Teaching objectives:
1? Through the process of guessing, exploring and verifying, students know the length unit of millimeters and decimeters, and initially establish the length concepts of 1mm and 1mm, knowing that 1cm = 10mm, 1mm = 10cm.
2? Combining the viewpoint that specific content and length units come from practice and are applied to practice, we can cultivate students' innovative consciousness and the ability to apply what they have learned to solve practical problems.
Teaching process:
First, recall old knowledge and find problems.
1? Students, the Monkey King, the Great Sage of Qitian, will visit our class today. Look, he also brought a treasure. (Multimedia playback, display literal: Look! How awesome my grandson's golden hoop is! It can be scaled, shortened to 1 cm, extended to 1 m, and even extended to the sky! )
2? Question: Did you hear what we learned? (cm, m)
3? How long does it take for students to draw 1 m and 1 cm by hand?
4? Question: If the golden hoop is shorter than 1 cm, how to express it? (blackboard title: understanding of millimeters and decimeters. )
Design intention: Students' existing mathematical experience is the cognitive starting point of learning, and it is also a "scaffold" for exploring and constructing new knowledge. Reviewing old knowledge can activate students' knowledge reserves and promote them to learn new knowledge. The Monkey King, an animated character that students are familiar with and like, is introduced into teaching, which effectively stimulates students' interest in inquiry and makes them quickly enter the active learning state.
Second, explore independently and pay attention to experience.
Activity 1: Know Millimeter.
1? Recognize it.
Guide the students to observe the ruler carefully and find that the middle of 1 cm is divided into some small cells, and the small cell of 1 is1mm.
2? Know the relationship between millimeters and centimeters.
Ask the students to count carefully what secrets they can find about millimeters. (I know that 1 cm has 10 cells and 1 mm has 10 cells.)
Blackboard: 1cm = 10mm
3? Measuring stick.
The teacher shows the stick and asks the students to estimate it first, then measure the length of their stick and compare it with the estimated length.
4? Perceived length1mm.
(1) (Show an IC card) Estimate the thickness of the IC card before measuring.
(2) Teacher's demonstration: Hold the IC card gently with index finger and thumb, and slowly pull it out with the other hand. Look at the gap between two fingers, which means it is 1mm long. Students try to compare and observe.
5? Say it.
What objects around us are suitable for the length (or thickness) in millimeters?
Design intention: Guide students to experience the process of knowledge formation, and let students perceive, experience and establish rich representations by observing, counting the scales on the ruler, measuring with their hands, comparing with their hands, and telling examples in life. Let the students strengthen the representation and establish a clear and firm concept of length in the process of comparison between estimation and actual measurement.
Activity 2: Know decimeter.
1? A preliminary understanding of decimeter.
(1) (each group sends a small stick with a length of 10 cm) Measure the length of this small stick.
(2) Through the sum of quantities, 1 decimeter is derived.
(3) Thinking: What is the relationship between decimeter and centimeter? (blackboard writing: 1 decimeter = 10/0cm)
2? Perceived length 1 decimeter.
(1) Look for it. Students find the length of 1 decimeter from the ruler and say that the length from "Ji" to "Ji" is 1 decimeter.
(2) Draw a picture. Draw a line segment 1 decimeter with a ruler. After drawing, measure the exchange capacity at the same table to see if it is accurate.
(3) measure. Please measure the length from the tip of the middle finger to the palm of your hand. This position is 1 decimeter.
3? Know the relationship between decimeter and rice.
(Show the meter ruler) Students find the length of 1 decimeter on the meter ruler and observe how many 1 decimeter are on the meter ruler. (blackboard writing: 1 m = 10 decimeter)
4? Feel a few cents.
What is the length from 0 to 20 on the meter scale? Work out how long a 2 cm meter is by hand. ) What objects around us are about 2 decimeters long? Measure the length from the tip of the middle finger to the elbow at the same table. (About 3 minutes. )
5? Observe which objects around you can be measured in decimeters and estimate how many decimeters they are.
Design intention: Through various activities, let students experience the length of 1 decimeter, and know that there are different ways to draw the line segment of 1 decimeter with a ruler, which will not only help students further understand the relationship between decimeter and centimeter, but also help them understand the diversity of problem-solving strategies. Estimation activities run through the whole teaching process, focusing on cultivating students' estimation consciousness, developing students' estimation ability and improving their estimation level.
6? Learn to use letters to represent units of length.
(1) Review: Which letter is rice? What about centimeters?
(2) Teacher's introduction: decimeter is represented by the letter dm, and millimeter is represented by the letter MM..
(3) Students try to write equations in letters. [Blackboard: 1cm= 10mm, 1dm = 1cm, 1m= 10dm.
=()cm=()mm】
Third, consolidate the practice.
Game: See who has high estimation ability.
In a group of four people, first choose the object to be estimated, each person estimates the length and tells the estimation result. Then measure, whoever estimates the result closest to the actual length will win once. After estimating for five times, do statistics, and whoever wins the most times will have the highest skill.
Design intention: pay attention to the combination of learning and application, highlight the connection between knowledge and life, and let students feel the application of length units from familiar objects.
Fourth, class summary.
Tell me what you have learned from this course. What are the disadvantages? What else do you want to say to the teacher? Any good suggestions?
Author unit
Kunming Xishan district chunyuan primary school
Editor: Li Ruilong.