The pH Scale

• When substances dissolve in water , they dissociate into their individual ions
• Hydroxide ions , OH⁻ (aq) , make solutions alkaline
• Hydrogen ions , H⁺ (aq) , make solutions acidic
• The pH scale is measure of the acidity or alkalinity of an aqueous solution
• A solution with a pH of 7 is neutral
• Aqueous solutions with a pH less than 7 are acidic
• The closer a pH of zero , the stronger the acid
• Aqueous solutions with a pH of more than 7 are alkaline
• The closer a pH of 14 , the stronger the alkali
• The pH of a solution can be measured using a pH probe or universal indicator
• Indicators are dyes that change colour depending on whether they are in acidic or alkaline solutions
• Litmus changes colour from red to blue or vice versa
• Universal Indicator is a mixture of dyes that shows a range of colours to indicate how acidic or alkaline a substance is