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Topic 1: Basic chemistry
What is chemistry?
Chemistry is the study of the properties, composition and structure of matter, the
changes that occur in matter, and the energy that is released during these changes.
1. Important chemistry terminology
Matter- Is anything that can occupy space and has mass (it weighs
something) and volume (it take up space)
Atom- is the smallest unit of matter that cannot be broken down by
chemical means
They are made up of the following sub-atomic particle; neutron,
proton and electron
Proton- is a subatomic particle with a positive charge
Neutron- is a subatomic particle with no charge
Electron-is a subatomic particle with a negative charge
Valence electron- is the electron in the outer shell of an atom
It is determined by the main group number of an element found in
its column in a periodic table e.g Carbon is in group 4 and has 4
valence electron
Atomic number- number of protons in the nucleus of an atom
Atomic mass number- number of protons and neutrons in the
nucleus of an atom
Element- is a substance that cannot be broken down into simpler
substance by chemical means (element adhere to form a molecule)
Molecule- is a group of two or more atoms which are bond
together to form a compound (molecule can be broken down
chemically into elements they made up of)
e.g water molecule (H2O) is made up of two hydrogen atom and
one oxygen atom
carbon dioxide (CO2) is made up of 1 carbon atom and two
oxygen atom
Compound- substance that result from a combination of two or
more different elements
Periodic table- is the table of all the known elements arranged in
order of their atomic number
Isotopes- element that has equal number of proton but different
number of neutrons
1 By Mr E.C. Mabuza
,Agricultural sciences -Notes- Grade 11
Mixture- two or more substance which has been combined such
that each substance retains its own chemical identity.
e.g salt in water (salt dissolve in hot water)
Activity 1 (chemistry concepts)
1.1 Define the following concepts;
(a) matter
(b) Atom
(c) Proton
(d) Neutron
(e) Periodic table
(f) Atomic number
(g) Atomic mass number
(h) Isotope
(i) Element
(j) Molecule
Activity 2 (chemistry concepts)
1.1 analyse the flow chart below and answer the questions based on it
1.1.1 Identify the substance labelled A, B and C (3)
1.1.2 Explain the differences between an element and substance in (2)
1.1.3 Distinguish between the mixtures B and C (2)
2. The periodic table
Is the table of all known chemical elements in order of atomic number.
Elements in a periodic table are arranged in a series of rows and
columns based on shared chemical and physical properties at room
temperature (they may be gas, liquid or solid)
2 By Mr E.C. Mabuza
, Agricultural sciences -Notes- Grade 11
Interpreting a periodic table
Periodic table groups
Groups in a periodic table are numbered 1-18 from left to right
Group 1: made up of alkali metals (note: hydrogen is not
considered a metal)
Alkali metals are very reactive (most reactive group in the periodic
table)
They react violently with water
Has one valence electron
Group 2: made up of alkali earth metals
alkali earth metals are very reactive, but less reactive than alkali
metal
Has two valence electron
Differences between alkali metals and alkali earth metals
Alkali metal: have one electron in their outermost shell
Alkaline earth metal: has two outer shell electrons
Similarities between alkali metals and alkaline earth metals
They are both good electrical and heat conductors
They are the most reactive metals in the periodic table
They have low melting point compared to other metals
3 By Mr E.C. Mabuza
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