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找一些日常用品可引导学生开发出一些很精采的小实验,下面介绍用小药瓶做的几种实验。一、找一个带铝帽的小药瓶,如先锋霉素或核糖霉素的空药瓶,用注射器向瓶内注水、洗净。找一个透明玻璃杯,盛点室温下的清水,用注射器调整注入瓶内的水量,使小药瓶刚刚能浮于水面。再用一个同样的玻璃杯,加入比清水高20℃左右的热水,将此小药瓶放入热水杯中,它沉下去了,如图1所示。让学生思考为什么?如把此小药瓶放回到凉水杯中,它又浮起来了,还可以看到小药瓶内有些雾汽。若杯中下半部放冷水,上半部放适当的热水,两者温差25℃左右,并用漏斗向下层倒冷水,使冷水和热水不能马上混合,而形成一个界面。小药瓶会悬浮在水中一段时
Finding some daily necessities can guide students to develop some very good small experiments. Here are some experiments done with small bottles. First, find a small medicine bottle with an aluminum cap, such as the empty bottle of Pioneermycin or Ribomycin. Fill the bottle with water and wash it with a syringe. Look for a clear glass, collect fresh water at room temperature, and adjust the amount of water injected into the bottle with a syringe so that the small bottle can just float on the water. Then use the same glass, add hot water that is about 20°C higher than that of clear water, put the small medicine bottle into the hot water cup, and it sinks, as shown in Figure 1. Let students think about why? If you put this small medicine bottle back into a cold water cup, it floats again, and you can see some mist inside the small medicine bottle. If the lower half of the cup is put in cold water and the upper half is put in suitable hot water, the temperature difference between the two is about 25°C, and the funnel is used to pour the cold water downwards so that the cold water and hot water can not be mixed immediately to form an interface. The small bottle will be suspended in water for a while