实验是为了直观准确地向学生传授知识,达不到目的的实验往往给学生造成错觉,因此,实验前的准备工作极为重要。 我在做一个简单的“二氧化碳熄灭蜡烛火焰”的化学演示实验时,竟连续三次都不成功。其原因:一是集气瓶容积小于烧杯容积,瓶中的二氧化碳虽已倒尽,蜡烛火焰才刚好转暗。显然二氧化碳未充满整个空间,是由于此时二氧化碳浓度太低,火焰不能熄灭,反而由暗转 Experiments are intended to impart knowledge to students intuitively and accurately. Experiments that fail to achieve goals often create illusions for students. Therefore, preparations before the experiment are extremely important. When I was doing a simple chemistry demonstration experiment of “carbon dioxide extinguished candle flame”, I failed to succeed for three consecutive times. The reason is as follows: First, the volume of the gas cylinder is less than the volume of the beaker. Although the carbon dioxide in the bottle has been exhausted, the candle flame just turns dark. Obviously, carbon dioxide does not fill the entire space because the carbon dioxide concentration is too low and the flame cannot be extinguished.