Transcript The_Chemical_Earth_8.2.1_

The Chemical
Earth (8.2.1)
The living and non-living components
of the Earth contain mixtures
Elements, Compounds
and Mixtures
• Elements are pure substances made up of only
one type of atom.
• Compounds are pure substances made up of
two or more atoms, chemically combined in a
fixed ratio.
• Mixtures are impure substances made up of
two or more substances, physically combined
in no fixed ratio.
Elements
At present there are 112 known elements.
88 are metals.
18 are non metals.
There are 6 semi metals or metalloids.
92 are naturally occurring the remainder are
man made
• Isotopes are elements with different atomic
masses.
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Compounds
• Compounds are made up of two or more
elements chemically combined in a fixed ratio.
• Ionic compounds are made of elements that
“give away” or “take in” electrons forming
electrically charged particles called ions.
• Covalent compounds are made up of elements
that “Share electrons”.
• Compounds have a chemical formula which
does not vary.
Mixtures
• Mixtures are impure substances because they
have no exact component parts, ie. They have
no chemical formula.
• Mixtures can be “easily” separated
Salt separated by
evaporation of sea water.
The SPHERES of the Earth
Hydrosphere – All of the water on earth
makes up the hydrosphere. Most of the water
on earth is a mixture of:
Compounds such as salt.
Gases such as oxygen.
Living matter such as plants and animals.
Particulate matter such as silt, clay, etc.
Biosphere – All life on earth makes up the
biosphere. As in the hydrosphere, the
biosphere is a gigantic mixture of life:
Plants
Animals
Viruses
Fungi
Lithosphere – makes up the crust of the earth.
Many mixtures must be separated to get
needed materials from the earth.
Metals
Fresh water
Sulfur
Artesian water
Sulfur mining
Atmosphere – The atmosphere is a mixture of
many gases, and solids:
Oxygen
Nitrogen
Helium
Dust
Separating
mixtures
• Mixtures are Physically combined combinations
of particles. This means that separations will
involve methods using the physical
characteristics of the substances and relatively
low energy input.
– Filtering/decanting – particle size
– Evaporation/distillation – boiling points
– Density – centrifugation/decanting
— Homogeneous mixture - any combination of
substances that has uniform composition and
properties; a mixture that is uniform
throughout.
Ex. Salt water, 2-stroke petrol
—Heterogeneous mixtures – any combination
of substances that does not have uniform
composition and properties; a mixture of
physically distinct substances with different
properties.
Ex. Soil and water, dust in air
Methods of
separation
• Filtration – for
heterogeneous
mixtures. Uses
particle size and a
media to
separate solids
from liquids or
gases.
Two common methods of filtration. One used
in the kitchen to separate peas, etc. from
water, the other to separate shell grit of
different sizes.
• Evaporation/distillation
– used to separate liquid
mixtures, gaseous mixtures
or liquids from dissolved
solids. With liquid
mixtures, low boiling point
liquids evaporate first
leaving higher boiling point
liquids behind. For
solutions of solids and
liquids, the liquid
evaporates leaving the solid
behind.
Laboratory distillation apparatus
Distillation of air
• Chromatography – a
method of separation
where a homogeneous
mixture such as ink is
passed along a
stationery media such
as paper using a solvent.
The paper causes
colours to “stick”
causing a separation.
Gravimetric Analysis
• This is a way of determining how much of a
material is in a mixture.
• It involves the mass of the original material, an
ore for example, and the final mass of the
mineral desired.
– Ex. If one kilo of the ore of iron, hematite,
contains 300g of pure iron oxide and 700g of
waste, the ore is 30% pure iron oxide.
See Practical – Separation techniques with this unit.
compounds
Compounds are chemically
combined arrangements
of atoms in a fixed ratio.
To separate the particles of
a compound requires large
amounts of energy, in many
cases, to overcome the
bonding strength of atoms
in the compound.
Basic Oxygen Steelmaking (BOS)
Requires huge energy input to
produce “pure” iron.
Questions
1. Write the formulas for:
1. Magnesium oxide
2. Aluminium chloride
3. Potassium sulfate
2. Categorize the following as element, compound or mixture
and justify your choice. (you may need to research each)
Water, sea water, copper pipe, oxygen, milk, smoke, petrol.
3. How does chromatography work?
4. Explain why are compounds harder to separate than
mixtures.