MATERIALS
MODULE 01a (ii)
PARTICULATE NATURE OF MATTER
The particulate nature of matter
Demonstrate understanding of the
terms atom and molecule.
• An tom is a single particle (although it is made
up of sub particles)
• Molecules are made up of several atoms
• These can be the same or different.
ATOMIC THEORY
•Everything is made up of either
atoms or molecules
•Molecules are made of atoms
•Atoms are made up of three small
particles
Elements, compounds and mixtures
Describe the differences between
elements, compounds and mixtures
• http://www.chem.purdue.edu/gchelp/atoms/
elements.html
An element
• consists of only one kind of atom,
• cannot be broken down into a simpler type of
matter by either physical or chemical means,
• can exist as either atoms (e.g. argon - Ar) or
molecules (e.g., nitrogen – N2).
A compound
• consists of atoms of two or more different
elements bound together,
• can be broken down into a simpler type of
matter (elements) by chemical means (but not
by physical means),
• has properties that are different from its
component elements, and
• always contains the same ratio of its
component atoms.
A mixture
• consists of two or more different elements
and/or compounds physically intermingled,
• can be separated into its components by
physical means, and
• often retains many of the properties of its
components.
Demonstrate understanding of the concepts of
element, compound and mixture
• http://www.bbc.co.uk/schools/ks3bitesize/sci
ence/chemical_material_behaviour/compoun
ds_mixtures/activity.shtml
Physical and chemical changes
Physical and chemical changes
Identify physical and chemical changes, and
understand the differences between them
• A chemical change makes a substance that
wasn't there before.
• There may be clues that a chemical reaction
took place, such as light, heat, colour change,
gas production, odour, or sound.
• The starting and ending materials of a physical
change are the same, even though they may
look different.
•
http://www.grandinetti.org/Teaching/Chem121/Lectures/MatterAndMixtures
Chemical changes
• take place on the molecular level.
• produce a new substance.
• Examples of chemical changes include
combustion (burning),
cooking an egg,
rusting of an iron pan,
mixing hydrochloric acid and sodium hydroxide
to make salt and water.
Physical changes
•
•
•
•
are concerned with energy and states of matter.
do not produce a new substance.
Examples are
are changes in state or phase (melting, freezing,
vaporization, condensation, sublimation)
• Examples of physical changes include
crushing a can,
melting an ice cube,
breaking a bottle.
Experimental techniques
• http://www.bbc.co.uk/schools/ks3bitesize/sci
ence/chemical_material_behaviour/compoun
ds_mixtures/revise9.shtml
• This is a very good website
Describe paper chromatography.
• Chromatography can be used to separate
mixtures of coloured compounds.
• Mixtures that are suitable for separation by
chromatography include inks, dyes and
colouring agents in food.
The colours separate and move up the
paper at different rates
Interpret simple chromatograms.
• Simple chromatography is carried out on paper.
• A spot of the mixture is placed near the bottom
of a piece of chromatography paper and the
paper is then placed upright in a suitable
solvent, eg water.
• As the solvent soaks up the paper, it carries the
mixtures with it.
• Different components of the mixture will move
at different rates. This separates the mixture
out.
• The same substance will always move the
same distance if the same solvent is used
• Chromatography can be used to analyse which
substances are present in a mixture
Describe methods of separation and purification:
filtration, crystallisation, distillation, fractional
distillation
• Mixtures of liquids can be separated according
to their properties.
• The technique used depends on whether the
liquids dissolve in each other, and so are
miscible,
• or if they are immiscible.
• Fractional distillation is a technique used to
separate liquids according to their boiling points.
Immiscible liquids
• Immiscible means that the liquids don't dissolve in
each other –
• oil and water are an example.
• It is possible to shake up the liquids and get them
to mix but they soon separate.
• Separating immiscible liquids is done simply using a
separating funnel.
• The two liquids are put into the funnel and are left
for a short time to settle out and form two layers.
• The tap of the fun
• nel is opened and the bottom liquid is allowed to
run. The two liquids are now separate
• Separating immiscible liquids
is done simply using a
separating funnel.
• The two liquids are put into
the funnel and are left for a
short time to settle out and
form two layers.
• The tap of the funnel is
opened and the bottom
liquid is allowed to run.
• The two liquids are now
separate
Miscible liquids
• Miscible liquids are harder to separate as they
dissolve in each other.
• Miscible liquids are often separated using
fractional distillation.
• This is possible as miscible liquids have
different boiling points.
Ethanol and water
• Simple
distillation can
be used to
separate these
• The ethanol
evaporates then
condenses
• It is then
collected
• Water remains
in the flask
Fractional distillation of liquid air
• Air is cooled
• Water vapour condenses, and
is removed using absorbent
filters
• Carbon dioxide freezes at –
79ºC, and is removed
• Oxygen liquefies at –183ºC
• Nitrogen liquefies at –196ºC
• The liquid nitrogen and oxygen
are then separated by
fractional distillation.
A mixture of a solid and a liquid
• These can be
separated by
filtration
•
http://www.scs.sk.ca/cyber/elem/
learningcommunity/sciences/scie
nce10/curr_content/science10/un
ita/redon17.html
Vacuum-filtration
• Very fine filter
paper can be used
• Very small particles
filtered out
• Pulling air through
the residue will dry
it out.
• A dissolved substance can
be removed by
crystallisation
Chromatography
Filtration
Crystallisation
Simple distillation
Separating a liquid from a solution
Identify substances and assess their purity from
melting point and boiling point information.
• The melting point of a solid is constant
• Substances have unique melting points, which are measured and
recorded
• An impure substance's melting point will differ slightly from that of
the pure substance.
• Heating a solid substance, and marking the exact temperature at
which it melts, is a simple way to test the purity of the compound.
• Much like solids, liquids can be tested with the application of heat.
• The boiling point of liquid substances is constant
• To determine the purity of a liquid substance, chemists measure the
exact temperature at which the liquid begins to boil and compare it
with the pure substance's constant boiling point
Fractional distillation
Suggest suitable purification techniques, given
information about the substances involved
• You need to be able to apply these techniques
to appropriate situations
Understand the importance of purity in substances in
everyday life, e.g. foodstuffs and drugs.
• A pure compound contains a single chemical and is
not polluted with any other chemical or element.
• Calculating the purity of a substance is particularly
important for medicinal substances, as impurities
could injure or kill patients.
• Substances with significant impurities may produce
unexpected reactions in a laboratory setting,
creating toxic or flammable compounds.