The content of this topic runs through the whole book, which is not only an important material to complete the enlightenment education of chemistry in the basic education stage, but also an important basic knowledge of chemistry in junior high school. The content about the composition, properties and uses of substances also provides students with the subject of experimental exploration. This theme combines students' life experience, provides vivid and colorful chemical substances, and designs interesting inquiry activities, which is helpful to stimulate students' interest in learning chemistry and is very beneficial to cultivate students' material view and rational use of substances.
In a sense, "chemical substances around us" is an important carrier of learning junior high school chemistry and an important part of junior high school chemistry content. However, we can't only look at this part from the perspective of elemental knowledge, nor can we focus on the memory of material composition, properties, preparation methods, uses and other knowledge. While learning this knowledge, students should get a preliminary understanding of the methods of studying the composition, properties and changes of substances, gain personal experience of exploring substances and their changes, enjoy the fun of exploring substances, and realize the important significance of studying chemical substances around them in improving human life and quality and promoting social development.
2. A brief description of the learning content.
Air, oxygen, carbon dioxide and water are chemicals that students often come into contact with in life and society. In the courses of primary school nature, junior high school biology and junior high school physics, students have a certain understanding of these substances. Choosing "the substances around us" as the material of chemistry enlightenment education can help students further understand the substances in nature and their changes from the perspective of chemistry, and understand their close relationship with human beings. Because of their familiarity with the content, students are kind and easy to understand and accept. The experimental inquiry activities needed to learn this knowledge are convenient to obtain materials, simple and intuitive to operate, and suitable for beginners.
It is worth noting that although students are familiar with these substances, they lack in-depth understanding and have never studied them from a chemical point of view. It is a meaningful job to understand this knowledge through exploration. Teachers should carefully understand the learning objectives, grasp the teaching requirements, pay attention to creating learning situations, and carefully design teaching procedures and student activities.
Air around the earth: the composition of air; The main properties and uses of oxygen and carbon dioxide and their important roles in human life; Laboratory preparation of carbon dioxide; Circulation of oxygen and carbon in nature.
Composition of water; The difference between some natural water (seawater, hard water and mineral water) and pure water, water purification and water utilization.
3. Teaching strategies and methods
(1) Create learning scenarios for students with rich materials to stimulate students' interest in learning and guide them to learn actively.
Remind teachers to use various situations in teaching, guide students to find problems from real situations, learn actively and vividly through activities and exploration, strengthen practical links, and care about nature and society. Students can activate accumulated experience, reason and emotional experience in situational learning, which is beneficial to the study of knowledge, skills and thinking methods.
(2) Design inquiry activities suitable for students, and learn basic chemical knowledge and experimental skills through inquiry. This topic involves a lot of content, and a lot of knowledge can be learned directly through experimental inquiry. It is very effective to improve students' ability to solve practical problems.
(3) Make full use of various curriculum resources to cultivate students' practical ability.
For example, investigate the air and water pollution situation in the area where the school is located and put forward suggestions for governance; Understand the reserves, development and utilization of chemical mineral resources in the school area.
4. Problems that should be paid attention to in teaching.
(1) Change the current situation that teaching is divorced from the reality of production and life, reverse the tendency of simply explaining the composition, nature, changes and uses of substances, and emphasize introducing the knowledge of substances and their changes from real life scenes and natural phenomena as well as students' life experiences, so that the teaching process becomes a process for students to understand natural phenomena and social development from a chemical perspective.
(2) Change the teaching method that pays too much attention to the clue memory and retelling of the composition, nature, change and use of substances, and emphasize the "discovery" and "induction" of substances and their changing knowledge through students' independent scientific inquiry.
(3) Change the tendency of attaching importance to experiment, theory, actual situation and book knowledge, strengthen experiment design and operation, and attach importance to creating teaching situations.
(4) To evaluate the learning of this topic, we should pay attention to changing the traditional way of memorizing materials' properties, preparation methods, uses and other knowledge and proficiency, and comprehensively evaluate the learning objectives from three dimensions.
5. Classroom suggestions
7-9 class hours
Section 1 Air composed of various substances
Zhenjiang Experimental School Zhang Lihua
First, the teaching objectives
Knowledge and skills:
1. Understand the concepts of purity and mixture, and know that air is a mixture. According to their characteristics, learn to judge some simple purity and mixture.
