http://www.ck12.org Chapter 3. Chemical Interactions
Q:Bases are closely related to compounds called acids. How are their properties similar? How are they different?
A:A property that is shared by bases and acids is the ability to conduct electricity when dissolved in water. Some
ways bases and acids are different is that acids taste sour whereas bases taste bitter. Also, acids but not bases react
with metals. For other differences between bases and acids, as well as why they differ in these ways, read the short
article at this URL: http://www.chem4kids.com/files/react_acidbase.html
Detecting Bases
Certain compounds, called indicators, change color when bases come into contact with them, so they can be used to
detect bases. An example of an indicator is a compound called litmus. It is placed on small strips of paper that may
be red or blue. If you place a few drops of a base on a strip of red litmus paper, the paper will turn blue. You can see
this in theFigure3.99. Litmus isn’t the only detector of bases. Red cabbage juice can also detect bases, as you can
see in this video: http://www.youtube.com/watch?v=vrOUdoS2BtQ.
MEDIA
Click image to the left for use the URL below.
URL: http://www.ck12.org/flx/render/embeddedobject/5011FIGURE 3.99
Drawing of red litmus paper turning blue
in a base.Strength of Bases
The strength of bases is measured on a scale called the pH scale, which ranges from 0 to 14. On this scale, a pH
value of 7 indicates a neutral solution, and a pH value greater than 7 indicates a basic solution. The higher the pH
value is, the stronger the base. The strongest bases, such as drain cleaner, have a pH value close to 14.
Uses of Bases
Bases are used for a variety of purposes. For example, soaps contain bases such as potassium hydroxide (KOH).
Other uses of bases can be seen in theFigure3.100.
Summary
- Bases are ionic compounds that produce negative hydroxide ions (OH-) when dissolved in water.
- Bases taste bitter, feel slippery, and conduct electricity when dissolved in water.