What is a pH scale in chemistry?

In chemistry, pH scale is a measure of how acidic or basic a substance is. 

The pH of a substance is measured on a scale of 0 to 14. On this scale, a pH value of 7 is neutral, which indicates that the substance is neither acidic nor basic. 

A pH value of 0 - 7 indicates that the substance is acidic, with pH values nearer to 0 being more acidic than pH values nearer to 7. 

A pH value of 7 - 14 indicates that the substance is basic or alkaline, with pH values nearer to 14 being more basic than pH values nearer to 7. 

The pH scale is logarithmic. Each whole pH value below 7 is 10 times more acidic than the next higher value and each whole pH value above 7 is 10 times more alkaline than the next lower whole value. 

For example, pH 3 is 10 times more acidic than pH 4 and 100 (10 x 10) times more acidic than pH 5. 

Similarly, pH 12 is 10 times more alkaline than pH 11 and 100 (10 x 10) times more alkaline than pH 10.