Acids and Bases
Keywords:
Acids
Base
Indicator
Corrosive
Neutral
Classify
What are acids?
Many people think that acids are dangerous. Some acids are dangerous, but others are harmless.
Some common everyday substances that contain acids are:
Sour Milk (Lactic Acid)
Stomach (Hydrochloric Acid)
Lemon (Citric Acid)
Acid-Base Indicators
An indicator is a compound that shows by means of a colour change whether a substance is acidic or basic.
Litmus is an example of a chemical that is an acid-base indicator.
Acids turn litmus from blue to red.
Bases turn litmus from red to blue.
If there is no colour change, we say the substance is neutral.
What are bases?
A base is the chemical opposite of an acid.
Bases that dissolve in water are called alkalis.
Like acids, some bases can be dangerous and others harmless.
The pH Scale
The pH scale is used to tell us how acidic or basic a substance is.
The pH scale goes from 0 to 14.
A solution whose pH is 7 is neutral.
A solution whose pH is less than 7 is acidic.
A solution whose pH is more than 7 is basic.
The lower the pH value below 7, the more acidic something is. The higher the pH value above 7, the more basic something is.
Measuring pH using Universal Indicator
Universal indicator changes colour depending on the pH of the solution to which it is added. The colours range from red (low pH) to green (neutral) to purple (high pH)
Universal indicator can be used in liquid or paper form. A colour chart is used to indicate the approximate pH of the solution.
Measuring pH using a pH Sensor
A pH sensor can be used to measure pH.
A probe is inserted into the solution you wish to test and the reading is displayed on the computer or smartphone.