Natural Properties


 



What are acids?



               Acids are a group of chemicals with very similar properties. They all have a very sour taste and are capable of burning the skin, although some are much more powerful than others. Many metals will dissolve when they come into contact with acids. This is because acids can release hydrogen ions when they are dissolved in water. Strong acids such as hydrochloric, sulphuric and nitric acids release many hydrogen ions, so they react very fiercely with many substances. Acetic acid, which is an ingredient of vinegar, releases only a limited number of ions and is not a strong acid. This is the reason why it can be used safely in our food.



 



 



 





How can we identify acids and alkalis?



               Dyes called indicators show very quickly if a substance dissolved in water is acid or alkaline. One of these dyes is litmus. If a piece of paper impregnated with litmus is dipped into a solution, it immediately turns red if the solution is acid. If the solution is alkaline, the litmus turns blue.



               A similar dye is present in vegetables such as red cabbage and beetroot, and this dye changes colour in the same way during cooking. If your tap water is hard (alkaline, because it contains dissolved lime), the vegetables will be coloured a deep purplish-blue. Red cabbage and beetroot are often pickled in vinegar, as the acid in vinegar gives them an attractive deep-red colouration.



Pictures credit: google


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