Teaching objectives of ninth grade chemistry "Law of Conservation of Quality" teaching plan published by People's Education Press
learning target
1. Understand the concept of chemical equations.
2. Know the meaning of chemical equations.
3. Understand the reading of chemical equations.
Emphasis and difficulty in teaching
Important and difficult
1. Significance of chemical equation expression.
2. How to read chemical equations?
teaching process
Learning content-the definition and significance of chemical equations
Study Guide
Read the relevant content on page 96 of the textbook and complete the following blanks.
1. The formula of chemical reaction expressed by chemical formula is called chemical equation. In chemical equations, the left side of the equal sign represents reactants, the right side of the equal sign represents products, the reaction conditions are marked above the equal sign, and the equal sign is pronounced as generation. +? Reading and.
2. The meaning of chemical equation
Discussion and communication
How to find the mass ratio of each substance in the chemical equation?
Warm inspiration
The mass ratio of each substance = relative molecular mass? The ratio of the number of molecules.
The number of particles is the measured number before the chemical formula.
In chemical reactions, what is reduced is the reactant and what is increased is the product.
Principal induction
The mass ratio of each substance in a chemical equation is the ratio of the product of the relative molecular mass of each substance in the chemical equation and the stoichiometric number before the chemical formula. Generally speaking, the quality ratio is not simplified as the simplest ratio, but it can be simplified when solving fill-in-the-blank problems.
Feedback exercise
A.4P+5O22P2O5
B. Carbon+carbon dioxide
C. Sulfur+sulfur dioxide
D.2H2+O22H2O
2. Chemical equation is one of the important tools for learning chemistry. According to the chemical equation can't get the information is (D)
A. reactants and products in the reaction
B. mass ratio of reactants and products
C. Conditions required for the reaction to occur
D. the speed of chemical reaction
3. In a closed container, after the four substances X, Y, Z and W fully react under certain conditions, the mass of each substance before and after the reaction is measured in the table below. What is wrong in the following statement is (d).
A. the reaction is a decomposition reaction.
B.x may be the catalyst for this reaction.
The mass ratio of C, Y and Z is 9∶8.
D the mass of x after the reaction is 0g.
Learning content 2 Reading of chemical equations
Study Guide
Read the relevant content on page 96 of the textbook and complete the following blanks.
The pronunciation of S+O2SO2 includes three aspects:
Qualitative aspect: sulfur and oxygen generate sulfur dioxide when ignited.
In terms of quantity, 32 parts of sulfur and 32 parts of oxygen generate 64 parts of sulfur dioxide when ignited.
Particles: 1 sulfur atom and 1 oxygen molecule generate 1 sulfur dioxide molecule when ignited.
Feedback exercise
1. The statement about the reaction of C+O2CO2 is correct (D).
A. carbon plus oxygen ignition equals carbon dioxide.
B carbon atoms and oxygen molecules react to generate carbon dioxide when ignited.
C. A mass of carbon and a mass of oxygen react under the ignition condition to generate a mass of carbon dioxide.
D. carbon and oxygen react under ignition conditions to generate carbon dioxide.
2. The chemical reaction process of hydrogen and oxygen is shown in the following figure.
Try to answer the following questions:
(1) Write the chemical equation 2H2+O22H2O for this reaction.
(2) Besides the meaning of the chemical equation itself, what information can you get from the above picture? (just write two)
① There is no change in atomic species before and after the reaction;
② The number of atoms did not change before and after the reaction.
Teaching objectives of teaching design of the law of conservation of mass
(1) Knowledge and skills:
1, understand the law of conservation of mass and the reasons for conservation;
2. Understand the meaning of chemical equations.
(2) Process and method:
1, through the analysis of the nature of chemical reaction and the reason of mass conservation, cultivate students' ability of studying problems and logical reasoning;
2. Through the observation and operation of the experiment, cultivate students' hands-on experimental ability and observation and analysis ability;
3. Make students understand the significance and basic process of scientific inquiry, ask questions and carry out inquiry activities.
(3) Emotion, attitude and values:
1, to stimulate students' curiosity and desire to explore chemical phenomena in real life, and to stimulate students' interest in learning chemistry;
2. Cultivate students' dialectical materialistic views through experimental determination of the quality of reactants and products in chemical reactions;
3. Cultivate students' sense of cooperation and the scientific spirit of being diligent in thinking, rigorous and pragmatic, brave in practice and innovation.
Emphasis and difficulty in teaching
Teaching emphasis: understanding the law of conservation of mass through experimental exploration.
