Make your own free website on
Home | Acids, Bases and Neutral Substances | What is pH? | Plants and the Effects of pH | My Experiment | Results and Photos Trial 1 | Results and Photos Trial 2 | Discussion, Conclusion and more | Science Experiment Ideas | Links Page
* * * Plants and pH * * *
What is pH?

pH means 'power of hydrogen' and is the measure of the concentration of hydrogen ions in a solution. pH can determine whether a solution is acidic, basic or neutral.
The pH Scale
The pH scale is a scale from 0 to 14, which shows how acidic or basic a substance is. Acidic substances have a pH less than 7, basic substances have a pH over 7, and neutral substances have a pH of 7. To measure the pH of a solution you can use either a pH indicator or pH paper. 
Not all indicators determine the pH of a substance, but they can determine whether a substance is acidic, basic or neutral. Acid-base indicators indicate when an acid or base is present by changing their colour. Some indicators occur naturally in dyes in plants, while others are synthetic. Litmus for example is a natural indicator. It comes from lichens. In an acidic solution, litmus turns red and in a basic solution it turns blue. Phenol red is a synthetic indicator. In acidic solutions it turns yellowy-orange and in a basic solution it turns red.
Most indicators have only two colours. Universal indicators are a mixture of several different indicators. It can determine the pH of a solution by the variety of colours it can turn. For example if a substance with a pH of 7 was tested with a universal indicator it would turn green, and if the substance had a pH of 4 the universal indicator would turn orange.
pH paper can also be used to test the pH of a substance. The pH paper is simply dipped into the solution and the colour of the paper is matched the pH chart.


The pH scale and the pH of some common substances

Intel Young Scientist 2004