笔者在讲二氧化碳时做了一个演示实验,在集满二氧化碳的塑料瓶中加水后滴入紫色石蕊试液,紫色石蕊试液变红了,随后,给学生补充了一点紫色石蕊试液能指示酸性物质的知识。为此,学生对能指示酸碱性的物质产生了浓厚的兴趣并提出:市面上的水果或蔬菜榨成的汁液能不能检测物质的酸碱性呢?因此笔者给学生提供了以下思路:一是选择汁液较多的水果和蔬菜并将其榨成汁备用;二是选择生活中的一些常见物质如洗衣粉、肥皂水、洗衣液等按比 When I talk about carbon dioxide, I did a demonstration experiment. After adding water to a plastic bottle filled with carbon dioxide, I dropped a purple litmus solution and the purple litmus solution turned red. Then, students added a little purple litmus solution Can indicate the knowledge of acidic substances. To this end, students have a strong interest in substances that can indicate acid-base and asked: can the juice from the market of fruits or vegetables can detect the acid-base of the material? So I give the students the following ideas: one Is to choose more fruits and vegetables juice and squeeze juice into juice spare; the second is to choose some of the common substances in life such as washing powder, soapy water, liquid laundry detergent and other ratio