Please enable JavaScript.
Coggle requires JavaScript to display documents.
Acids & Alkalis (Indicators) - Coggle Diagram
Acids & Alkalis (Indicators)
Common Indicators
Litmus : Red --- ___ --- Blue
Phenolphthalein : Colourless --- Colourless --- Pink
Methyl orange : Red --- Yellow --- Yellow
Bromothymol blue : Yellow --- Green --- Blue
Litmus
Litmus is a mixture of dyes collected from lichen.
They can be used in the solution form or be absorbed on filter paper (litmus paper).
Litmus can only indicate whether a substance is acidic or alkaline. It would not be able to provide additional information about the degree of acidity or alkalinity of the substance.
Universal Indicator
Contains a mixture of dyes and can come in the form of a solution or pH paper.
The indicator turns into different colours when it is added to solution of different acidity and alkalinity. Each colour corresponds to a pH between 0 to 14.
The pH of the substance can be ascertained by comparing the colour obtained against a colour chart.
Colour of Universal Indicator in :
Strong acid --- Red
Neutrl solution --- Green
Strong alkali --- Violet
pH Meter
pH meters contain probe that can be immersed in the solution of unknown pH.
A specific and more accurate pH value can be determined.
Natural Indicators
This includes leaves (red cabbage, red spinach), flowers (hibiscus, bougainvillea) or fruits (berries).
These plant parts contain chemical or pigments that are able to change colour depending on whether it is an acidic or alkaline solution.
Reasons these are
seldom used
:
Need to be extracted first ---> More effort required
Pigment may vary according to environment ---> Difficult to standardise the colour change