) Omission

(Perception and harvest) Tell me about your harvest in this class? How do you feel?

Students speak freely: chemistry is by my side; Chemistry is everywhere, everywhere ...)

[Analysis] Returning to life from chemistry is the sublimation of reason, the application of knowledge, the improvement of ability and a successful experience.

6 Teaching reflection

Imagine that if our teaching is divorced from the students' life world, such teaching will inevitably make the colorful chemistry world look so pale and rigid. Over time, students will find chemistry learning so boring that they can't see the value of learning it. They just think it's a bunch of symbols that need to be memorized desperately. Chemistry shouldn't just be a rigid knowledge teaching, and it can't stick to the rules and follow the book. Chemistry comes from life and serves real life. Chemistry teaching should follow the ideas of coming from life, living in life and applying to life. Only in this way can students construct knowledge comprehensively, truly and efficiently, activate the survival and application of knowledge, and maximize the spirituality of life. Only in this way can chemistry learning be truly integrated into the process of students' life growth.

refer to

[1] Liu, middle school chemistry teaching reference, 2006, (5): 1

[2] Wei Wen, Chen Yi, Lu Zhen, Chemistry Teaching, 2006, (7): 28-29.

[3] Wang, classroom teaching towards the life world, Beijing: Education Science Press, 2007: 232-237.

[4] Hui-juan Li, middle school chemistry teaching reference, 2009, (9): 24-27.