“吨”的认识这一内容是在学生认识了质量单位“克”和“千克”的基础上进行教学的。对于“吨”这个质量单位,学生在日常生活中很少接触,所以教材通过装货物的卡车、火车皮等这样一组图片,让学生初步感知这些物品都很重,不能用以前学过的质量单位来表示,自然地引出了更大的质量单位“吨”。接着通过计算10袋大米的质量,教学1000千克是1吨这一例子,让学生实际感受到这个很大的质量单位。本 “T ” understanding of this content is based on the students to understand the quality unit “grams ” and “kg ” based on teaching. For quality units such as “t ”, students rarely touch in daily life, so the teaching materials such as trucks, train wagons and other such pictures make students feel that these objects are very heavy and can not be learned before The quality unit to be said that naturally leads to a larger mass unit “t ”. Then by calculating the mass of 10 bags of rice, teaching 1000 kg is one tonne of this example, so that students actually feel this great quality unit. this