A number of tests exist for distinguishing between acids and bases, and furthermore, between different concentrations of each family of compounds. One of those tests is pH while another is universal indicator solution.
Resources: The contents of the following PowerPoint Slides will be helpful.
- Core Acids Bases and Salts I: Definitions and Properties
- Core & Extension Acids Bases and Salts III: Acids & Oxides
Six beakers are arranged in a row. The first and the last beakers have some colored liquid in them. The contents of the first beaker are transferred to beaker 2 and then from beaker 2 to 3 and so on leaving a little bit behind each time. And then, when beaker 6 is reached the contents are transferred in reverse one after another just as before. Watch the video for the results.
And the questions are: Why did the color of the liquid change as it did when it was being transfer from 1 to 2 and down the line? Additional challenging question: Why didn’t the color change when the same procedure was carried out in reverse?
- acid, base, indicator, color, pH, dilution, concentration.