First, teaching materials
1, teaching material analysis
"What is perimeter" is the first lesson of Unit 5 "perimeter" in the first volume of the third grade of primary school mathematics published by Beijing Normal University. The main teaching content of this section is to understand the meaning of perimeter through practical activities such as drawing, measuring and touching, so as to pave the way for understanding the meaning of perimeter of various graphics and calculating perimeter in the future. Plan to teach a class.
2. The characteristics of textbook compilation
The textbook of this lesson has the following characteristics: first, students can initially and intuitively understand the circumference of leaves by ants crawling around the edge of leaves; Then understand the meaning of perimeter through operation activities; Finally, through practical activities, let students further experience the close relationship between circumference and real life.
3. The textbook of this course embodies the mathematical ideas of "transformation" and "translation".
The method of "conversion" is an effective thinking method to study and solve mathematical problems. It is a way of thinking that uses the viewpoint of movement, change and development of things and the relationship between things to turn the unknown into the known and the complex into the simple. Exercise 3 after class infiltrates students with mathematical ideas of translation. Therefore, in teaching, we should try our best to combine the specific teaching content, infiltrate the idea of mathematical reduction, and consciously cultivate students to learn to solve problems with the idea of mathematical reduction, thus improving students' mathematical ability.
Second, students.
Students know the plane figures such as triangle, parallelogram, rectangle and square, and master the basic characteristics of these plane figures. Life will use words such as "sideline, week" to express and communicate. It may be difficult for students to understand the meaning of "length" in the meaning of perimeter during the learning process. Junior students are particularly interested in interesting learning content around them. According to the teaching content of this class and the students' reality, I pay attention to creating interesting problem situations in this class, helping students find the prototype of life, and using the teaching method of combining observation, demonstration and hands-on operation, so that students can construct new knowledge in the vivid learning process.
Three. target
1, teaching objectives
According to the teaching content of this lesson and the cognitive rules of junior three students, the teaching objectives of this lesson are determined as follows:
Knowledge and skills: know the perimeter by observing and operating specific things or graphics; Can measure and calculate the perimeter of triangle, rectangle, trapezoid and other graphics.
Process and method: Cultivate the ability of independent thinking and hands-on operation in learning activities such as "painting and touching"; Cultivate the estimation ability in the process of estimating and measuring waist circumference, and further improve students' cooperation ability.
Emotion, attitude and values: combine specific situations to perceive the close relationship between the surrounding and real life.
2. Emphasis and difficulty in teaching
According to the teaching content of this class, I determine that the teaching focus of this class is to let students understand the meaning of perimeter in specific situations; The difficulty in teaching is the measurement of the perimeter of triangle, rectangle and trapezoid.
Fourth, the method
According to the teaching content of this class and the students' reality, I pay attention to creating situations in teaching, adopt the teaching method of combining observation and demonstration with hands-on operation, and let students fully experience the formation process of knowledge and gradually establish the spatial concept of perimeter through colorful learning activities such as "drawing, measuring, touching and estimating".
Verb (short for verb) process
(A) the creation of situations, the introduction of new courses
At the beginning of the class, I created such a situation: the triangles, rectangles and trapezoids of the graphics family have been arguing about "whose circumference", and then I asked the students, "Are the students willing to help them solve it?" Greatly mobilized the enthusiasm of students, but in order to help them solve a problem, we must first understand that "what is perimeter" is naturally introduced into this class.
(2) Explore new knowledge and understand new knowledge.
1. Draw a picture, say it and feel the perimeter of the leaves.
First of all, we can understand what graphic week is in the process of drawing and speaking by using the situation of drawing leaves. Ask the students again: "Why do some students draw fast and some students haven't finished painting?" Let the students experience the length and feel the perimeter of the leaves. Then let the students use their newly acquired experience of leaf circumference as a referee to judge who the ants Beibei, Doudou and Lele climbed. It can not only make students realize that a week starts from the starting point and returns to the starting point, but also arouse their enthusiasm.
2. The concept of perceptual perimeter
On the basis of the above, ask: "Does the figure have a perimeter?" At this time, the students also have a small question mark in their hearts. At this time, I will tell the students what the circumference of a triangle is, and then immediately ask, "What is the circumference of a rectangle? What about the circumference of the trapezoid? " Then guide the students to sum up what is the perimeter of the figure.
After the initial perception of the perimeter, let the students observe the stick figure. Which figure has all straight lines whose length is exactly the circumference of the figure? Let the students understand that only closed figures have perimeter and have a complete understanding of the meaning of perimeter.
3. Measure and understand the meaning of perimeter.
After students understand the meaning of perimeter, help some friends in the graphic family to solve "whose perimeter is long?" Stimulate students' desire to learn. In addition, organize students to measure the perimeter of some figures in time, deepen their understanding of the perimeter of figures, experience and understand the concept of perimeter many times, and reflect the process of students' understanding. The most successful part in the process of teaching is to let students report different measurement methods, expand their thinking, and let students realize that the same figure may have different measurement methods.
(C) practice, the application of perimeter
1, find and touch.
Starting with familiar life cases, guide the students to find the perimeter of the surface of the object around them, and then demonstrate and point out the perimeter of the surface of the object with the students. In this way, the relationship between mathematics and life is closer, students' perceptual knowledge of perimeter is broadened, rich appearances are established and their understanding of knowledge is deepened.
Step 2 Measure and estimate waist circumference
Through the above activities, students have felt that many figures and objects have perimeters on their surfaces. At this time, tell students that girth has a wide range of applications in life-such as waist circumference. The teacher first demonstrates the method of measurement, and then lets students estimate and measure, so that students can gradually improve their estimation ability in the process of repeated estimation and measurement. Through such a series of activities, let students realize that the estimation is not a random guess, but a basis, and let students feel the connection between mathematics and real life.
(4) Improve practice and consolidate new knowledge.
Mobilize students' enthusiasm again with the situation of "there is something wrong with the graphic family" The first problem is to form two different triangles with two equal-length iron wires to judge whether their perimeters are the same. The second problem is the figure surrounded by two iron wires. (P45 3( 1)) Are their perimeters the same? Let the students know that the shapes of the figures are different, but the perimeters may be the same. Let the students solve the problems through transformation and translation.
(5) class summary
By exchanging the harvest of this lesson, stimulate students' interest in further studying the perimeter problem. Students gain not only mathematical knowledge, but also curiosity and enthusiasm for exploring the mathematical world.
(6) Transfer
After class, give the students the following assignments: Please draw a figure with a circumference of 12 cm on the square paper (each side is 1 cm). Let the students extend the knowledge they have mastered in a limited time to unlimited extracurricular activities, from classroom to extracurricular activities, and feel that mathematics comes from and serves life.
Sixth, reflection.
In the process of teaching design and trial lecture, I realized that the similarity between this teaching design and other teaching designs lies in: on the one hand, it pays attention to the close connection between mathematical knowledge and daily life. On the other hand, let students experience the process of "doing mathematics".
Compared with other teaching designs, it is innovative: the overall design embodies the educational concept of "from life to life"; Create a graphic family to argue about whose circumference is long, and use the characteristics of students' love to help others to lead to the question of "what is circumference"; Pay attention to students' experience of measurement, let students choose their own measurement methods and exchange measurement results and experiences; The homework is: draw a figure with a circumference of 12 cm on a square paper (each side is 1 cm long), so that students can extend the knowledge they have mastered in a limited time to unlimited extracurricular activities.