INTRODUCTION TO CHEMISTRY
COMMON CHEMICALS IN DAILY LIFE
Chemical
|
Uses
|
Sodium chloride
|
• Used in preserving
food
• As table salt |
Oxygen
|
For respiration and
combustion
|
Carbon dioxide
|
Used in making
carbonated drinks
|
Ethanoic acid
|
• Used in preserving
food
• As vinegar |
Calcium carbonate
|
Used in flooring in
form of marble
|
Copper
|
• Made into wires
• Mixed with nickel to make coins |
Sodium bicarbonate
|
Used in baking powder
|
Calcium oxide
|
Used in preparation of
cement and mortar
|
VARIABLE
1.
A variable is a factor that affects the result of an experiment.
2.
For example, the mass of salt that can dissolve in water depends
on the volume and the temperature of the water. Volume and temperature are
called variables.
3.
There are three types of variables :
·
Manipulated variable - a variable that is changed during the experiment.
THE STRUCTURE OF ATOM
CONVERSION OF ENERGY
Change
of state
|
Process
|
Change
in energy
|
Solid to liquid
|
Melting
|
Heat energy is absorbed
|
Liquid to gas
|
Boiling / Evaporation
|
Heat energy is absorbed
|
Solid to gas
|
Sublimation
|
Heat energy is absorbed
|
Liquid to solid
|
Freezing
|
Heat energy is released
|
Gas to liquid
|
Condensation
|
Heat energy is released
|
Gas to solid
|
Sublimation
|
Heat energy is released
|
SUBATOMIC PARTICLE
1.
Proton number is the number of protons in the nucleus of an
atom.
2.
Nucleon number is the total number of protons and neutrons in
the nucleus of an atom.
RELATIVE MASS
1.
Relative atomic mass of an element is the number of times one
atom of the element is heavier than one – twelfth the mass of one carbon-12
atom.
2.
Relative molecular mass of a compounds the number of times one
molecule of the compound is heavier than one – twelfth the mass of one
carbon-12 atom.
PERIODIC TABLE OF ELEMENTS
PERIODIC TABLE
1.
Elements with the same number of valence electron are arranged
in the same group. Thus, they exhibit similar chemical properties.
2.
The period of an element is placed in is equal to the number of
shells occupied with electrons in an atom of the elements.
GROUP AND PROPERTIES
1.
Group 1: Alkali Metals
·
Reaction with water produce metal hydroxide and hydrogen gas.
·
Reaction with oxygen produce metal oxide.
·
Reaction with halogen produce halide salts.
2.
Group 17 : Halogens
·
Reaction with water produce acid solution.
·
Reaction with alkali metals produce halide salts.
·
Reaction with hot iron wool produce brown iron(III) halide
salts.
3.
Group 18: Noble Gases
·
Helium is used in filling hot air balloon.
·
Neon and argon are used in light bulbs.
·
Krypton is used in camera flashbulbs.
·
Radon is used to treat cancer patients
CHEMICAL BONDS
FORMATION OF IONIC BOND AND COVALENT
BOND
Ionic
Bond
|
Covalent
Bond
|
|
Type
of material
|
Between metals (Group
1,2 and 13) and non-metals (Group 15, 16 and 17)
|
Between non-metal and
non-metals (Group 14, 15 and 16)
|
Electron
|
Electron is released by
metal atoms and received by non-metal atoms
|
Electrons are shared
between non-metal atoms
|
Type
of particle produced
|
• Metal - positive ion
• Non-metal - negative ion |
Neutral molecule
|
How
to predict the formulae
|
Determine the charge of
the ions and criss cross
|
Determine the number of
electrons needed to achieve stable duplet / octet electron arrangement and
criss cross
|
Formation
of bonds
|
Strong electrostatic
forces of attraction (ionic bond) between positively charged ion and
negatively charged ion
|
· Strong covalent bond held the atoms in the
molecules
· Weak Van der Waals forces held the
molecules
|
Example
|
•
Lead(ii) bromide, PbBr2
• Sodium chloride, NaCl |
•
Naphthalene, C8H10
• Acetamide, CH3CONH |
PROPERTIES OF IONIC COMPOUND AND COVALENT COMPOUND
Ionic
Bond
|
Covalent
Bond
|
|
Melting
and boiling point
|
High melting and
boiling point
|
Low melting and boiling
point
|
Electrical
conductivity
|
Conduct electricity in
molten or aqueous state
|
Cannot conduct
electricity at all state
|
Solubility
|
Soluble in polar
solvents
Insoluble in organic solvents |
Soluble in organic
solvents
Insoluble in polar solvents |
Volatility
|
Non-volatile
|
Very volatile
|
ELECTROCHEMISTRY
1.
Electrochemical Series
i.
Electrochemical series is an arrangement of metals based on the
tendency of each metal atom to release electrons to form positive ions.
ii.
It can be constructed based on :
·
Potential difference between two metals
·
Ability of a metal to displace another metal from its salt
solution
iii.
Importance of the series :
·
To determine the terminals of voltaic cells
·
To determine the standard cell voltage
·
To determine the ability of a metal to displace another metal
from its salt solution
2.
Electrolysis in Industry
a. Electroplating
·
The electroplating metal is made the anode.
·
The object to be electroplated is made the cathode.
·
The electrolyte consists of the electroplating metal
b. Purifying
metal
·
The impure metal is made the anode.
·
The piece of pure metal is made the cathode.
·
The electrolyte consists of the metal to be purified.
c. Extraction
of reactive metal
·
Metals which are above carbon in the reactivity series are
extracted using electrolysis of the molten metal oxide or salt.
·
The metal ions move to the cathode and discharge by receiving
electrons.
ACIDS AND BASES
ACIDS
1.
Acid is a chemical substance which ionizes in water to produce
hydrogen ions, H+ or hydroxonium ions, H3O+.
2.
Properties of acid:
·
React with bases to form salts and water
·
React with reactive metals to form salts and hydrogen gas
·
React with carbonates to form salts, water and carbon dioxide
gas
·
Turn moist blue litmus paper red
·
Have pH values less than 7
3.
Basicity of an acid is the number of ionisable of hydrogen atom
per molecule of an acid molecule in an aqueous solution.
a. Monoprotic
b. Diprotic
c. Triprotic
BASES
1.
Base is a substance which can react with an acid to form salt
and water only.
2.
Base that can dissolve in water is known as alkali.
3.
An alkali is a substance which ionizes in water to produce free
moving hydroxide ions, OH-.
4.
Alkaline properties:
·
React with acids to form salts and water
·
Produce ammonia gas when heated with ammonium salts
·
Turn moist red litmus paper blue
·
Have pH values more than 7
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