1. Indicators
Topic 9 – On the Menu!

2. Characteristic Chemical Properties
A chemical property describes what happens when two substances react with one another.
Example:
The reaction between a metal and an acid  bubbles (gas) are produced.
If a glowing splint is put into a test tube with oxygen gas, it will reignite.
If a burning splint is put into a test tube with hydrogen gas, it will pop (small explosion).

3. Indicators
An indicator is a substance that will react when put into contact with a specific substance.
Indicators usually demonstrate a colour change when a chemical reaction with a substance has occurred.

4. Common indicators
Here is a list of some indicators you may see in a lab:
Blue litmus paper – turns pink in the presence of an acid.
Red litmus paper – turns blue in the presence of a base.
Phenolphthalein – a clear solution that turns pink in the presence of a base.
Universal indicator paper – can be used to determine the pH of a substance when comparing the paper with a colour chart.
Cobalt chloride test paper – the paper turns pink in the presence of water (or if a substance contains water).
Lime water – a clear liquid that will become cloudy in the presence of carbon dioxide.
Sudan III – turns red in the presence of fats.
Fehling’s solution – a purple solution that when brought to a boil will turn orange in the presence of carbohydrates.
Biuret – a blue solution that turns purple in the presence of proteins.
Lugol’s solution – the solution will be yellowish-orange when there is no cornstarch present and will turn a dark purple in the presence of cornstarch