化学教学中,产生少量气体的反应有:原电池、电化腐蚀、电解水、电解饱和食盐水等。这些实验演示,由于可见度小,效果不好。如改用投影实验,既生动形象,又能激发学生的兴趣。而上述投影实验.只需一支培养皿就可完成。现举电解饱和食盐水为例说明其具体作法。在幻灯机的镜片上写上“阳极”和“阴极”.并相距5cm,将φ8cm 的培养皿置于幻灯机镜片上,把两个碳棒电极平放入培养中,相距3cm。并使其分别位于“阳极”与“阴极”的两侧.用玻片(或纸板)把阳极和阴极区隔开,然后在培养血中注入饱和食盐水40—50毫升(以淹 Chemistry teaching, produce a small amount of gas reactions are: the original battery, electrochemical corrosion, electrolysis of water, electrolysis of saturated salt water. These experiments show that, due to the small visibility, the effect is not good. Such as the use of projection experiments, both a vivid image, but also stimulate student interest. The above projection experiment. Only one dish can be completed. Take the electrolytic salt water as an example to illustrate the specific practices. Write “Anode” and “Cathode” on the lens of the slide projector and leave the 5cm-long Petri dish with φ8cm on the projector lens and place the two carbon rod electrodes flatly in the culture at a distance of 3cm. And place them on either side of the “anode” and “cathode.” Separate the anode and cathode zones with slides (or cardboard) and then inject 40-50 mL of saturated saline into the culture blood