Tisch
[Background] Observation is the beginning of scientific inquiry and primary school students' understanding of the world. If teachers can take corresponding strategies from students' existing experience and age characteristics, so that students can experience the fun of observation and feel the method of observation in the process of "trying, discovering, correcting, trying and rediscovering", then students will be happy to observe, diligent in observing and good at observing, and students can also obtain a lot of perceptual materials through observation, laying a good foundation for the next scientific inquiry.
After learning about "surrounding plants" and "various parts of plants", Mr. Zhang hopes that students can explore the diversity of plant leaves by themselves through many observations.
[process]
Teacher Zhang pointed to the trunk of a willow tree drawn on the blackboard and asked: Who can add leaves to the willow tree? Three students draw leaves on the blackboard. After the students finished painting,
Teacher: Why did you choose yellow chalk?
Health: Because autumn has come, the leaves of willow trees have turned yellow.
Teacher: Why do you choose green?
Health: Because spring has come, the willows are green.
Teacher: Why did you choose blue?
Health: Because the sky is blue.
Teacher Zhang faces the class: What color leaves have you seen?
Health: I see dark green, too.
Health: I've seen orange ones, too.
Teacher: Teacher Zhang has also prepared some plants for you. Please find out if there is any color you just mentioned. Are there any other colors? Each child is responsible for recording the colors of six kinds of leaves.
Students observe and record the colors of plant leaves.
After a while, Mr. Zhang showed the records and organized students to communicate.
Then ask the students to classify the photos of plant leaves according to their colors. In this process, students found that: the colors of plant leaves are varied; Even if there are yellow and green leaves, the position is different; There are the most green leaves.
Teacher Zhang pointed to the yellow leaves and green leaves recorded by the students and said, Guess how many leaves she recorded?
Health: No.5 leaf.
Health: No.8.
Health: No.5.
Health: No.8.
Teacher: Is there any way for everyone to guess which leaf you remember? Let's discuss it.
Students discuss in groups and record the leaves of plants again. After a while, Mr. Zhang organized the students to play guessing the leaves.
Teacher: Who wants to guess what they drew?
What leaves did he draw?
Health: No.5 leaf.
Teacher: Is she right?
Health: Yes.
Teacher: On what basis did you guess?
Health: Guess by color, green and yellow.
Teacher: How do you draw it?
Health: Color it green first, and then add yellow dots.
Teacher Zhang invited another student: Which leaf is this?
Health: It's the No.1 leaf, octagonal gold plate.
Teacher: Is she right?
Health: Yes.
Teacher: How do you draw it?
Health: First, count how many angles a leaf has, nine angles, and then draw it.
Teacher Zhang invited another student. Everyone was very enthusiastic, so she organized her classmates to have a "leaf guessing game" in the group. After that, Teacher Zhang leads the students to summarize.
Teacher: Do you have any good ways for others to guess?
Health: Draw clearly.
Health: Draw its shape.
Health: The color should be the same as the painting.
Teacher (supplement): You can draw wherever you want.
Health: Draw the outside first, then the inside.
Teacher: By drawing leaves, we know that leaves are different except for their colors.
Health: appearance.
Health: size.
Health: the pattern.
Teacher: What are the leaves like?
Health: All kinds.
Teacher: We call them all kinds of leaves. The teacher provided 12 plants for everyone today. Do you know how many kinds of plants exist in nature?
Students observe all kinds of leaves (multimedia).
Teacher: Think about it. Is there a difference between Ye and what I just said? What else can be observed?
Health: You can also smell the leaves of edible plants with your nose, touch them with your hands and taste them with your tongue.
Teacher: Are the leaves of willows in nature like those you painted? (The teacher points to the leaves that the students drew on the blackboard for the first time)
Health: No.
Teacher: Please add more leaves to the willows when they sprout in spring.
[thinking]
How to cultivate junior high school students' interest, ability and habit of observation?
[analysis and thinking]
First, cleverly set the situation to stimulate students' interest in observation
In this case, Teacher Zhang asked the students to draw leaves three times.
