Teaching content:
Page 2 ~ 4 of the second volume of Grade 6: Example 1, Example 2.
Teaching objectives:
1. Guide students to understand negative numbers in life situations and read and write positive and negative numbers correctly; Know that 0 is neither positive nor negative.
2. Make students learn to express some problems in daily life with negative numbers and experience the connection between mathematics and life.
3. Carry out patriotic education for students in combination with negative history; Cultivate students' good mathematics emotion.
Teaching emphasis: the initial understanding of positive and negative numbers and reading and writing methods.
Teaching difficulty: Understanding 0 is neither positive nor negative.
Teaching process:
First, the game import, put forward the goal
1. Game: Let's play a game to relax. This game is called "I am against me, I am against me, I am against myself". Rules of the game: If the teacher says something, please say something with the opposite meaning.
① Look left (right); ② Go ahead 200 meters (go back 200 meters); ③ The elevator goes up to the 8th floor (down to the 8th floor). (4) Uncle Li earned 500 yuan today (lost 500 yuan) (5) I got 20 points (deducted 20 points) (6) Today, the temperature is above zero 10 degrees (below zero 10 degrees) ... Can you give some examples of this?
2. Put forward learning objectives.
Second, cooperative inquiry, students show
1. quantities with opposite meanings
(1) Introduce an example.
Talk: If you continue to talk along the topic just now, you will naturally enter the mysterious kingdom of mathematics. Let's look at some examples (shown on the blackboard).
(1) Six years (2) Three people were transferred in the class this semester, and two people were transferred this semester.
② The assured store made a profit of 3,000 yuan in February and a loss of 1.200 yuan in March.
(3) Compared with the standard weight, Xiaoming weighs 3 kg and Xiaohua is light 1 kg.
It is pointed out that when these opposing words are combined with specific quantities, they become a group of "quantities with opposite meanings". (Supplementary blackboard writing: quantity in the opposite sense. )
(2) Students try
How can these quantities with opposite meanings be expressed mathematically? Try to write a statement.
(3) Students' presentation and communication (e.g. +3 -2 .........................................................................)
2. Know positive and negative numbers
(1) introduces positive and negative numbers.
Let's talk about it: Just now, a classmate wrote "+"in front of 3 to indicate that three people were transferred, and adding "-"to indicate that two people were transferred (blackboard: +3-2), which is completely in line with mathematics.
Introduction: Numbers like "-2" are called negative numbers (blackboard writing: negative numbers); The number is: minus two.
"-"has a new meaning and function here, which is called "minus sign". +is a plus sign.
Like "+3" is a positive number, pronounced as: plus six. We can add "+"before 3 or omit it (blackboard writing: 3). In fact, many of the numbers we used to know were positive.
(2) Give it a try
Please use positive numbers and negative numbers to represent another set of quantities with opposite meanings.
3. Connecting with practice and deepening understanding
(1) What do the numbers in the passbook mean? (Teaching example 2. )
(2) Combining with real life, a set of quantities with opposite meanings are given, which are expressed by positive numbers and negative numbers.
① Communicate at the same table.
② Class communication. Write it on the blackboard according to the students' speeches.
Key points: We used to know that these integers, decimals and fractions are all positive numbers, also called positive integers, positive decimals and positive fractions; Put a negative sign in front of them, and they become negative integers, negative decimals and negative fractions, collectively called negative numbers.
4. Further understanding of "0"
(1) Take a look, take a look.
Dialogue: Next, let's look at the screen: This is the temperature of some cities on a certain day in February last year (shown on the small blackboard).
Harbin:-15℃ ~-3℃
Beijing: -5℃ ~ 5℃
Shenzhen: 12℃ ~ 23℃
(Please read a negative number)
(2) Take a look and say.
Let's take a look at the temperature in the capital Beijing that day. "-5℃" is pronounced as "five degrees below zero" or "five degrees below zero", which means five degrees below zero; What does 5℃ mean?
(3) Raising awareness
Ask the students to observe the thermometer and say what they find.
On the basis of students' speeches, it is emphasized that 0℃ is the dividing point, the temperature above zero is represented by positive numbers, and the temperature below zero is represented by negative numbers. (Or negative numbers all indicate the temperature below zero, and positive numbers all indicate the temperature above zero. )
Discussion: Is "0" positive or negative?
On the basis of students' speeches, it is emphasized that "0" is the dividing point between positive and negative numbers, which is neither positive nor negative.
5. practice. p8 1
6. Teach yourself the history of negative numbers
Third, practical application, expansion and extension.
1、P4 2 p8 3
2. You know the temperature when water boils is _ _ _ _. The temperature when water freezes is _ _ _ _. The lowest temperature on the earth's surface is.
3. What does "net content: 10 0. 1 kg" mean?
Fourth, induction and summary.
Students exchange gains.