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ACIDS & bases. 9 Sci – Term 4. What is an Acid?. Definition: An acid is a compound that contains hydrogen ions (H + ) H + Hydrogen Ion is essentially a proton Acid’s give protons (H + hydrogen ions). Characteristics of Acids. Acids are characterised by: Sour taste
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ACIDS & bases 9 Sci – Term 4
What is an Acid? Definition: An acid is a compound that contains hydrogen ions (H+) • H+Hydrogen Ion is essentially a proton • Acid’s give protons (H+ hydrogen ions)
Characteristics of Acids Acids are characterised by: • Sour taste • Turns blue litmus paper red • Reacts with bases to form salts • Reacts with metals to form hydrogen gas If chemicals have properties of an acid, they are said to be acidic.
What is a Base? Definition: A base is a compound that contains a Hydroxide Ion (OH-). • Bases readily receive protons (H+)
Characteristics of Bases Bases are characterised by: • Bitter taste • Soapy feel – They react with natural oils on the skin to produce soap • Turn red litmus paper blue • React with acids to form salts Bases which are soluble in water are called Alkali’s. A basic solution is referred to as being alkaline.
What is Litmus paper? Litmus is made from lichen (fungus and algae/bacteria). It is a natural indicator which changes colour in the presence of acids and bases.
Examples of common Acids • Hydrochloric Acid (Gastric juice, household cleaners) • Lactic Acid (exercise build-up) • Sulfuric Acid (Drain cleaner, batteries) • Citric Acid (Fruits) • Carbonic Acid (Soft drinks) • Acetic Acid (Vinegar)
Examples of common Bases • Sodium Hydroxide (Caustic soda, soaps, detergents) • Calcium Hydroxide (Limewater) • Ammonia (Fish pee) • Sodium Bicarbonate (Bicarb Soda) • Magnesium Hydroxide (Antacids, laxatives)