Acids and alkalis
Definition
Acid: A substance that tastes sour, turns blue litmus red, and releases hydrogen ions (H⁺) in water.
Alkali: A substance that tastes bitter, feels soapy, turns red litmus blue, and releases hydroxide ions (OH⁻) in water.
Main Details
Acids have pH < 7, alkalis have pH > 7, neutral substances have pH = 7.
Acids react with metals to produce hydrogen gas.
Alkalis can neutralize acids to form salt and water.
Indicators like litmus paper, phenolphthalein, and methyl orange show whether a substance is acidic or alkaline.
Both acids and alkalis are chemically reactive and can cause burns if strong.
Examples
Acids: Lemon juice, vinegar, citric acid, hydrochloric acid.
Alkalis: Soap, baking soda, sodium hydroxide, lime water.
5 Important Points
Acids are sour, alkalis are bitter.
Acids turn blue litmus red, alkalis turn red litmus blue.
Strong acids and alkalis are corrosive; handle with care.
Neutralization produces salt and water.
pH scale (0–14) measures acidity and alkalinity.
Fun Facts
Lemon juice and vinegar are acids you eat every day.