L/O – To know how the pH scale can be used to show acids and alkalis

They all contain acids What do all these things have in common? Which do you think is the most Acidic? What would you need to find out? They all contain acids

Universal Indicator can be used to test how strong an acid or an alkali is Universal indicator changes colour in acids and alkalis Strong acids = Red Weak Acids = Orange Strong Alkalis = Purple Weak Alkalis = Light Blue Neutral = Green stronger acid stronger alkali strongacid weakacid weak alkali strongalkali neutral

pH Colour in the squares the right colour and then stick in the examples (or you can write them in if you are short of time)

pH pH 1 – car battery acid pH 4 – lemon juice; vinegar pH 6 – rain water; coke; citric acid pH 7 – water; salt pH 8 – washing up liquid pH 12 – oven cleaner pH 13 – sodium hydroxide; ammonium hydroxide

pH

Acid Or Alkali? Substance pH Description of acid/alkali soda water 6 Are the following substance acid or alkali? Are they weak or strong (pH number) Substance pH Description of acid/alkali soda water 6 car battery acid 1 soap 8 washing soda 10 stomach acid 2 oven cleaner 14 vinegar 4 very weak acid very strong acid very weak alkali weak alkali strong acid very strong alkali weak acid

Why is it important to know the pH of an alkali or acid? Acids with a lower pH and Alkalis with a higher pH are more dangerous so precautions need to be taken such as eye protection etc Less strong acids and alkalis are not as dangerous e.g. lemon juice