The first time: individual students went to the blackboard to "add leaves to the willow". Teacher Zhang used wicker and colored chalk to stimulate students' interest in drawing leaves on the blackboard. Second time: Each student "seeks to record the colors of other leaves". Teacher Zhang said, "Do you have the color you just mentioned? Are there any other colors?" Stimulate students' interest in drawing leaves. The third time: each student "draws a leaf that others can guess at a glance". Teacher Zhang used students' competitive psychology to push students' interest in observation to a climax again.
First-year students have short attention span, and have no interest and enough patience to observe the same thing repeatedly. Using students' curiosity and competitive spirit, Mr. Zhang skillfully used the strategy of drawing leaves three times to create situations, which made students unconsciously accept and complete tasks again and again, and their interest in observation increased again and again.
Second, create conflicts and cultivate students' observation ability
After students painted leaves for the first time, Teacher Zhang used the differences between students and the contradiction between students' existing experience and unknown knowledge to ask students to find and record "Is there any color you just mentioned? Will there be other colors?" Let the students observe purposefully with questions.
After the students painted the leaves for the second time, Teacher Zhang pointed out that the students only painted yellow and green, and there was no color distribution, so that everyone could "guess which leaf he painted". Create conflicts again, cause arguments, and guide students to find problems in conflicts: how to record them so that others can guess which leaf was painted at a glance? So cultivate students' observation methods.
After the students smoked leaves for the third time, Teacher Zhang asked the students to play the game of guessing leaves again. On the basis of students' successful experience, let students talk about "how did you guess" and "how did you draw", and guide students to sum up successful experiences.
In the activity of three-leaf painting, which requires gradual improvement, students' observation is more and more comprehensive and detailed, and their observation ability is gradually improved. In the reflection after guessing the leaves twice, the students themselves realized the method of observing the leaves, and the observation habit was also cultivated. As a result, they found that there are more and more differences in plant leaves, from the initial color, shape and size to the later edges, leaves and veins. Finally, from eye observation to sensory observation with nose and hands.
In short, clever situational settings can stimulate students' interest in observation. Creating conflicts is conducive to cultivating students' observation ability. Teachers should be good at starting from students' existing experience and age characteristics and adopt corresponding strategies, so that students can gradually gain experience and understanding of knowledge, methods and attitudes through repeated and in-depth observation.
extreme
Teaching objective: 1. Scientific inquiry: experience the process of lighting a small light bulb with one or two wires and a dry battery, explore the law of lighting a small light bulb, gradually observe scientific things purposefully and carefully, and learn certain methods.
2. Emotional attitude and values: cultivate students' interest in exploring how to light small light bulbs and learn to cooperate and communicate with others.
3. Scientific knowledge: knowing that only the current passes through the small light bulb will emit light, can draw a simple circuit, and can find out the reason why the small light bulb does not light up.
Teaching emphases and difficulties:
1. Observe scientific things purposefully and carefully, and explore the law of lighting small light bulbs.
2. Know that only current will shine through the small light bulb, and find out the reason why the small light bulb is not bright.
Teaching preparation:
Group: a battery, a small light bulb and two wires.
Demonstration: composite pictures of small light bulbs, pictures of small light bulbs and batteries, multimedia.
Teaching process:
(1) import
Dialogue: I have a small toy. do you want to see it ? Show me the toy flashlight and have a look again. Why is it open? (There are small light bulbs, batteries ...) Looking inside, there are indeed small light bulbs.
(2) New curriculum
Observe and understand the structure of small bulbs.
1. Dialogue: I have a small light bulb here. Can you light it? No, you need batteries and wires. ) why? There is electricity in the battery, and wires can get electricity from the positive and negative poles of the battery. ) Give you a battery and some wires. Can you light the light bulb? Give it a try!
2. Students try to light small light bulbs.
3. Communication: Tell me how you connect.
4. Inspiration: Why should a small light bulb be connected with a battery and several wires? Some groups light small light bulbs, while others don't? Why can't students who light bulbs tell the truth? Did we miss anything? For example, carefully observe the structure of a small light bulb. Sometimes, in-depth and meticulous observation is the basis of successful experiments.
5. Group observation: What does a small light bulb look like? (showing pictures)
6. Student statement, teacher's summary, blackboard writing: The shell made of glass on the small bulb is called glass bulb, the metal wire inside the glass bulb is called filament, the metal wire is below the glass bulb, and the black spot at the bottom is called solder joint.
