pH strips allow you to test the acidity of a liquid. The strips measure on a scale of 14, where seven is neutral. Lower numbers are increasingly acidic, while higher numbers are increasingly alkaline (or basic). Water, being a neutral liquid, should register a seven. If a pH strip shows that it is another number, you know that the water is not pure. pH strips are fast and easy to use.
Fill a beaker with the water that you wish to test. Make sure that the beaker is completely clean of foreign contaminants that may affect your test.
Tear off a pH strip from the pack.
Dip the strip into the water briefly. The time required depends on the brand of strips that you are using. Some strips require 20 seconds while others need only one, so read the instructions carefully.
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Remove the strip from the water after the appropriate amount of time has elapsed.
Compare the color of the strip to the chart provided with the strips. Acids are represented with warmer colors (red, orange, etc) while alkalines are represented with cooler colors (blue, green, etc).
Some strips are designed to test a smaller portion of the pH scale. Make sure you get strips that test the entire range.