## 不寻常的粉笔学生作文

To be honest, seventh grade science and I mostly rely on "rote" The magic will be over the five hurdles. However, after entering the eighth grade, this "magic weapon" also lose control of how, and learn it is very practical; thanks to scientific experiments course aroused my interest, leaving me to get into the hands of the teacher is Shen chalk.

To "material density" a class, teacher, Shen, hand chalk told us: "If the quality of chalk Zhezhi 8 grams and measuring 4 cm 3, then its density should be the number?" Students have according to the formula (ρ = m / v) hastened to quickly calculate the density of chalk 2 g / cm 3. Suddenly, Shen teacher "popping" is heard in the hands of broken chalk, told us: "Now, I put chalk randomly divided into two parts, then the density of each part should be the number?" Teacher, Shen, the "casual" This is the word put special emphasis on tone, but also repeated several times. One after another, many students say the answer. "Yes, 2 g / cm 3!" At this time, teacher, Shen, about second-hand grip of varying lengths on the chalk, excitedly said, "because they are chalk!" Since then, the "density of the material properties, the same substance of the plot is unchanged, "this scientific knowledge will be rooted in my heart. Later, we made a determination of the density of matter in group experiments, many students put stones into two, have come to the same or similar density.

Teacher, Shen mentioned formula replicability reasoning using mathematical methods, often with red, yellow and blue chalk in turn show the hands of this teacher, Shen, colored chalk, such as beating of the notes, images, vivid, so that we are both relaxed and learn together happy; Shen teacher also used chalk powder into the suspension liquid foam, and emulsion, the solution can be compared; to chalk on the throw, drop to indicate what is the role of inertial motion and gravity; is to compare chalk down chalk placed on the desktop Pressure Size ... ... In short, each section of each lesson, the teacher's chalk Shen are Magical.

Really magic chalk! When listening to Shen's class, I always felt this way!

说实话，七年级的科学我大都靠“死记硬背”这个法宝过五关斩六将的。然而，进入八年级以后，这“法宝”怎么也不听使唤了，学起来很不踏实；幸亏科学实验课引起了我的兴趣，而使我入门的却是沈老师手中的粉笔。

上“物质的密度”一课时，沈老师手持粉笔对我们说：“假使这支粉笔的质量为8克，体积为4厘米3，那么其密度应该是多少？”同学们纷纷按照公式（ρ=m/v）对号入座,很快便算出粉笔的密度为2克/厘米3。忽然，沈老师“啪”的一声折断了手中的粉笔，对我们说：“现在，我把粉笔随意分成二部分，那么每一部分的密度应该是多少？”沈老师把“随意”这二字的语气说得特重，还重复了几遍。陆陆续续有不少同学说出了答案。“对，2克/厘米3！”这时，沈老师左右二手各握长短不一的粉笔，兴奋地说，“因为它们都是粉笔！”从此，“密度是物质的属性，同一物质的密谋是不变的”这一科学知识便在我的心里生了根。后来，我们又做了测定物质密度的分组实验，许多同学把石块一分为二，都得出了相同或相近的密度值。

沈老师讲到公式的举一反三，在用数学方法进行推理时，往往用红、黄、蓝粉笔依次展示，沈老师手中这彩色粉笔如跳动的音符，形象、生动，使我们学起来感到既轻松又愉快；沈老师还用粉笔灰泡成悬浊液，与乳浊液、溶液进行比较；将粉笔上抛、下落来说明什么是惯性运动和重力作用；正倒放置粉笔来比较粉笔对桌面压强的大小……总之，每一节每一课，沈老师的粉笔都有妙用。

真是神奇的粉笔！每当听沈老师的课，我总有这样的感受！