Properties Of Bases.docx

Properties of Bases It's frequently possible to tell acids and bases apart from one another by some of their easily observed chemical and physical properties. A table of these properties is shown here:

Chemistry Property

Acid

Base

Taste

Sour (vinegar)

Bitter (baking soda)

Smell

Frequently burns nose

Usually no smell (except NH3!)

Texture

Sticky

Slippery

Reactivity

Frequently react with metals to form H2

React with many oils and fats

What Are Bases? Bases are ionic compounds that produce negative hydroxide ions (OH-) when dissolved in water. An ionic compound contains positive metal ions and negative nonmetal ions held together by ionic bonds. (Ions are atoms that have become charged particles because they have either lost or gained electrons.) An example of a base is sodium hydroxide (NaOH). When it dissolves in water, it produces negative hydroxide ions and positive sodium ions (Na+). This can be represented by the equation: NaOH →H2O OH- + Na+

Properties of Bases All bases share certain properties, including a bitter taste. (Warning: Never taste an unknown substance to see whether it is a base!) Bases also feel slippery. Think about how slippery soap feels. That’s because it’s a base. In addition, bases conduct electricity when dissolved in waterbecause they consist of charged particles in solution. (Electric current is a flow of charged particles.) 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.

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.