表象是事物不在面前时,人们在头脑中出现的关于事物的形象。因此表象是外物的呈现方式,它不同于知觉,知觉只有当对象作用于感官时才存在,表象则可以在这种作用消失后继续存在,而表象在人的头脑中的建立是需要经历“感知—运用—积累”的过程的。在小学数学教学中,长度单位、重量单位、时间单位等的概念课都属于表象建立教学。其中长度测量因其在生活、学习中的广泛应用,一直是测量教 Appearance is the appearance of things in the mind when things are not in front. Therefore, the appearance is the appearance of foreign objects. It is different from perception. Perception exists only when the object acts on the senses. The appearance can continue after the disappearance of the effect. The appearance of the appearance in the mind of the human requires the experience “Perception - use - accumulation” process. In primary school mathematics teaching, the concept of length units, weight units, time units and other concept classes belong to the image of the establishment of teaching. One of the length measurement because of its extensive use in life, learning, has always been measured