7. Tell us: What will you find if we peel off the metal wire (uncover the composite page of the wall chart)?
8. Students stated after observation: one end of the filament is connected to the metal wire, and the other end is connected to the bottom solder joint. In this way, when the current passes through the filament, the small bulb will emit light.
9. Projection: dissect the small light bulb (see the figure below)
10. Question: Knowing the structure of the small light bulb, what do you want to do most? Now, let's light our little light bulbs together!
(Title: Light our little light bulb)
Explore the law of lighting small bulbs
1. Requirements: Group experiment. Two students have a set of materials. Draw as many connection methods as possible on the paper. Draw the lighting mode on one side and the lighting mode on the other. The students who finished first showed the method on the blackboard with pictures and chalk. Please look carefully, and the same method already shown on the blackboard will not be posted.
2. Students operate and teachers patrol and guide.
3. Discussion: Let's see how many ways (numbers) there are to light a small light bulb, and whether they can all light a small light bulb. (Cover up the controversial ones first) Everyone agrees that the rest of the picture should be bright. Let's take a closer look. Do their connection methods have anything in common?
4. Student communication, teacher's summary, multimedia blackboard writing: the metal wire of the small light bulb and the solder joint at the bottom should be connected to the two poles of the battery respectively.
5. Judgment: Let's take a look at these controversial pictures. Can we be sure if they are bright now? (student exchange).
6. Let's take a look at the connection diagram of these small light bulbs. Can you find out why they don't light up?
7. student exchange. (Emphasize the formation and harm of short circuit, and demonstrate it, so that students can feel that the wire is hot, and at the same time carry out safety education. )
(3) Extended activities:
How many batteries are there in it? (two batteries). How can a small light bulb connect two batteries? (Merging teams and exploring together)
Teaching record
Teacher: I have a small toy. Do you want to see it? (Showing the toy flashlight), have a look again. (Open) Why is it open?
Health: There is a small light bulb in it.
Health: There are batteries in it.
Open the bright flower-shaped shell and look inside. There are indeed small light bulbs. )
Teacher: I have a small light bulb here. Can you light it?
Health: Yes.
Health: No, you need batteries and wires.
Teacher: Why?
Health: The battery has electricity.
Health: Wires can draw the electricity out of the battery.
Health; I know there are positive and negative batteries. Stick a picture on the board and mark the positive and negative poles.
Teacher: Now I'll give you a battery and some wires. Can you light the light bulb? Give it a try!
Students try to light small light bulbs confidently in pairs. Some groups are bright, and some groups are not. Teachers patrol the group experiment, please show the connection method on the blackboard for the bright group and the unlit group respectively. )
Teacher: (pointing to the picture) Tell me about the group that didn't light the small light bulb. How did you connect it?
Health: I thought the electricity in the battery could be wired to the light bulb, but the light bulb didn't work.
Teacher: (pointing to the picture) Tell me the group that lights the small light bulb. How do you relate them?
Health: I put the battery and light bulb in a circle with wires, and it only lights up.
Teacher: Why are you doing this?
Health: (silent for a moment) I don't know.
Teacher: Do other students know?
Health: (Silence).
Teacher's inspiration: everyone uses a battery and several wires to connect small light bulbs. Why do some groups light small light bulbs while others don't? Why can't students who light bulbs tell the truth? Did we miss anything? For example, carefully observe the structure of small light bulbs before operation.
Students have experienced setbacks and failures, but they have aroused the desire to explore and listened carefully and quietly. )
Teacher: Sometimes, careful observation is often the key to the success of the experiment. Let's calm down and have a good look at the small light bulb from the outside to the inside to see who can observe it carefully and make it clear.
Students observe in groups: What is a small light bulb like? )
The teacher posted a composite picture of a small light bulb on the blackboard and asked the students to describe it.
Health: The light bulb has a spherical shell made of glass, which can protect the filament inside. Its lower part is a layer of skin surrounded by yellow metal, with circles of stripes on it.
Health: the filament of a small bulb is wound in a spiral shape, which is different from the material used in the metal brackets at both ends.
Health: there is a gray spot at the bottom of the small light bulb, and there is a circle of gray glass around it.
