The pH value of a substance is determined by the concentration of hydrogen ions (H+) present in
the solution. Substances can be classified as acidic or basic depending on the concentration of
these hydrogen ions.
Acidic substances have a higher concentration of hydrogen ions, which means a lower pH value.
When dissolved in water, acidic substances release hydrogen ions, which increase the
concentration of H+ ions in the solution. Examples of acidic substances include lemon juice,
vinegar, and battery acid.
Basic substances, on the other hand, have a lower concentration of hydrogen ions, resulting in a
higher pH value. Basic substances are also known as alkaline substances. They can accept
hydrogen ions or release hydroxide ions (OH-) when dissolved in water, reducing the
concentration of H+ ions in the solution. Examples of basic substances include baking soda,
ammonia, and soapy water.
The pH scale ranges from 0 to 14, with 7 being neutral. Substances with a pH less than 7 are
considered acidic, while substances with a pH greater than 7 are considered basic. The pH scale
is logarithmic, which means that each unit represents a tenfold difference in the concentration of
hydrogen ions. For example, a substance with a pH of 3 is ten times more acidic than a substance
with a pH of 4.
In summary, the acidity or basicity of a substance is determined by the concentration of
hydrogen ions. Acidic substances have a higher concentration of H+ ions, resulting in a lower pH
value, while basic substances have a lower concentration of H+ ions, resulting in a higher pH
value.