Difficulties in teaching: From a microscopic point of view, we know that the types and quantities of atoms have not increased or decreased before and after the chemical reaction.
teaching process
The new curriculum introduces and recalls some chemical changes in life and analyzes their quality changes. Such as coal quality (fill in? Reduce? 、? Increase? Or? The same? )? What is the quality of iron after rusting?
Ask whether the quality of a substance changes before and after chemical changes.
The relationship between the total mass of reactants and the total mass of products was explored experimentally.
Put forward a hypothesis: the total mass of reactants and the total mass of products.
a、gt； B,<c, = D, sometimes >, sometimes.
Design an experiment to test the hypothesis:
(Discuss) What experiment is chosen to test the hypothesis? (emphasize that there is a chemical change and a chemical reaction has taken place. )
(Design experiment) 1, white phosphorus+oxygen to ignite phosphorus pentoxide.
2. Iron+copper sulfate+ferrous sulfate
(Group discussion) 1, experimental purpose, experimental principle (guiding students to pay attention to the state of matter and think in combination with phenomena)
2. What experimental instruments and equipment are selected?
3. Main operation steps
(Demonstration) White phosphorus burns in the air (pay attention to the preservation method of white phosphorus)
(Discussion) 1, the function of glass tube (these may be the difference between the device designed by students and the demonstration device)
2. Why should the bottom of the container be covered with fine sand?
3. What is the function of tying a small balloon at the top of the glass tube?
4. Why should the whole set of instruments and equipment be sealed?
(Student experiment) Nails react with copper sulfate solution.
Describe the law of conservation of mass
The airtightness of the two experimental devices is compared, and the reasons are analyzed from the state of the material.
Discussion and communication
Activities and inquiry 1. When a student was doing a candle burning experiment, he completely absorbed the generated water and carbon dioxide with an adsorbent. As a result, he found that the quality had increased. Can you explain it to him? Do you think this reaction also follows the law of conservation of mass?
Think about why quality is conserved. Analyze from a microscopic point of view.
Animated demonstration courseware of charged decomposition of water, discussion.
Analysis of recombination of molecular splitting atoms and molecular aggregation substances
Summarize the microscopic essence of the law of conservation of mass-atomic three invariants.
The type of atom has not changed; The type of the reference element has not changed.
The number of atoms does not increase or decrease before and after chemical reaction;
The mass of the atom has not changed.
How long does it take to create a situation from 1 to 10000? Ask a classmate to demonstrate on the blackboard how to write 1 ~ 2s.
Tell me this is a brain teaser. Just add four zeros after 1, which is a shortcut. In fact, chemistry learning sometimes has shortcuts.
Question: What are the known chemical reactions?
Take the chemical reaction of sulfur burning in oxygen as an example. What are the ways to express it?
Students' answers may be: 1, sulfur burns in oxygen to produce sulfur dioxide;
2, sulfur+oxygen point sulfur dioxide
3, sulfur+oxygen sulfur dioxide
Which expression is the best? Where's the good news? (Guide the students to find out the reasons, and make them feel that they can know what kind of reaction is described in the third way without any hint. Pave the way for meaning)
Simple, easy to write, can clearly express the reaction, is the international common language.
The most striking feature of the third representation is that the chemical formula is used instead of the substance name. Using chemical formulas to represent chemical reactions like this is the shortcut chemical equation we are going to learn today.
Reading 2, chemical equations
Discuss the significance of imitating the chemical equation of carbon combustion in textbooks, and discuss the significance of the chemical equation of sulfur combustion in groups.
Summarize the meaning expressed by chemical equations:
1 represents reactants, products and reaction conditions;
2. Represents the mass ratio of reactants and products;
3, said the relative number of particles involved in the reaction.
Emphasize? +? The pronunciation of is different from that of mathematical symbols.
Explain reaction phenomena and colors of substances.
light the fire
Exercise How to calculate the mass relationship between reactants and products for the reaction of 4p+5o2 = = = 2p2o5? (Prompt students the meaning of symbols)
It is pointed out that: ① when calculating the mass ratio of reactants to products, the relative molecular mass of reactants should be multiplied by the stoichiometric number in front of each substance;
(2) Reduce the mass of reactants and products in the same proportion.
Note: The total mass of each substance before the reaction is equal to the total mass of each substance after the reaction, and the law of conservation of mass is observed. (Paving the way for Writing Chemical Equation Balance in Topic 2)
Summarizing chemical equations, like element symbols and chemical formulas, is a tool for learning chemistry and is of great significance.