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本文涉及小学《自然》教材中有关地层的形成的演示实验,作者在和学生进行了反复实验的基础上,根据实验现象和教材的矛盾,认为教材中存在“疏漏和不足”。尽管本文中学生的一些说法还缺乏科学性(如“砂子和黏土使这杯水的浮力增大了”),但他们不迷信权威的怀疑精神、勇于探究的精神却是值得张扬的。但本刊为了慎重起见,特地就这一问题向教材编写组请教,有关专家答复如下:“根据重力沉降的原理,密度大先沉下去,关键还要看是什么石头和砂子。也有人提出过这个问题,我们自己也亲自做过这个实验,一般来说石头在下面,石头中间的夹缝和上面是砂子。”根据专家的意见,并经深入研究教材,我们也许可以这样认为:本演示实验的重点并不在于小石子和砂子哪个先沉降到底,而在于不同的物体沉降后会发生分层现象,这即可说明地层形成的原因;而如果要讨论二者到底哪个先沉降到底的问题,密度则是一个首先要考虑的因素,本文作者使用的实验材料中砂子的密度应该比石子的密度大。相信很多老师在教学中都会遇到这个问题。我们现将此文刊出,一则鼓励老师们面对科学问题时的质疑精神和探究精神,二则以期引起老师们更多、更深入的思考和探究。
This paper deals with the demonstrations of formation formation in the “Nature” textbook of elementary school. Based on the repeated experiments with students, the author thinks there are “omissions and deficiencies” in the textbooks based on the contradiction between the experimental phenomena and the textbooks. Although some of the statements made by students in this article are still not scientific (such as “the buoyancy of sand and clay increases the water of the glass”), they do not infringe on the skepticism of authority and the spirit of courage to explore is worthy of promotion. However, in order to be cautious, we specially ask for advice on this issue from the compilation team of teaching materials. The experts replied as follows: “According to the principle of gravity subsidence, the density first descends, and the key depends on what kind of stones and sand. This problem, we ourselves have done this experiment, in general, the stone below, the middle of the stone between the cracks and the sand. ”Based on expert advice and further study of textbooks, we may think so: This demonstration experiment The focus is not on which gravel and sand first settle down, but rather that stratification occurs when different objects settle down, which explains the formation of the formation; and if one wants to discuss which one settles down in the end, the density It is one of the first factors to be considered. The density of sand in the experimental materials used by the author of this paper should be higher than the density of the stones. I believe many teachers will encounter this problem in teaching. We now publish this article, a challenge to teachers in the face of scientific questions and the spirit of exploration, the two are intended to arouse teachers to think more and more in-depth and exploration.