Standard 5.a- Students know the observable properties of acids, bases, and salt solutions.

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Identifying AcidsAn acid is a compound that produces

hydronium ions (H3O+) when dissolved in water.

Ex. HCl + H2O H3O+ + Cl-

Some general properties of acids include sour taste, sticky, smells bad, reactivity with metals, and ability to produce color changes in indicators.

Acids donate H+ ions

*Sour Taste and Reactivity with metals

Foods that taste sour often contain acids

Foods that contain acids, such as tomatoes, react with metals such as aluminum.

Ex. Foils turn dark and may have holes. Food may acquire a metallic taste.

Color Changes in IndicatorsAn indicator is any substance that

changes color in the presence of an acid or base.

Litmus paper is one of the most common indicators.

Blue litmus turns red in the presence of an acid.

Red litmus turns blue in the presence of a base.

Identifying BasesA base is a compound that produces

hydroxide ions (OH-) when dissolved in water. (Bases accept H+ ions)

Ex. NaOH Na+ + OH-

Some general properties of bases include bitter taste, slippery feel, and ability to produce color changes in indicators.

Unlike acids, most bases don’t react with metals.

*Bitter TasteEx. Chocolate without sugar is

bitter. Cacao bean contains a base.Cough syrups and many liquid

medicines also contain similar bases.

Neutralization and SaltsThe reaction between an acid and a base

is called neutralization.During neutralization, the positive ions

(Na+) in an acid combine with the negative ions (Cl-) in a base to produce an ionic compound called a salt.

At the same time, the hydronium ions from the acid combine with the hydroxide ions from the base to produce water.

Neutralization and SaltsEx. Fish contains bases and is bitter.

Lemon contains acids and is sour.

Acids in lemon juice react with bases in fish, so that fish doesn’t taste bitter.