2. Understand the composition of air and the use of nitrogen and rare gases.
Process and method:
1. Through my career, I have a certain understanding of the volume content of oxygen in the air.
Emotional value:
1. Get to know the air quality. Understand the source of air pollution and the importance of eliminating air pollution, and strengthen environmental awareness.
Two. Important and difficult
1. Use of nitrogen and rare gases
2. Characteristics of pure substances and mixtures
Three. Class hours: one class hour.
4. Teaching methods: classroom explanation and experimental guidance.
Teaching design of verb (abbreviation of verb)
Introduction:
1. experiment: determination of oxygen volume content in air
Observe the experimental phenomena carefully, think, discuss and answer the following questions:
(1) What gas will be consumed when red phosphorus is burned in a gas container?
(2) Red phosphorus failed to burn completely in the gas container. What does this mean?
(3) Is the remaining gas in the container oxygen?
(4) Why can water, which accounts for about15 of the flat volume of the machine, be sucked into the gas container after the water stop clamp is opened?
(5) What other experiments can be designed to determine the volume content of oxygen in the air?
Briefly introduce the discovery of air composition.
Discussion summary:
Air is a mixture. Among them, oxygen accounts for about 1/5 of the total air volume. Residual gas can not support combustion, accounting for about 4/5 of the total air volume.
2. For example, the concept of mixture.
For example, the concept of pure things.
3. The difference between pure substances and mixtures
Activity and Exploration: How to "capture" the air in one container into another container?
Two. Nitrogen and rare gases
Read P28-29 and answer according to the collected data:
(1) What are the uses of nitrogen?
(2) Why are rare gases also called "inert gases" and what are their important uses?
What kind of gas does rare gas mean?
3. Humans need clean air.
Teacher's explanation
Display icon
Discussion: (1) What are the air pollution sources?
(2) How to prevent air pollution?
(3) What are the pollutants in the air?
Summary:
Homework: 1. P3 1 Practice and practice
2. How to collect a bottle of air sample from the warehouse?
Active oxygen in the second quarter
Li Chungang Zhenjiang experimental school
First, the teaching objectives:
1. Cognition: 1. Understand the important physical and chemical properties of oxygen and summarize the chemical properties of oxygen.
2. Understand the use of oxygen and the close relationship between oxygen and human beings.
3. Understand the industrial preparation method of oxygen, and learn the principle, device and operation of preparing oxygen in the laboratory.
2. Ability: cultivate students' experimental operation ability, observation ability and thinking ability.
3. Emotion: Develop meticulous observation habits and rigorous work style when exploring material properties.
2. Teaching focus: 1. Master the chemical properties of oxygen
2. Principle, device and operation of oxygen production in the laboratory.
Teaching methods: experimental exploration, communication, comparison and induction.
Four. Teaching preparation:
Charcoal, fine iron wire, candle, potassium permanganate, hydrogen peroxide, manganese dioxide, matches, alcohol lamp, iron frame (iron clip), gas container, burning spoon, water tank, conduit (rubber tube), separating funnel, medicine spoon (paper slot) and cotton ball.
Verb (abbreviation of verb) teaching schedule: 2 hours.
Teaching process of intransitive verbs;
First teaching time
[Introduction] Oxygen is one of the main components of air. All living things on the earth are inseparable from oxygen. Human production activities also need oxygen.
What are the important properties of oxygen?
[Preview homework communication]
1. Example: Many examples in life illustrate the nature of oxygen.
2. There is oxygen dissolved in water in nature. Can you do an experiment or give an example from life to illustrate it?
Do you know the function of oxygen? Please give an example.
[blackboard writing] 1. Understand the nature of oxygen
[Students reading] P33
[Image display] Figure 2-7 and Figure 2-8
[Students exchange and discuss]
Physical properties of oxygen
[Teacher's Summary] When external conditions change, all substances can be transformed into each other in three forms (solid, liquid and gas).
[Activities and Inquiries]
1. Charcoal burns in air and charcoal burns in oxygen.
2. Fine iron wire burns in air, and fine iron wire burns in oxygen.
3. Candles burn in air and candles burn in oxygen.
[Recording phenomenon]
The literal meaning of oxygen in the air
1
2
three
[Discussion and communication]
1. What is the difference between the reaction of substances in the air and oxygen?
2. What do you know about the nature of oxygen through the above experiments?
[Analysis] Combustible substances usually burn more violently in oxygen than in air.
