SOIL PH TESTING

Plants need specific soil conditions to grow. pH is the measure of how acidic a substance is, and can be measured using an indicator; a chemical that changes colour in different pH conditions. Red cabbage contains anthocyanin, which we can extract using hot water to make a purple-blue solution. In acid (vinegar, lemon juice) it turns pink-red, and in alkaline (chalk, bleach) it turns green-yellow. As the pH depends on the chemicals within the rock the soil was made from, we can work out what the soil is made of.