Published on January 22, 2008
Acids and Alkalis: Acids and Alkalis Some facts about acids and alkalis: Some facts about acids and alkalis Working safely with acids and alkalis: Working safely with acids and alkalis ALWAYS wear goggles If you get it on your skin wash it off with water immediately, then tell your teacher If you get it in your eyes, wash your eyes with water immediately, then tell your teacher ALWAYS read the Hazcard and observe the hazard warnings Use your common sense! Hazard signs to learn…: Hazard signs to learn… Acid Harmful –when swallowed, breathed in or absorbed through he skin Irritant – not corrosive but cause reddening and blistering of the skin Corrosive – attack and destroy living tissue, e.g. eyes and skin Detecting acids and alkalis: Detecting acids and alkalis We can detect an acid or alkali using an INDICATOR Indicators change colour in acids or alkalis LITMUS indicator RED in ACIDS PURPLE in NEUTRAL solutions BLUE in ALKALIS UNIVERSAL indicator – colour depends on the pH of the solution Universal Indicator and the pH scale: Universal Indicator and the pH scale Universal Indicator is a mixture of liquids that will produce a range of colours to show how strong the acid or alkali is: Stomach acid Lemon juice Water Soap Oven cleaner Baking powder Neutralisation: Neutralisation Something that is not an acid or an alkali is said to be NEUTRAL Water is an example of a NEUTRAL SOLUTION An acid and alkali will neutralise each other if the correct amounts are used: Useful acid-alkali reactions: Useful acid-alkali reactions 1) Hydrochloric acid is used in the stomach to help _______. If we eat too many “rich” foods our stomachs create too much ____ – this is called ______. This acid needs to be neutralised by taking indigestion tablets. 2) Soil is naturally acidic, mainly due to acid ____. This can have bad effects on ____ and vegetable growth, so the excess acid may need to be neutralised with an _____ or suitable fertiliser. Words – plant, digestion, indigestion, alkali, rain, acid Useful acid-alkali reactions: Useful acid-alkali reactions Food preservation – pickling involves soaking the food in vinegar which kills the bacteria which causes food to decay Hair and skin care – the best pH for skin is 5.5. Soaps containing very weak acids or alkalis can be used to get this pH level Stings – BEE stings are ACIDIC and are treated using an alkali such as calamine lotion which neutralises the acid of the sting. WASP stings are ALKALINE and are neutralised using an acid such as vinegar Soil treatment – acid rain can turn soil acidic. Some plants will not grow in acidic soil. The soil is neutralised using LIME which is an alkali Quiz on acids and alkalis: Quiz on acids and alkalis This a pH of less than 7 This could kill cells This is often used in cleaners or soap This would turn Universal Indicator red Sodium hydroxide is a common ____________ This would feel soapy on your skin This could be a corrosive This will turn universal indicator purple This would taste sour Lemon juice and vinegar are examples of weak _____ Acid, alkali or both???