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Bases or Alkaline Materials

by Ron Kurtus (revised 16 September 2015)

Bases are chemical compounds that have a caustic action on plant and animal tissue. Sometimes a substance that is a base is called an alkali or alkaline.

You can identify a base by its characteristics and its chemical formula. The pH is a measure of the strength of a base.

Questions you may have include:

This lesson will answer those questions.


Bases are chemical compounds that have a caustic action on plant and animal tissue.

Physical characteristics

Bases feel slippery to the skin, as can be experienced with soap. Diluted bases have a bitter taste.

Of course, you should use caution when tasting or touching any chemical, especially one that is caustic to your skin.

Combining with acids

Bases will react with acids--sometimes violently--to create salts. Usually, both the base and the acid are diluted with water to buffer the reaction.

For example, a water solution of hydrochloric acid (HCl) combined with a water solution of sodium hydroxide base (NaOH) combine to form common salt (NaCl)  and water:

HCl + NaOH NaCl + H2O.

(Note: The extra water for the solutions is not included in the above chemical equation, since it isn't part of the reaction and for the sake of simplicity.)

pH strength

The pH scale is a measurement of the strength of an acid or base. A base or alkaline is a solution with a pH greater than 7.0.

Litmus paper is often used to give a rough estimate of the pH. When the paper turns red, the material is acidic, and when the paper turns blue, it contains a base.

Gardeners use the pH scale to determine how acidic or alkaline their soil is. The pH scale is also used to help determine water quality.


Bases can often be identified by the OH term in the end of their chemical formula, as seen in sodium hydroxide NaOH and potassium hydroxide KOH.


Just like with acids, there are a some exceptions to this rule. Some organic acids have formulae that make them look like bases. Acetic acid (CH3COOH) is a good example that does not follow the standard convention.

These exceptions occur mostly in organic chemistry and follow a more general description of acids and bases. In this definition Lewis Acids are those which can form a new covalent bond by accepting a pair of electrons and Lewis Bases are those that can form a new covalent bond by donating a pair of electrons.


The formula for water (H2O) can be re-written as HOH, which would make it both an acid and a base (or amphoteric substance), depending on the chemical reaction. Water is usually considered neutral.

Both acids and bases usually need to be dissolved in water to be effective.

Uses for bases

A major use for bases is in cleaning. Soaps and detergents are bases or alkalis. They also can be used to neutralize solutions that are too acidic. Industrial uses for alkalis include making new materials.

A common base is sodium hydroxide (NaOH). It is also called lye and is the grease-cutting material in early forms of soap.

If a gardener finds the soil is too acidic to grow certain plants, by noting is has a low pH, the gardener will add lime (Calcium Oxide) to make the soil neutral or alkaline, depending on how much is used. Lime is similar to chalk.


Bases are chemical compounds that have a caustic action on plant and animal tissue. A diluted base feels slippery to the skin. Its formula usually ends in OH. The pH of a base is greater than 7.0. Bases are often used in cleaning products.

Cover all bases

Resources and references

Ron Kurtus' Credentials


Weak Acids and Bases - from University of Waterloo, Canada

Experiments with Acids and Bases

Red Cabbage Indicator - substitute for Litmus paper

Chemistry Resources


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