Acid vs. Alkali (pH Levels)

Yesterday we received a few more of my books in the post and they are great :) I was so excited that I could not wait to finish my work so that I could look at them :)

The books were all part of "The World of..." series by Letts.

These books are KS3 books for later in the year but I was very keen to look at the Science one, so we had a look this morning. The topic that I found most interesting was the section on Acids and Alkalis, Indicators and Neutralisation. It was intriguing and easy to understand. I am going to put what I learnt into one of my presentations.

After that we did some kitchen science..... we put some vinegar (pH4) onto a saucer and some detergent (pH11) onto a saucer. Then we used so natural indicators.

Natural indicators are substances that change colour eg. beetroot, black tea, blackberries, turmeric, cherries and onion skins.

We used borage flowers. When you place borage flowers in vinegar which is acidic, they change from blue to pink. This confirmed something to me that had been puzzling me for a while. At the local plant nursery a few weeks back, I noticed that most of the borage plants had pink flowers. Normally borage has blue flowers. I have been keeping this in my mind and today when we were looking at indicators, I had an idea.

Some plants will only thrive in acid soil eg heather. The flowers of the hydrangea plant are also natural indicators. When grown in alkaline soil the flowers are pink and when grown in soil free from lime (alkaline) the flowers are blue.

So my idea was that the soil at the local plant nursery must be acidic and the borage plant / flower must be a natural indicator. The reason I thought that the soil at the nursery must be acidic is that we live in an area where there is a lot of heather. That means that the soil must be acidic! So we thought to test a borage flower to see if it would change colour in an acidic liquid and it did! Obviously the colour changes are unique, depending on the natural indicator used but for borage it seems that acidic soil or acidic liquid turns the flowers pink!

This was an amazing discovery and I am very excited about it.

We are also going to look at some of the other natural indicators and get hold of some hydrangea's.



Then we went onto the internet and looked at ebay.co.uk and bought some litmus paper (for testing pH). Litmus changes red in acid solution and blue in alkaline solution. Litmus is an indicator made from lichen, a plant that grown on the bark of trees etc) We also got some universal indicator. Universal indicator is a mixture of indicators that changes colour according to pH of the solution. We also got some methyl orange (turns red in acid and yellow in alkali).

Here is a link on more info on this topic (ACID/ALKALI) http://www.instruction.greenriver.edu/knutsen/chem160/indicatr.html