 So what we then need to do is to choose a substance that's going to do this readily. Now a lot of plants, particularly flowers, are very brightly colored and the pigments in those colors can actually change depending on the pH of a solution into which they are placed. Here's an example of both some different types of indicators that you may use and also some results that were put together with red cabbage. Go back to my blue. And it shows quite a range of different colors and if our indicators are going to be useful then they need to be able to tell us a difference between acidic solutions, neutral solutions and basic solutions and to be really effective, perhaps even to distinguish between solutions that are very acidic from those that are mildly acidic or solutions that are very basic from those that are mildly basic. So you can see here we've got a range from really strong or strong-ish acid solutions at one end to very basic solutions at the other end. And here's just a couple of different examples. Red cabbage by far gives the best results and it's often the easiest one to use but it may be worth investigating if you've given the option to do this in class. Some different types of indicators, perhaps you might even want to bring some in when we go through this topic, just to test and see how effective different indicators are. Some are more effective than others but sometimes carrying out the experiment will give you an opportunity to be able to critically analyze the effectiveness of different indicators in solution. So have fun when you make this and thanks for watching.