……
Health: There is a blue glass between the two metal brackets of the small light bulb. Teacher, I want to ask, what is that blue glass for?
Teacher: (smiling approvingly) I appreciate your quality of daring to ask questions. That small blue glass can fix and separate two metal brackets, so that the filament can shine better.
Health: (smiles and nods)
Teacher: (while summarizing the blackboard book) The glass shell on the small bulb is called a glass bulb, the metal wire inside the glass bulb is called a filament, the metal wire is below the glass bulb, and the small black dot at the bottom is called a solder joint.
Teacher: Where are the two metal brackets supporting the filament connected? It is covered by a metal threaded shell. According to the light bulb on the blackboard, guess where the metal bracket is connected.
Health: One end of the filament may be connected to the metal wire, and the other end should be connected to the solder joint at the bottom.
Teacher: Do you agree? (projection anatomy of small light bulbs. Sure enough, the students cheered. In this way, when the current passes through the filament, the small bulb will emit light.
Teacher: Knowing the structure of the light bulb, what do you want to do most? Now, let's light our little light bulbs together!
(Title: Light our little light bulb)
Teacher: Two students cooperate. The students who finished first showed the method on the blackboard with pictures and chalk. Please look carefully, and the same method already shown on the blackboard will not be posted.
The students tried to light the small light bulb again, and cheers came and went in class. Nine connection modes are quickly displayed on the blackboard. )
Teacher: Let's see how many ways (numbers) there are to light a small light bulb. Can they all light a small light bulb? (Cover up the controversial ones first) Everyone agrees that the rest of the picture should be bright. Let's take a closer look. Do their connection methods have anything in common?
Health: To make the light bulb light up, it is necessary to connect the battery anode with solder joints and the battery cathode with metal wires. Or connect the positive electrode of the battery with a metal wire and the negative electrode with a solder joint.
Teacher: (while summing up, multimedia blackboard writing) The metal wire and solder joint at the bottom of the small bulb should be connected to the anode and cathode of the battery respectively.
Teacher: Let's take a look at this controversial picture. Are you sure it's on now?
Student's judgment: the light bulb should be lit like this. Because the solder joint of the small light bulb is connected to the positive electrode of the battery, his metal wire is connected to the negative electrode of the battery with two wires, and the small light bulb is still bright, but he uses two wires, which is a bit of a waste of resources.
Teacher: Let's look at the connection diagram of these small light bulbs. Can you tell us why they are not on?
Health: the first method is that the solder joint of the small bulb is not connected to the negative electrode of the battery.
Health: The second method is that the negative electrode of the battery is connected to the positive electrode of the battery instead of the metal wire of the small bulb.
Health: The anode and cathode of the battery are connected to the metal wire of the small bulb, and the solder joints are not connected.
Teacher: The students observed carefully, especially reminding everyone of the second method. The negative electrode of the battery is directly connected to the positive electrode of the battery. This wrong connection is called short circuit. Short circuit will quickly consume the electricity in the battery, make the wires hot, and even cause a fire. (Demonstration: Connect the bare wires directly to the positive and negative poles of the battery, so that students can feel that the wires are hot and carry out safety education at the same time. )
Teacher (showing the beautiful toy flashlight again): How many batteries are there in it? (Take out: two batteries). How can a small light bulb connect two batteries?
The students formed a group to explore together, and excited cheers came from time to time in the classroom, which pushed the learning atmosphere to a climax. )
Tisso
First, introduce the teacher: Today, the teacher gave you a class for the first time and brought you a special gift. Do you like it?
Health: Yes.
Teacher: To get these gifts, everyone needs to complete a small task and take out a blank piece of paper. Today, let's observe the characteristics of paper. Writing on the blackboard: "Observation on paper"
[Comment: This introduction is intuitive in image, clear in task, straight to the point, saving time and mobilizing students' interest in inquiry with tasks. ]
Secondly, observe a blank sheet of paper.
1. Estimate.
Teacher: Let's estimate how many features you can find if you get this blank piece of paper.
Health: Only 1 can be found.
Teacher: What about the other students?
Health: I can find three.
Teacher: Anything else?
(5, 7, 10)
Teacher: He said he could find 10 features. Can you believe it?