Some substances that are not easy to burn in air can burn in oxygen.
[Students reading] P35
[Summary] Oxygen is a chemically active gas.
[communication and discussion]
According to the nature of oxygen, it is assumed that oxygen is used.
Give examples to illustrate the influence of oxygen on people's daily life.
Second teaching time
[knowledge preparation]
1. The proportion of each component in the air is relatively stable. What is this?
2. The reaction between substances and oxygen, some more intense, such as _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _; Some of them are slower, such as _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.
Do you know how to make oxygen?
[Blackboard] Two. The use of oxygen
[Image display] Figure 2- 12
[Discussion] The use of oxygen
[Question] What is the relationship between the use and nature of oxygen?
[Blackboard] Three. Contact with oxygen
[Explanation] Oxygen supply method for industrial vegetation
[Activities and Inquiry] (completed under the guidance of teachers)
Experiment 1. Heating potassium permanganate
Points for attention of students in reading P37
[Grouping experiment] 1. Potassium permanganate: _ _ _ _ _ _ color _ _ _ _ _ state.
2. Experimental phenomena
3. Write a written expression (teacher's guidance)
[Exchange and discussion] 1. What are the properties of potassium permanganate obtained in the experiment?
2. How to test the gas produced by the reaction?
3. What are the basic operations involved in the experiment?
4. What should we pay attention to in the experiment?
Experiment 2. Decomposition of hydrogen peroxide (hydrogen peroxide)
[Group experiment] 1. Hydrogen peroxide has a color of _ _ _ _ _ _ _ _ _.
Manganese dioxide _ _ _ _ _ color _ _ _ _ state
2. Record the experimental phenomena
3. Write a written expression (teacher's guidance)
[Exchange and discussion] 1. What are the properties of hydrogen peroxide obtained in the experiment?
2. How to test the gas reflecting the output?
3. What are the basic operations involved in the experiment?
[Teacher explains] The industrial manufacturing method and principle of oxygen; Laboratory preparation method, principle and operation points of oxygen.
[Extracurricular activities] Looking for information, what other ways to make oxygen?
[homework] P38 5
The third quarter wonderful carbon dioxide
Yeung Yi Zhenjiang experimental school
First, the teaching objectives
Knowledge requirements: 1. Understand the main physical properties of carbon dioxide and master its chemical properties.
I can only understand the method of making carbon dioxide and the method of collecting gas.
3. Understand two basic reaction types: combination reaction and decomposition reaction.
4. Understand the arrival effect and El Ni? o phenomenon, and understand the role of carbon dioxide in the natural cycle and its significance to human life and production.
Ability requirements: learn to observe and describe the experimental phenomenon of carbon dioxide and summarize some properties of carbon dioxide.
Emotional attitude: make students have a deeper understanding of human life from the perspective of chemistry, gradually learn to care about life, solve problems in life, and further establish the concept of environmental protection and sustainable development.
2. Teaching emphases and difficulties
Explore and master the chemical properties of carbon dioxide.
Laboratory preparation method and gas collection method of carbon dioxide.
Three. teaching method
Experimental inquiry, observation and comparison, reading and discussion, induction and summary.
Four. Knowledge preparation
Collect information about the cycle and use of carbon dioxide from textbooks and other books or online, and then exchange and discuss it in class.
Verb (abbreviation for verb) Course schedule: 2 hours.
Teaching process of intransitive verbs
The first lesson: the nature and use of carbon dioxide
[Introduction] Recall the composition and volume fraction of air.
【 Question 】 Through learning, we know that nitrogen, oxygen and rare gases, which account for most of the air volume, are of great significance and use to human beings. So carbon dioxide, which accounts for only 0.03% of the air volume, is insignificant to us? Can we live without it in the atmosphere? How about some more?
[Students] Think and answer.
【 Conclusion 】 Nature needs some cycles to maintain a certain concentration of carbon dioxide in the atmosphere.
[Student] 1. Discuss and fill in Table 2-4 of P39 "Generation and Consumption of Carbon Dioxide in the Atmosphere".
2. Think and communicate the causes and effects of the greenhouse effect.
3. Read P40 Table 2-5 and "Broaden your horizons".
[Transition] Apart from having an important impact on the environment, carbon dioxide is also widely used in our life and production (for example). This first requires us to understand its changes and nature.
[Experiment] 1. Look at the color and state of carbon dioxide and smell it.
