1. In specific life situations, let students feel and know the unit grams and kilograms of quality, and initially establish the concepts of 1g and 1kg, knowing that 1kg = 1000g.
2. On the basis of establishing the concept of quality, cultivate students' awareness of estimating the quality of objects.
3. Through operation and observation, let students know how to use the scale, cultivate their ability to operate and solve problems, and enhance their sense of life.
Teaching emphasis: initially establish the quality concepts of kilograms and grams.
Teaching difficulties: the flexible use of kilograms and grams.
Preparation of teaching AIDS: balance scales, two balls, mung beans, pencils, eggs, apples, salt, and 2 cents coins.
School tools preparation: salt (2 bags in each group) and 2 coins (65438+ 0 coins in each group).
Instructional design:
First, import:
1, "Look":
Teacher: Who wants to play games with the teacher? Teacher and xx, in a word.
The students answered.
Ask again: How do you know?
Blackboard: Look.
2, hand weigh in hand:
Show me two balls. One is big and light, and the other is small and heavy.
Teacher: Here are red balls and basketballs. Which of the two balls do you think is heavier?
Let the students think about it and say how you feel.
Teacher: When we can't see who is more important than who is lighter, we can still use the method of "weighing". Find two things around you and weigh them with your hands. Who is heavier than who?
3. weigh it:
Want to know how much math books and classroom exercise books weigh? What can you do?
Blackboard: Weighing.
Question: What scales have you seen in your life?
Show various scales.
Take out a scale. Introduce the use of balance. 4. uncover the topic.
Teacher: Scale is an important tool to measure the weight of objects in our life. In mathematics, the weight of an object is called its mass. Today, we will know two mass units "grams" and "kilograms".
Second, understand the quality unit "gram".
Understanding of 1 and 1 g.
Teacher: The teacher has prepared 1 quarters and a mung bean here. Who do you think is closer to 1 g? Students guess.
Weigh yourself.
Note: 1 2 cent coin weighs about 1 gram. (blackboard writing)
Let the students weigh it and say 1 gram. How does it feel?
2. 1g How many mung beans are there?
Teacher: Yes, 1 gram is very light. Children, do you want to know how many grams of 1 gram mung beans are? Look carefully. Let's count them together. 1、2、3……
Yes, it turns out that 12 mung beans weigh about 1 g! Write on the blackboard.
3. Estimate the quality of a pencil.
How much does a pencil weigh?
Weigh it. A little over five grams. A pencil weighs about 5 grams.
4. Tell me which objects weigh about 1 g or a few grams.
5. Weigh math books and classroom workbooks.
Let's weigh it together. Blackboard: A math book weighs about 200 grams.
A classroom exercise book weighs about100g.
6. Take out the salt and estimate the weight of a bag of salt. Don't be too busy estimating yet. The quartet will take turns weighing.
Students estimate.
Third, understand the quality unit "kilogram".
1. How much does a bag of salt weigh? (500g) What about 2 bags? (1000g)
2, 1000 grams, we can use a larger mass unit "kilogram". Blackboard: 1kg
3. How many grams is1kg? Blackboard: 1 kg = 1000 g.
Alphabetic representation of kilograms and grams.
Teacher: "kilogram" can be represented by the letter "kg" and "gram" can be represented by "g" We can also write 1kg= 1000g.
Read it.
Teacher: Listen to the teacher. Read with the teacher.
4. Take out 1 kg of apples.
Teacher: Look, here is a bag of apples, which weighs about 1 kg. Count, how many? Blackboard: Five apples weigh about 1 kg.
5. Tell me about those objects in life that weigh about 1 kg?
6. Estimate the quality of your schoolbag.
7. Find a child of medium height and let him talk about his weight. Find a child and a child and ask the students to estimate their weight.
Fourth, practice.
1, fill in the appropriate mass unit.
An egg weighs about 50 (
)。
The teacher weighs about 55 (
)。
A barrel of oil weighs about 5 (
)。
A dictionary weighs about 250 (
)。