pH is a measurement of the acidity or basicity of a solution, with values below 7 indicating an acid and values above 7 indicating a base. The pH scale ranges from 0 to 14, with pure water having a neutral pH of 7. Accurate pH measurements can be obtained electronically using a pH meter, while approximate measurements can be made using chemical indicators that change color based on the solution's acidity or basicity. pH is an important measurement in fields like biology, chemistry, medicine, and engineering.

1. IES Auringis. Jaén.
José Cayetano Bautista Expósito
4º ESO. Physics and Chemistry. Unit 8 (II).
pH.
● pH is used to measure the acidity or basicity of a solution. The pH
measurement represents the tendency of hydrogen ions to interact
with other components of a solution.
●
Pure water(25ºC)
,considered neutral (not an acid and not base), is
pH=7 .
● Acids have pH numbers lower than 7.
● Basic (alkaline) solutions have pH numbers higher than 7.
● pH measurements are important in many fields as biology, chemistry,
medicine, civil engineering (concrete behaviour), etc.
● Measured pH values are between 0 (strong acid) and 14 (strong
alkali).
● Accurate measurements of pH can be obtained by electronic devices
called pH-meters, that measure the pH values using the electricity of
the ions in a solution.

2. IES Auringis. Jaén.
José Cayetano Bautista Expósito
4º ESO. Physics and Chemistry. Unit 8 (II).
pH.
● And approximate measure of
pH can be done using
different types of chemical
indicators that change its
colour according to the acidity
or basicity of a solution.
● Universal indicator paper is
paper that have been
impregnated with a mixture of
indicators to achieve a
continuous colour change
from about pH 2 to pH 10.