2. Dissolution of carbon dioxide in water
Experimental Steps: "Observation and Thinking" of P39
[Student] 1. Observe and describe the experimental phenomena (fill in the study plan).
2. Read P4 1-42 and discuss the physical properties of carbon dioxide.
[Summary] Physical properties of carbon dioxide:
1. Colorless and almost tasteless gas;
2. The density is higher than air;
3. Soluble in water, with three-state changes.
[Experiment] 1. Reaction of carbon dioxide with water
Experimental Steps: Book P39 "Activities and Inquiry"
2. Carbon dioxide fire extinguishing experiment
Experimental Steps: Book P4 1 "Activities and Inquiry"
[Student] 1. Observe and describe the experimental phenomena (fill in the study plan).
2. Read the textbook to understand the concepts of combination reaction and decomposition reaction.
[Summary] Chemical properties of carbon dioxide:
1. generally does not support combustion and cannot help breathing;
2. It can react with water to generate carbonic acid, which is unstable and easy to decompose;
3. It can react with limewater to produce calcium carbonate.
[Student] According to the physical properties, chemical properties and collected materials of carbon dioxide, the main uses of carbon dioxide are summarized through exchanges and discussions.
【 Summary 】 Uses of carbon dioxide:
1. dry ice as refrigerant;
2. Used for general fire fighting;
3. Fertilizer for photosynthesis;
4. Make soda, etc.
【 Summary 】 Grasp the physical and chemical properties of carbon dioxide, and understand its circulation and use.
[Homework] Book P45-46 1, 3
The second class: laboratory preparation of carbon dioxide and its influence on health
[Introduction] Review the physical and chemical properties of carbon dioxide
Communicate and discuss the reactions that produce carbon dioxide.
[Analysis] Laboratory carbon dioxide production needs to meet the requirements of simple conditions, convenient and safe operation and pure products.
[Experiment] Book P4 1 Activity and Inquiry Experiment ○ 1
[Student] 1. Observe and describe the experimental phenomena (fill in the study plan).
2. Read P43-44 and discuss the laboratory preparation and gas collection methods of carbon dioxide.
[Summary] Laboratory preparation of carbon dioxide;
medicines and chemical reagents
2. Principles
3. Generation and collection device
4. Collection methods and principles
5. Comprehensive inspection method
[Students] Read P44-45 to understand the impact of carbon dioxide on human health.
[Discussion] 1. In the story "Dead Dog Cave", why does the dog faint after entering the cave, but people are fine?
2. Before entering a food cellar that has not been opened for a long time, how can people check whether the carbon dioxide content in the food cellar will pose a threat to the lives of people entering the food cellar?
3. When studying in the classroom, why should we keep the classroom ventilated?
【 Summary 】 Focus on the laboratory preparation methods and gas collection methods of carbon dioxide.
[Homework] Volume 46 Pages 4, 5 and 6
Attachment: student study plan
1. Observe the color and smell of carbon dioxide.
Experimental phenomena: color _ _ _ _ _ _, state _ _ _ _ _, smell _ _ _
Experimental conclusion: carbon dioxide is _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.
2. Dissolution of carbon dioxide in water
Experimental Steps: "Observation and Thinking" of P39
Experimental phenomenon: there is _ _ _ _ _ _ _ in the soda bottle, and the lime water becomes _ _ _ _.
Experimental conclusion: Carbon dioxide _ _ _ _ is soluble in water, and more _ _ _ _ _ will be produced with the increase of pressure. Carbon dioxide can turn clarified limewater into _ _ _ _ _ _, which is also a method to identify carbon dioxide gas.
Experimental thinking: What method can make more carbon dioxide come out of soda water?
3. Carbon dioxide reacts with water
Experimental Steps: Book P39 "Activities and Inquiry"
Experimental phenomenon: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
Experimental conclusion: carbon dioxide can react with water to generate _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ gas.
Experimental thinking: how to check the air tightness of devices?
What are the precautions when heating tube A?
4. Carbon dioxide fire extinguishing experiment
Experimental Steps: Schedule P4 1 "Activity and Inquiry" Experiment 02.
Experimental phenomenon: the candle in _ _ _ _ in ○2 goes out first.
Experimental conclusion: carbon dioxide cannot _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.
5. Laboratory preparation of carbon dioxide
Experimental steps: schedule P4 1 "activity and inquiry" experiment ○ 1
Experimental phenomenon: ○1_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.
