2. What are acids?
Today, many people use
the Brønsted-Lowry
definition of acids: a
molecule that will give
away a proton — also
known as an hydrogen
ion — from one of its
hydrogen atoms.
This tells us that all
Brønsted-Lowry acids
must contain hydrogen.
3. What are acids?
• Acids have a sour taste. Lemons, vinegar, and sour
candies all contain acids.
• Acids have the ability to conduct electricity.
Aqueous acidic solutions are used as strong
electrolytes.
• Acids are corrosive in nature. Should be handled
with care otherwise, they can corrode our skin
• Acidic fumes will burn your nose
• Acids are mostly present in liquid or gaseous forms.
But we do have solid acids like zeolitic materials.
• Acids have a pH < 7 and are identified by shades of
red and yellow color with universal indicator
solution.
4. Reaction 1: Acids & Metals
Acids react with some metals to produce a salt and hydrogen gas.
Metal + acid → salt + hydrogen gas
The abbreviation M.A.S.H. can be used to remember this general reaction.
5. Reaction 1: Acids & Metals
When a metal is put in acid, it gets
smaller and smaller as it gets used up
in the chemical reaction.
At the same time, bubbles of gas can
be seen. The bubbles produced in the
reaction are hydrogen gas.
Example 1:
Hydrochloric acid + Calcium Calcium chloride + Hydrogen gas
HCl + Ca CaCl2 + H2
8. Reaction 1: Acids & Metals
The name of the salt formed from the reaction of a metal and acid can be
worked out using the names of the metal and the acid.
Name of metal + name of acid → salt name
1. The first word is the name of the metal
For example, a salt made when magnesium is added to an acid would have
magnesium as its first word.
2. The second word of the name is taken from the name of the acid
Hydrochloric acid → chloride
Nitric acid → nitrate
Sulfuric acid → sulfate
9. Reaction 2: Acids & Metal carbonates
Acids react with metal carbonates or metal (hydrogen) bicarbonates to give out
carbon dioxide, metal salts and water.
Acid + Metal carbonate → Salt + Water + Carbon dioxide
The carbon dioxide causes bubbling during the reaction, which is
observed as fizzing. It can be detected by passing the gas through
limewater, which will go cloudy.
Also, the reaction of metal carbonates with acids is exothermic (ie heat
energy is given out).
13. Acid Rain
Acid rain describes any form of
precipitation that contains high levels of
nitric and sulfuric acids, caused by the
air pollution of gaseous nitrogen and
sulfur oxides released by industrial
activity.
In addition to environmental harm to
forests, rivers and lakes, acid rain
heavily impacts man made structures
created from metal, sandstone and
marble.
14. Neutralisation is a chemical reaction between an acid and alkali
to form a salt and water.
Acid + alkali Salt + Water.
A salt is an ionic compound that is electrically neutral.
Reaction 3: Acids & Bases (Neutralisation)
15. Base vs Alkali
All alkalis are
bases, but only
soluble bases are
also alkalis
16.
17. Common Properties and Uses of Acids
pH < 7
Corrosive
Sour taste
Turns blue litmus paper red
Acids are proton (H+) donors
Common acids in schools are:
HCl = Hydrochloric acid
H2SO4 = Sulfuric acid
HNO3 = Nitric acid
19. Common Properties and Uses of Bases/Alkali
pH > 7
Caustic (burn/corrode)
Feels soapy
Bitter taste
Turns red litmus paper blue
Acids are proton (H+) acceptors
Common acids in schools are:
NaOH = Sodium hydroxide
NH4OH = Ammonium hydroxide
Ca(OH)2 = Calcium hydroxide
20.
21. Endothermic vs Exothermic?
Energy is stored within chemical bonds. During chemical
reactions, old chemical bonds (in the reactant) are broken
and new chemical bonds (in the product) are created.
Energy is transferred during chemical reactions.
Reactions that produce heat (energy) and transfer it to
their surroundings are called exothermic reactions.
Reactions that absorb energy from their surroundings are
called endothermic reactions.
