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Year 8
Chemistry
Lesson 1 Making red cabbage indicator
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Cards (16)
An acid has a pH
less than 7
An alkali has a pH
over 7
A pH of 7 is
neutral
Method for obtaining red cabbage indicator
Tear the red cabbage leaf into small pieces
Put the red cabbage into the mortar with some sand and grind it with a pestle
Put the red cabbage into a beaker and about 100cm cubed of water and heat
Filter the mixture and collect the filtrate. Save it for testing
Put a small amount of a chemical in a clean test tube, Add a few drops of the red cabbage indicator
What colour does the red cabbage indicator become after testing Sodium hydroxide (NaOH)?
yellow (pH 14)
What colour does the red cabbage indicator become after testing ammonia (NH3)
green
(pH 11-12)
What colour does the red cabbage indicator become after testing tap water (H2O)
blue (pH 7)
What colour does the red cabbage indicator become after testing Ethanoic acid (CH3COOH)
pink (pH 3)
What colour does the red cabbage indicator become after testing Hydrochloric acid (HCL)
red (pH 1)
What colour does the red cabbage indicator become after testing Sodium carbonate (NA2CO3)
green
(pH 10-11 )
What is meant by the word extraction?
The action of removing something
Why was the crushed cabbage heated with water?
The indicator is
soluble
in water and
dissolves better
in hot water.
Name the method used to separate the leaves from the solution of the indicator.
Filtration
What colour would you expect the red cabbage indicator to become in aqueous potassium hydroxide which has a pH of 13?
Yellow/green
What colour would you expect the red cabbage indicator to become in aqueous nitric acid which has a pH of 1?
red
If a solution turned the red cabbage indicator yellow, what effect would it have on Universal Indicator?
It would turn purple.