Experimental conclusion: _ _ _ _ _ _ _ _ and _ _ _ _ _ reactions can be used to prepare carbon dioxide in the laboratory, which can be collected by _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.
Experimental thinking: What are the advantages of dropping dilute hydrochloric acid with a separatory funnel?
Why not use drainage at ordinary times, but use upward air to collect carbon dioxide?
How to check that carbon dioxide has been collected in the container? How to prove that carbon dioxide has been collected?
Section 4 Water in Nature
Zhang Meihua Zhenjiang experimental school
First, the teaching objectives
learning target
1, know the composition of water;
2. Understand the difference between natural water, natural water, applied water, mineral water and distilled water;
3. Understand the close relationship between water and human beings. Water is a valuable resource for human beings.
4. Understand the factors of water pollution and the basic methods of water purification;
5. Know the purpose of filtering; Learn the basic device and operation method of filtration.
6. The composition of water can be analyzed from the decomposition and synthesis of water.
7. Establish the concept that water is a valuable resource, save water and consciously protect water resources from pollution.
Process and method: The composition of water can be analyzed from the decomposition and synthesis of water.
Emotions, attitudes and values:
Understand and appreciate the close relationship between water and human beings, understand the seriousness of water shortage and water pollution, cultivate environmental awareness and establish a sense of social responsibility.
Second, the key points and difficulties
Teaching focus:
(1) Understand the composition of water (2) Source, harm, prevention and purification of water pollution.
Teaching difficulties:
Understanding the composition of water from the perspective of elements
Third, the method of teaching and learning: guided inquiry method; Experimental inquiry, observation and comparison, reading and discussion, induction and summary.
Fourth, class hours 2 class hours
5. Prepare a hydrogen balloon, a bottle of river water, a bottle of well water, tap water, distilled water, a small amount of washing powder, a water electrolyzer, other instruments and experimental CDs.
Six, knowledge preparation
1. Write down where water exists in nature according to your knowledge of water. What are the main physical properties of water?
Do you know what kind of reaction is a combination reaction? What kind of reaction belongs to decomposition reaction? Give an example of each.
3. How do you understand mixing and purity? Please give an example.
4, access to information about water, water use, water pollution and other related information, you can query from the library or education website, and communicate with students after finishing.
Seven. Teaching design
[Communication] What do you already know? P47
We know that water is both common and precious. So, what is water made of?
What is water made of?
[Observation and Thinking] Experiment 1: Observe the electrolysis experiment of water.
(1) What happens to the two electrodes when the DC power supply is turned on? Stop power supply, the phenomenon in two glass tubes?
(2) How to check the gas in two glass tubes? What phenomenon was observed during the inspection?
Experiment 2: ignite pure hydrogen in the air, cover a dry cold beaker above the flame, and observe the experimental phenomenon.
[Summary] Power on
Water, hydrogen and oxygen
Hydrogen+oxygen ignites water
[Communication and Discussion] (1) How much do you know about the composition of water?
(2) What is the difference between the boiling process of water and the decomposition process of water?
(3) Some people say that water can be developed into energy. what do you think?
(4) What are the similarities and differences between natural water, mineral water, tap water and seawater?
[Summary]: Composition of water.
Question scenario: How to distinguish pure water, water containing soluble solid impurities and water containing small solid particles? How to remove insoluble solid impurities from water?
Second, the purification of water.
[Activities and Inquiry1] P49 What's the difference between water with the same appearance?
[Discussion and communication] (What do you see when evaporating? What is the conclusion? What may happen when it evaporates? What should I pay attention to? )
[Explanation] Water is pure, but there is almost no pure water in nature. The natural water used in our daily life contains some impurities and bacteria more or less, which is not suitable for direct application. All kinds of industrial water also have different requirements for water quality. Therefore, it is necessary to purify water.
[Activity and Exploration 2] P49 Objective To explore the difference between hard water and pure water.
[Discussion and communication] (group communication report)
[Reading] P49 Last paragraph
[Summary] The difference between hard water and pure water
【 Activity and Exploration 1, 2 】 Objective To understand the simple method of removing small particles from water through experiments. You can watch CDs.
【 Summary 】 The function of alum and the applicable scope of filtration.
[broaden your horizons] watch the CD to understand how tap water is produced. Let students know to save water.
Third, the use of water.
