2. ACIDS
• The common acids found in laboratory or in fruits/foods
are as follows:
Strong acid Weak acids
Hydrochloric acid Citric acid
Sulfuric acid Ethanoic acid
Nitric acid Malic acid
3. PROPERTIES OF
ACIDS
• All acids, either strong or weak, have the following
properties:
- Sour taste
- Able to conduct electricity
- Corrosive if concentrated
- Able to turn blue litmus paper red
- Able to react with metals, carbonate compounds and
alkalis.
4. REACTION WITH
METALS
• The reaction between metals and acids produce salts and
hydrogen gas.
• Acid + Metal Salt + Hydrogen
• A lighted splint is used to test for the presence of
hydrogen gas. It extinguishes the splint and gives a “pop”
sound.
5. REACTION WITH
CARBONATES
• Acid react with carbonate compounds to produce salts,
carbon dioxide and water.
• Acid + Carbonate Salt + Carbon Dioxide + Water
• Limewater is used to test for the presence of carbon
dioxide gas. The limewater turns chalky when carbon
dioxide is bubbled into it.
6. REACTION WITH
ALKALIS
• Acid react with alkalis to produce salts and water only
• The reaction between acids and alkalis is called the
NEUTRALISATION reaction.
• Acid + Alkalis Salt + Water
• Universal indicator can be used to show that the solution
has become neutral after the reaction. It gives a pale green
color in neutral solutions.
7. USES OF ACIDS
Acids Uses
Sulfuric acid Used in car batteries
Hydrochloric acid Removes rust from iron and steel
Ethanoic acid Used in vinegars to preserve food
Nitric acid Used in the production of fertilisers
8. PROPERTIES OF
ALKALIS
• When dissolved in water, alkalis exhibit the following
properties:
- Soapy feeling
- Turning red litmus paper blue
- Able to conduct electricity
- Corrosive if concentrated
- Reaction with acids to form salt and water.
• The common alkalis used in the school lab are sodium
hydroxide, potassium hydroxide and ammonia.
9. USES OF ALKALIS
Alkalis Uses
Calcium hydroxide They neutralize excess acid in soil
Aluminium hydroxide Used in antacid(or indigestion
tablet)
Magnesium hydroxide Used in antacid and toothpaste
Sodium hydroxide Used in making soaps and
detergents
10. PH SCALE
• The pH scale is a measure of the relative acidity or
alkalinity of a solution.
• Strong acid weak acid Weak alkali strong alkali
12. INDICATOR
• An indicator is a mixture of substances which shows
different color in different pH values of solutions.
• Universal indicator is an indicator which contains a
mixture of substances that are able to give different colors
corresponding to different pH values.
• It can be used to determine the strength of acids and
alkalis by observing the change of its color.
• The table below shows the colors of Universal Indicator
corresponding to the pH scale:
pH scale 0-2 3-4 4-6 7 8-11 12-14
Color of Universal Red Orange Yellow Pale Green Violet
Indicator green -blue
13. INDICATOR
• Other types of indicator commonly used in the lab:
Types of Acidic Neutral Alkaline
indicator
Litmus Red - Blue
Phenolphtlein Colourless Colourless Pink ( > pH 9)
Methyl Orange Red (< pH 3.5) Yellow Yellow
