Teaching content: understanding of negative numbers

Teaching material analysis:?

? The textbook guides students to know negative numbers through two teaching situations and onion micro-classroom videos. First of all, the daily contact temperature leads to negative numbers, showing different temperatures in six cities, so that students can understand the methods of expressing temperature with positive and negative numbers, and understand the meaning of these positive and negative numbers in combination with life. Then, by presenting the details in the passbook, guide students to understand that positive and negative numbers can represent two opposite quantities, learn to write and read positive and negative numbers, and realize the wide application of negative numbers in life. Students have some life experience in the expression of temperature and are familiar with the passbook, which is conducive to the study of negative knowledge. Teachers should closely combine life situations in the teaching process, so that students can understand the necessity of negative numbers and the specific meanings of these negative numbers in specific situations.

Teaching objectives:

? 1. Know negative numbers, understand their functions, and understand their significance in concrete life.

? 2. Master the reading and writing methods of positive numbers and negative numbers, and know that 0 is neither positive nor negative.

? 3. Learn to use negative numbers to express quantities with opposite meanings in daily life, and experience the connection between mathematics and life.

Breakthrough method:

? By combining the onion micro-classroom and the scene diagram of the teaching material, students can understand the negative numbers in life, and let them understand that negative numbers are quantities that express two opposite meanings. Generally, "+"is used to represent deposits, and "_" is used to represent expenditures. Ask students to talk about quantities with opposite meanings in daily life and how to express them with positive and negative numbers.

Teaching methods:

? Through the creation of "six-city temperature" and "passbook" scenarios and interesting onion videos, students' interest in learning can be stimulated, and two quantities with opposite meanings can be realized, and negative numbers can be understood initially. Through observation and comparison, thinking and reasoning, let students understand the application of negative numbers in life and understand the meaning of negative numbers initially.

Teaching preparation: textbook example projection, onion video, onion training questions

Teaching process:

? First, scene import

? 1. Show a small video of onion micro-classroom, and let students initially perceive negative numbers through interesting videos to stimulate their desire for learning.

? 2. Organize students to talk about examples of the amount of opposite meanings expressed in daily life.

? 3. Introduce new lessons, such as "_3", and add "_" before the numbers. We call it a negative number. Today, let's learn about negative numbers together.

Second, the new interactive award.

(A), the meaning of the initial feeling of the opposite quantity

1. Exchange discussion.

What does (1)0C mean?

(2) What do 3C and 3c mean?

2. Organize the report.

(1)0C indicates the temperature at which fresh water begins to freeze. The temperature below 0C is called sub-zero temperature, and "one" (negative sign) is usually added before the number; The temperature above 0℃ is called the temperature above zero. Add "+"(plus sign) before the number, which can generally be omitted.

②——3C means minus 3 degrees Celsius, and the pronunciation is minus 3 degrees Celsius; +3 C means 3 degrees celsius above zero, which is pronounced as plus 3 degrees celsius. It can also be written as 3 C and pronounced as 3 degrees celsius.

3. Understand the specific meaning when negative numbers represent temperature.

(B), to further perceive the amount of the opposite meaning

1. Example 2 on page 3 of the textbook.

(1) Courseware shows the projection of Example 2.

The teacher introduced the relevant information in the passbook with a projection.

(2) observation and thinking.

Question: "Expenditure (1)" in the table. "In 2000, there were four figures. 00,-500.00,-132.00,500.00 "is in the depositor column (+). Do you know what these numbers mean?

(3) Organize communication.

"2000.00" means that the depositor has 2000 yuan; "A 500. 00 "indicates consumption of 500 yuan; "One 132.00" means expenditure 132 yuan; "500.00" means depositor 500 yuan.

2. Inspire thinking.

Question: Look at the numbers "A 500.00" and "500.00". What do you find?

Students may have the following findings:

(1) "-500" and "500" do not count. The words are all the same, except that one has a "one" in front of it and the other doesn't.

(2) These two figures have completely opposite meanings, one is deposit and the other is expenditure.

3. Summary

In order to express two opposite quantities, such as temperature above zero and temperature below zero, income and expenditure need two numbers. One is that the numbers we have learned before, such as 3500, 4.7, 5 and 8, are all positive numbers; The other is to add a "one" number with a negative sign before these numbers, such as -500, -4.7, -3, etc. These figures are negative.

4. How to read positive and negative numbers?

How to read negative numbers: read "negative" first, then read it. For example, one-third is pronounced as negative three, and -3/8 is pronounced as negative three-eighths.

Pronunciation of positive numbers: the "ten" in front of positive numbers can be omitted; If you want to compare with a negative number, you can also add a plus sign, such as +3, which is pronounced as +3.

5. About 0.

(1) Organize students to discuss and exchange: Is 0 a positive number or a negative number?

On the basis of students' reports, let students know that 0 is neither positive nor negative, it is the dividing point between positive and negative numbers.

Here, students can also experience it with concrete examples, such as: 0C on the thermometer is the dividing point between above zero and below zero; In the passbook, 0 yuan said that there were neither depositors nor expenditures.

Third, consolidate the practice.

1. Onion classroom exercises

2. The fourth page of the textbook "Doing", the first 1 topic, the second topic.

Fourth, class summary.

What did you get from this lesson?

In this lesson, we learned negative numbers. In daily life, there are often two quantities with opposite meanings, such as profit and loss, the number of people getting on and off the bus, income and expenditure, the number of floors above and below the ground, the fluctuation of water level and the distance in opposite directions. At this time, we can use positive and negative numbers to express it. 0 is neither positive nor negative.