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Acids and Bases. Examples of Acids. Acids can be found in your foods. Citric acid – oranges, lemons, limes Ethanoic acid – vinegar, tomato juice Tartaric acid – grapes Tannic acid – tea Lactic acid – sour milk, yoghurt. Acids and Bases in Our Daily Lives.
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Examples of Acids • Acids can be found in your foods. • Citric acid – oranges, lemons, limes • Ethanoic acid – vinegar, tomato juice • Tartaric acid – grapes • Tannic acid – tea • Lactic acid – sour milk, yoghurt
Acids and Bases in Our Daily Lives They are all around us and are involved in many chemical processes. YUM, acid!
Examples of Acids • Other examples of acids: • Methanoic acid – insect bites, e.g. bee stings, ant bites • Hydrochloric acid – produced in your stomach • Lactic acid – produced in body during power exercises
Examples of Acids Lead-acid battery Toilet bowl cleaner Do-it-yourself cleaners Make a cleaner out of vinegar, baking soda and lemon juice! http://msucares.com/pubs/infosheets/is1436.htm
Laboratory Acids • Hydrochloric acid, HCl • Sulphuric acid, H2SO4 • Nitric acid, HNO3
Types of Acids Many naturally-occuring acids, e.g. citric acid in oranges, are sometimes known as organic acids. The other group of acids is called the mineral acids. Most of these are man-made, e.g. sulphuric acid.
What is an acid? • A substance which produces hydrogen ions, H+, when it is dissolved in water • All acids produce hydrogen ions, H+, in aqueous solution. • All acids contain hydrogen. • BUT, not all compounds containing hydrogen are acids.
Properties of Acids • Acids have a sour taste. • The word ‘acid’ comes from a latin word ‘acidus’, which means sour. • Acids are hazardous. • Irritants • Acids change the colour of indicators. • Acids turn blue litmus red – a simple test for acid. • Acids dissolve in water to form solutions that conduct electricity.
Chemical Reactions of Acids (1) • Acids react with reactive metals to form hydrogen and a salt. • Test for the presence of hydrogen • A burning splint is brought near the mouth of the test tube. • If hydrogen is present, it burns with a ‘pop’ sound.
Chemical Reactions of Acids (2) • Acids react with carbonates and hydrogencarbonates to produce carbon dioxide gas • Test for the presence of carbon dioxide • The gas is bubbled through limewater. • If carbon dioxide is present, a white precipitate is formed.
Chemical Reactions of Acids (3) • React with metal oxides and hydroxides to from a salt and water. • Neutralisation reaction
Storage of Acidic Foods • Acids are stored in glass, plastic jars or clay pots. • Acidic foods are not usually stored in metal containers because metals can react with acids.
Do you know? • Acid Bath Murder http://www.discoverychannel.co.uk/web/crime-museum-uk/episode-guide/acid-bath-murder/
So, what have you learnt today? • Examples of acids • Definition of an acid • Properties of acids • Acids have a sour taste. • Acids are hazardous. • Acids change the colour of indicators. • Acids dissolve in water to form solutions that conduct electricity. • Chemical reactions of acids • Test for gases: Hydrogen and carbon dioxide