The pH scale and indicators

In a nutshell

The pH scale shows whether a solution is acidic or alkaline and the degree of acidity and alkalinity. An indicator is something that changes colour based on the solution's pH. 

The pH scale​​

• The pH scale ranges from $$0$$​ to $$14$$​​
• A pH of $$7$$​ is neutral
• Acids range from $$0$$​ to $$7$$​, with closer to $$0$$​ being more acidic
• Alkalis range from $$7$$​ to $$14$$​, with closer to $$14$$​ being more alkaline
  

1. More acidic 2. Neutral 3. More alkaline

Indicators change colour depending on pH

Litmus paper is a common indicator and can tell whether a solution is an acid or alkali but not the how strong it is. Acid turns litmus paper red and alkalis turn it blue. 

1. Litmus paper strips 2. Acidic litmus test result 3. Alkaline litmus test result

Universal indicator shows us whether a solution is acidic or alkaline and how strong it is. The colour given by universal indicator matches that of the pH chart.