Health (together): I don't believe it.
Teacher: But the teacher believes it. He can find 10 features. (The classroom suddenly fell silent)
[Comment: Through the estimation of this activity, a challenging activity scene was created. It is difficult for junior three students to observe the characteristics of 10 on a blank sheet of paper. They haven't tried it, and they don't believe it reflects students' honest character, so they have doubts and motivation to try. ]
discuss
Teacher: Try to find the 10 feature after you get the blank paper. How are you going to observe it? What method is used to observe?
Health: Touch with your hands, smell with your nose, observe with your eyes, and use a magnifying glass. ...
Teacher: You have so many methods!
Observe.
Teacher: Later, we will compare which group can find the features of 10 or above in white paper, and record the observed features simply and quickly. We play music in the name of music. After the music stops, we add a small five-star to the group that can observe the characteristics of 10. The team leader took out the covered white paper. Get ready/start. (Students observe a blank sheet of paper in the way just discussed, discuss and record with each other ... After the music stops, the group leader collects materials, and the two groups raise their hands to show that they have found the 10 feature, and the teacher gives them five-star encouragement. )
[Comment: Find out the 10 feature of a piece of white paper through the task in the observation activity, and urge students to think and participate in the activity-in order to observe the 10 feature, what methods can we use to observe it?
Before organizing the exchange activities, let the group leader put the materials away and cover them on the plate, which can effectively control the materials and let the students leave the materials temporarily. So that students' attention can be effectively transferred to communicative activities. ]
4. communication.
Teacher: Ask a group of representatives to report on the stage and make records.
Health: This white paper is quadrangular, white, very thin, especially soft, very fragrant and transparent, and it is very wrinkled and light after sliding and folding.
Teacher: What time is it? (Ask the students who are listening)
Health: 9 o'clock.
Health: it is uneven after folding.
Teacher: Do other groups have anything to add?
Health: There are many small holes with a magnifying glass.
Health: There are shadows.
Teacher: How many points have we found so far?
Student: 12 o'clock (many students raised their hands to talk about the characteristics of the white paper)
Teacher: I didn't expect an ordinary piece of white paper to have so many characteristics. It seems that as long as you try to observe, you can find more secrets of paper.
[Comment: In students' communication activities, it shows that as long as you try to observe with your senses, you can find the characteristics of white paper above 10. The white paper's very transparent observation in communication is contradictory to the shadow of the white paper. Reflect that students' expression of transparency is not clear, and teachers can put forward guidance in time, such as asking him: How did you find transparency? What words are appropriate to record your observations? ]
Three, the observation of two pieces of paper
1.
Teacher: We have all kinds of paper in our life. Show me a piece of brown paper. If I send it to you, there will be two kinds of paper. What do you want to observe when you get two kinds of paper?
Health: Compare these two kinds of paper?
Teacher: What do you compare them with?
Health: It's a little different.
Teacher: Do you want to compare different characteristics?
Student: Yes.
Teacher: Let's see which group can compare these two kinds of paper with more different characteristics.
[Comment: The teachers here use the suggestive function of the materials to subtly narrow the scope of the research questions and pass them on to students, so that students can ask questions after making feasibility judgments according to these conditions. Teachers fully respect students' right to choose independently, so that students can find the problems and research methods they want to study next in a short time. Teachers follow students' ideas and guide students to compare two pieces of paper, which fully embodies the role orientation of teachers as "the best among equals". ]
2. Observe:
Teacher: The team leader takes out the kraft paper in the drawer and prepares/observes (music: each student has a piece of kraft paper to observe by smelling, touching and reading, and the teacher issues a record sheet, and each group has a recorder to take notes).
3. communication:
(The teacher asked a group of representatives to take the record form and put it on the physical booth to report. )
Health: White paper is smaller than kraft paper. White paper is slippery, kraft paper is slippery, and one side is rough. White paper is white and kraft paper is yellow; The shadow of white paper is shallow, and the shadow of kraft paper is deep; White paper is torn and hairy, but kraft paper is hairless; White paper is transparent, kraft paper is opaque; White paper is thicker than kraft paper. The teacher recorded the students' findings in concise words.
Teacher: Do you have anything to add?
