A3 The pH Scale

Describe the pH scale, running from 0-14, as a scale of strength acidity and alkalinity.

The pH scale is a scale running from 0 to 14 measuring the acidity or alkalinity of a substance; 0 being the most acidic and 14 being the most alkaline. The pH scale also comes in a scale of colours, acidic being red through brown (0-6) and alkaline being the blues and purples, a neutral substance has a pH of seven and is represented by a green colour. Below is a common pH scale showing the full range from 0 to 14 and their corresponding colours.

A2 Testing for Acids and Alkalis

Recall the colours produced by the following indicators in acidic solution and alkaline solution: litmus, phenolphthalein, methyl orange and universal indicator.

Blue Litmus Paper: Blue

•          In an Alkali: No change
•          In an Acid: Turns Red

Red Litmus Paper: Red

•          In an Alkali: Blue
•          In an Acid: No change

Universal indicator: Green solution (Yellow Paper)

•          In an Alkali: Green to Purple
•          In an Acid: Red to Green
•          In a Neutral solution: Green

Phenolphthalein: Colourless

•          In an Alkali: Violet
•          In an Acid: Colourless

Methyl Orange: Orange

•          In an Alkali: Orange
•          In an Acid: Pink/Red

A1 Testing for acidity and alkalinity

Topic 5, Physical Chemistry

Recall how to test for acidity and alkalinity, using suitable indicators

There are several indicators that can be used to test the acidity of a substance. The ones that are needed in the IGCSE course are: Litmus paper (Blue and Red), Universal indicator, Phenolphthalein and Methyl Orange. Each of these colour tests are explained in the next objective (A2)

UPDATE

From now on I will be posting every single topic objective for all the Topics that are covered this year: Topic 5, Physical Chemistry and Topic 6 Electricity and Chemistry.
If I have time over the course of the year I may also write out explanations for all the previous topics and post them here. I hope this helps everyone that needs it.