[Exchange and discussion] (1) The importance of water to people's future life and industrial and agricultural production.
(2) Understand the world water resources. Determine which day of the year is World Water Day.
(3) Collect the water pollution around you.
(4) In view of the problems existing in water use, people put forward some suggestions on saving water.
(5) The meaning of water-saving emblem.
Narrator: Every citizen should establish the consciousness of protecting water resources and form the good habit of saving water.
[Summary of this lesson] Student summary
[Assignment] P52-53 4, 5, 6; Collect topics about water that you are interested in.
[Feeling after teaching]
class exercise
[Observation and Thinking]
1. Electrolyzed water (textbook 48 pages)
Experimental phenomenon: both electrodes are exposed. The gas energy produced by the negative electrode and the gas produced by the positive electrode can make the wood strip take to Mars. The volume of gas produced by the negative electrode is twice that produced by the positive electrode.
Thinking: Experimental conclusion: water ()+. Water consists of water and water. Given that the density of hydrogen is 0.0899 g/L and the density of oxygen is 1.429 g/L, the mass ratio of hydrogen to oxygen in water is:
2. Hydrogen combustion experiment (textbook page 48)
Experimental phenomena:
Experimental conclusion: hydrogen is sexual, and hydrogen+ignition.
3. If the hydrogen in the hydrogen balloon is pure, design an experiment to export the hydrogen and let it burn quietly.
Pure water is a colorless, odorless and tasteless liquid. The density at c is 1g/cm? ; Water is decomposed into hydrogen and oxygen after being electrified; 10 1kPa, the freezing point of water is 0? C, the boiling point is 100? c； Water vapor can be mixed with hot coal to produce water gas. According to the above description, what are the physical properties of water? What are the chemical properties of water?
5. Comparison of tap water, river water and well water.
Experimental steps: (1) Observe color, fragrance and taste; (2) slight heating observation phenomenon; (3) Add 1 teaspoon of washing powder respectively, mix them evenly, then put them into a handkerchief for rubbing and observe the foam.
Experimental conclusion: Tap water. Well water. River water.
[experimental inquiry]
"Activities and Inquiry" on pages 49 and 50 of the textbook.
1. Evaporation is a process in which solvents are constantly volatilized. Put the liquid into the pot, then put it on the table of the iron frame and heat it with alcohol lamp. In the process of heating, constantly stir with a glass rod to prevent. When a large number of solids appear in the evaporator, the evaporator stops working. Just in case.
2. Filtration: Filtration is a method to remove mixed liquid. When making a filter, the edge of the filter paper should be the edge of the funnel, the liquid level should be the edge of the filter paper, and the filter paper should be the inner wall of the funnel. When filtering, the beaker notch should be close to the filter paper layer of the glass rod. The function of the glass rod is. After filtration, the filter paper is left. The filtrate is a shape.
[Discussion and communication]
The purpose of the activity: to understand the extensive use of water in industrial and agricultural production and life, to improve the understanding that water is a precious natural wealth of human beings, and to generate feelings of protecting and saving water resources.
Activity process: collect information about water use from textbooks, books, online or around production and life, summarize and sort it out, exchange and discuss it in class, and finally summarize the main uses of water.
1. Among China's four great inventions, the use of water is the most closely related to chemistry, and the industrial production related to the above is mainly caused by water pollution in the Huaihe River Basin. Products that are prone to air pollution may also cause personal injury.
2. Faced with the serious pollution of the lake, it was suggested that: ○ 1 sewage sluice should be set to treat the sewage entering the sluice in advance. ○2 Lead the Yangtze River water to flush the toilet and make the stagnant water come alive. ○3 Restore the planting of lotus root, water chestnut and water hyacinth in the lake, and use the water purification function of plants to recycle the leaves and stems of plants. Please comment on the above three suggestions. According to what I have learned, I put forward a comprehensive treatment plan for lake water pollution.
3. What methods can be used to identify the following groups of substances?
(1) water and alcohol (2) hydrogen and carbon dioxide (3) water and salt water.
(4) Hard water and distilled water (5) Water and dilute hydrochloric acid
4. After a student filtered the muddy water, he found that the filtrate was still turbid. Would you please analyze the reasons for the turbidity of the filtrate? How are you going to repair it?
5. There is a cup of seawater mixed with sediments, and salt solids need to be removed. Please write down the main steps of the experiment and what problems should be paid attention to in the experiment.