Health: White paper has no black spots.
Health: White paper is light and kraft paper is heavy.
4. Question:
Teacher: Do the students who listen below have different opinions on the previous speech?
Health: Kraft paper smells different, and white paper is uneven?
Health: Two kinds of paper are as thin.
Health: Kraft paper is thick. (Opinions vary)
Teacher: Other students, which view do you agree with? Raise your hand and vote.
Teacher: Which statement is correct? How do you observe the thickness of paper?
Health: I have touched it.
Teacher: Is there a more accurate method?
Health: Look, click on the desktop to compare.
Teacher: Is there a more accurate method?
Health: Measure with a ruler.
Teacher: How to measure the thickness of paper? (Methods Solve the problem of after-class measurement)
[Comment: In exchange activities, when students have a dispute about the thickness of paper, the teacher asks students to raise their hands to make more students pay attention to the controversial issue between two students-which paper is the thickness? Participate in the activity of how to compare the thickness of paper and try to solve the problem together. ]
Fourth, observe the paper fiber.
Teacher: Do you have any comments on this discovery? (The teacher points to the furry record and asks)
Health: Kraft paper has hair on one side and white paper has hair on both sides.
Health: Kraft paper has only a little hair on one side, and white paper has no hair at all. (Students are controversial)
Health: it takes a tear to grow hair. (Supplemented by the students who spoke just now)
Teacher: Do you have hair? Do you want to know? (Students think together)
Teacher: What did she say just now that they found it?
Health: tear it open.
Teacher: Can you prepare/start?
[Comment: When students can't keenly find a controversial point of view, and this point of view plays an important role in the next teaching activity, the teacher uses the record of pointing at the hair and asks: Do you have any opinions on this discovery? This can pick out contradictions and effectively attract students' attention to the observation activities of two pieces of paper fibers. ]
1. Observe the fibers of two sheets of paper:
The teacher gave the students a magnifying glass to observe, and the students quickly raised their hands to tell their findings. )
Teacher: What did you find together? (hairy)
Teacher: It seems that sometimes you can't fully understand an object from the surface, but you can only observe it from the inside.
Health: the color of hair on both sides of white paper is the same; The hair on this side of kraft paper is deeper, and the hair on this side is lighter.
Teacher: People call the hair you see fiber. Now we know what's in kraft paper and white paper. (fiber)
2. Observe more paper fibers
Teacher: Can you guess that other paper has fibers? (Will) Why?
Health: Because these two pieces of paper have fibers, the other piece of paper must have hairs.
Health: I think some papers have fibers and some papers have no fibers.
Teacher: Why? (Two students raise their hands and disagree, but they can't say why. )
Health: I think white paper and kraft paper are thinner. All the paper is made of white paper, so it should be hairy.
Teacher: Do you want to know if there are any fibers in other papers? How do I know (by observation)
Teacher: If you want to get all kinds of paper to observe, you should first ask yourself if you have any questions or guesses about observing fibers. Students ask: What is fiber made of? Why is this hair called fiber? What can fiber do? Where does the fiber come from? What is the cell structure in the fiber? Why are there fibers in the paper? I, I still have many questions about fiber ...)
Teacher: The group that got the paper began to observe more fibers in the paper (students tore the paper apart, carefully observed it with a magnifying glass, and compared it, eh. Both! The students were surprised to say that they raised their hands one after another, and there were fibers ...)
Teacher: Did you find anything else?
Health: cardboard has many fibers;
Health: I think the fibers of each piece of paper are a little different.
Health: Oh, my God! Newspapers have a lot of fibers;
Health: I think the thicker the paper, the more fiber it will be.
Teacher: What do these observations show?
Health: Different colors of paper have different colors of fibers.
Health: That is to say, paper is made of fiber.
[Comment: Observing these two kinds of activities of paper fiber greatly stimulated students' desire to observe paper. Successfully guide students from paying attention to the external characteristics of paper to observing the internal characteristic fibers of paper, so that students can understand the common characteristics of paper. Broaden the field of curriculum content.
Not limited to the study of book activities, guide students to participate more in the observation and comparison of various paper fibers in life, gain direct experience and experience in observation practice, and conduct lively inquiry learning. ]