第二单元:千克和克

第1课时 千克的认识

教学内容:第28~30页,千克的认识

教材简析:初步感受物重,知道秤可以称物重,感受1千克和几千克,知道几千克是计量物体重量的单位。

教学目标

1.通过创设情境,使学生感受并认识质量单位千克,初步建立千克的概念;

2.使学生通过观察、操作,让学生了解称物体的方法;

3.培养学生动手能力,增强学生学习数学的兴趣,学习与他人合作交流。

重点难点:体会1千克是多重

课前准备

教师:课件、台秤一个、两袋质量不一样的食品、若干重1千克的物品、若干其他重量的物品

学生:称好自己的体重、带1千克重的物品

教学过程

一、导入新课

情境:同学们,你们都喜欢去商店买东西吧!你买过些什么?这是老师昨天在超市买的两袋东西(出示:两袋不同重的食品)

1.猜一猜:哪一袋重一些?

2.掂一掂:哪一袋重一些?

要知道食品准确的重量该怎么办呢?(用秤称一称)这节课我们就来学习用秤称物品

二、学习新课

1.课件演示:介绍认识生活中常见的秤

2.认识台称,学习使用台秤称物品的方法

(1)引导学生看图:在秤面上你看到了什么?(指针、刻度)秤面上的刻度告诉我们物品重多少,像物体的长度单位是米一样,物品重多少也有他的单位,国际上通用“千克”来作它的单位(板书:千克),千克在我们生活中又叫什么?(公斤)

(2)千克常用字母kg表示。(板书:kg)秤面上一大格就表示1千克,指针指着数字1,也就是说这袋红枣重1千克。你能在秤面上找出2千克、3千克、4千克、5千克吗?……

3.动手试一试

(1)小组合作派一人称出重1千克的盐装在袋子里,用手拎一拎,说说你的感受,并记在心里

(2)把自己带的秤好的1千克的东西比一比是不是与1千克盐一样重,体会出1千克到底有多重

(2)请带了1千克水果的同学数数这1千克水果有几个。

(3)情境:老师这儿有许多东西,你能从中找出1千克重的吗?

4.估一估

(1)请你猜一猜老师体重大约有多少千克?看一看、抱一抱

(2)同学间相互估计对方的体重有多少千克,再把自己的真实体重告诉猜的同学,看谁估得准

三、巩固练习

基础训练:

1.想想做做1

谈话:通过称一称,我们知道表示物品有多重都可以用千克作单位。

出示商品实物照片,观察后交流从图中获得的数学信息。

问:你知道什么是净含量吗?

2.想想做做2

谈话:生活中处处都可以看到关于重量的信息。

出示图片,了解数学信息。

从这两幅图中,你知道了什么?(进行安全教育)

3.想想做做3

学生观察秤面说出各种蔬菜的重量。

交流反馈,让学生说说是怎样看出秤面上所表示的物品重量的。

根据刚才说出的数据提出数学问题,口答解题。

4.“你知道吗?”

让学生进行阅读,然后交流自己的体会,使学生感受计量单位千克在生活中的广泛应用。

作业设计:

我会填

(1)要知道物品有多重,可以用手(  ),用秤(  )

(2)称物品有多重,一般用(  )做单位。

(3)(  )千克可以用符号kg表示,它又叫做(   )

四、总结延伸

这节课你学到了什么?有什么收获和体会?

谈话:千克在生活中的应用是广泛的,希望同学们课后到商店去看一看,记一记,哪些物品重1千克,星期天和妈妈一起到菜场去买菜,看一看妈妈买了哪些菜,各重几千克,试试你能帮妈妈拎起几千克重的物品。

板书设计

                千克的认识

              掂一掂 称一称 看一看

              千克(公斤)KG

             17个鸡蛋的重量大约是1千克。

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