edexcel C2 topic 3

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Topic 3 ­ covalent compounds and separation techniques
Covalent compounds
A covalent bond is formed between non-metal atoms which
combine together by sharing electrons. The shared pair of electrons
holds the two atoms together and this is called a covalent bond.
Atoms bonded together in this way are called molecules.
Examples of covalent molecules
Name Structur Model
Hydrogen (H2)
Water (H2O)
Methane (CH4)
Covalent compounds are usually gases or liquid with low melting
points or boiling points and they do not conduct electricity.

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Dot and cross models
Molecule Dot and cross model
Hydrogen (H2)
Chlorine (Cl2)
Methane (CH4)
Water (H2O)
Carbon dioxide (CO2)
Oxygen (O2)
Hydrogen chloride
Covalent compounds have low melting and boiling points because
they have weak intermolecular forces even though the covalent
bonds binding the atoms are very strong. This means that only a low
temperature is needed to separate the molecules.
Covalent compounds do not conduct electricity because they have
no free electron or no ions.…read more

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Simple molecular compounds
Low melting and boiling points ­ weak intermolecular forces
Non-conductive ­ no free electron or an overall electrical
Hydrogen, ammonia, carbon dioxide, methane and water are simple
molecules with covalent bonds. They all have strong bonds between
atoms but weak intermolecular forces between molecules. When
they melt or boil it is the weak intermolecular forces that break not
the strong bonds between atoms. Simple molecular substances are
gases, Liquids or solids with low melting points and boiling points.…read more

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Graphite is an allotrope of carbon, so formed by carbon atoms
but in layers. These layers can slide over each other due to the
weak forces between layers therefore graphite is much more
softer than diamond. This means that graphite can be used as
a lubricant.
Also graphite is used in pencils because the layers slip easily
off the pencil and onto the paper and leaves a black mark.…read more

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The fact that diamond has 4 strong covalent bonds means that
there are no free electrons and ions. This is why diamond does
not conduct electricity. Also diamond is insoluble in water.
It is an allotrope of carbon and it's a type of fullerene which
are carbon atoms joined together to make a balls. The
molecule is spherical and the formula is C.
It is used as a lubricant
The tube fullerenes are called nanotubes which are strong
and conduct electricity.…read more

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Separation of liquids:
Immiscible liquids mean that liquids do not dissolve in each
other e.g. oil and water. A separating funnel is used to
separate immiscible liquids by waiting until two layers form
(denser liquid (water) sinks to the bottom and the less denser
one (oil) forms a layer at the top) then opening the tap and
letting the bottom liquid to flow out. The liquids are now
Miscible liquids mean that liquids dissolve in each other. They
are often separated using fractional distillation.…read more

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It is used to separate mixtures of colour compounds. These include
ink, dyes and food colouring.
A spot of the mixture is placed on a paper with a pencil (doesn't mix
with mixture) on the baseline of the paper. The paper is then
placed upright in a beaker containing the solvent e.g. water. As the
solvent seeps up the paper, it carries the mixture with it.
Components of the mixture will move at different rates and his
separates the mixture.…read more



Hi, do you have any c1 chemistry core notes ???

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