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Bases or Alkaline Materials

by Ron Kurtus (revised 30 October 2004)

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:

• What are the characteristics of bases?
• What type of a chemical formula does a base have?
• What are bases used for?

This lesson will answer those questions. There is a mini-quiz near the end of the lesson.

Note: If you want to hear the text being read, click the Play button. It takes a few seconds for the sound to start. The voices are somewhat mechanical for computer use.

Time = 4 min. 42 sec.

Characteristics

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.

Formula

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.

Exceptions

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.

Water

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.

Summary

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.

Answers to Readers' Questions

Cover all bases

Resources

The following resources provide information on bases.

Websites

Weak Acids and Bases - from University of Waterloo, Canada

Experiments with Acids and Bases

Red Cabbage Indicator - substitute for Litmus paper

Books on chemistry

Top-rated books on Chemistry

Miscellaneous

Mini-quiz to check your understanding

1. Why should you be careful in tasting an alkaline material?

2. Which is a base?

3. What can a gardener do if the soil is too acidic?

If you got all three correct, you are on your way to becoming a Champion in Chemistry. If you had problems, you had better look over the material again.

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