Mixtures in Industry
Grade 7 Science: Pure Substances and Mixtures
Ms. Willis
Mixtures in Industry
 Learning Goal: To identify some industry
applications of separating mechanical mixtures
and solutions.
Mixtures in Industry
 Many industries separate mixtures to produce
pure products. We are going to study three
industries that separate mixtures:
 1. The flour industry
 2. The petroleum industry
 3. The nuclear power industry
Making Wheat Flour
 2 Steps are used for making wheat flour:
 1. Purifying the wheat grains
 2. Grinding the Wheat Grains
Making Wheat Flour: Step 1 - Purifying
the wheat grains
 Wheat flour must be made
from wheat grains and
nothing else. The grains
are first passed through a
sieve which removes sticks
and stones. Then a
vacuum sucks up lighter
impurities such as dust
and leaves. Magnets pick
out pieces of iron and steel.
Making Wheat Flour: Step 2 - Grinding
the Wheat Grains
A wheat grain has 3 main
parts: endosperm, bran and
wheat germ. In a process
called “milling”, metal
rollers break open the wheat
grains, then the mixture is
passed through a series of
sieves to separate the
endosperm, bran and germ
from each other.
Making Wheat Flour
 Endosperm is used to make white flour. Bran
and wheat germ are often sold separately and
added to breads, muffins, etc. Bran and wheat
germ adds fibre and nutrients.
 Whole-wheat flour is a mixture of all three parts
of the wheat grain. Eating products made from
whole wheat flour is a healthy choice because it is
less processed and contains more nutrients.
Refining Petroleum
 Petroleum, or crude oil, is a homogeneous
mixture of many pure substances found deep in
the ground. As we have learned before, many
products in our everyday lives are made from
petroleum: plastics, asphalt, medicines, synthetic
fibers and fertilizers are some examples. We also
use petroleum to make fuel for vehicles and to
make heat.
Refining Petroleum
 Petroleum comes out of the ground as a thick,
liquid mixture of many different substances.
 Each component of the mixture boils at a different
temperature.
 Engineers have developed a technology to
separate the various components.
Refining Petroleum
A furnace heats the
petroleum until its
components begin to
evaporate. The hot gases
rise through a tall column
that cools the gases.
Different components of
the gas cool at different
temperatures. The liqud
collected at each level is
called a “fraction”.
Petroleum Refining and the Environment
 Risks of refining petroleum:
 Spilling during shipping (risk to land and/or water)
 Leaks during refining process (released into air)
 Risk of explosions and fire
 Bad smell and noise
Uranium and Nuclear Power
 Ontario uses a lot of electricity for heating,
cooling and powering machines and electrical
devices. We use several energy sources for this
including running water, fossil fuels and
uranium. About half of Ontario’s energy comes
from nuclear power.
 In each case an electrical generator (a machine
with moving parts that produce electricity when
they spin) converts the energy into electricity.
Uranium and Nuclear Power
 The inside of a generator:
Uranium and Nuclear Power
 Uranium is a radioactive substance.
 Radioactive: a term used to describe pure substances
whose particles naturally split into smaller particles,
releasing energy as they break apart.
 The release of energy is called nuclear energy. This
energy is used to generate electricity in a nuclear
power plant.
 Nuclear energy: the energy released when the
particles of a pure substance like uranium split apart.
Uranium and Nuclear Power
Uranium and Nuclear Power
 Nuclear power plants are usually easy to identify due to their
distinctive cooling towers:
Uranium and Nuclear Power
 How are the uranium particles split?
 Uranium occurs naturally in rocks called uranium ore.
It is separated from the ore by crushing the ore and
adding a solution that dissolves the uranium. The
waste rock is sieved out and uranium-containing
solution is collected.
 The water is evaporated from the solution, leaving a
solid. This solid is further processed into pure
uranium pellets.
Uranium and Nuclear Power
 Inside a nuclear power plant, the uranium pellets
are placed in the centre, or core, of a nuclear
reactor where the uranium particles are split
apart and energy is released.
 The energy heats water surrounding the core.
This water is turned into steam which turns
blades of a turbine which power generators to
produce electricity.
Uranium and Nuclear Power
 The glow caused by
intense radiation. The
high-energy particles
ejected into the
surrounding water or air
by an intense radioactive
source such as this nuclear
reactor core produce a
ghostly bluish glow.
Uranium and Nuclear Power
 When a certain fraction of uranium particles has
split, the energy production slows down and the
used particles need to be replaced with new
pellets.
 Over 90% of used uranium is reprocessed and
used again in a nuclear reactor. The remainder
must be disposed of.
Uranium and Nuclear Power
 Advantages of nuclear power:
 1. It does not produce air pollution that causes acid
rain.
 2. It does not release carbon into the environment that
contributes to climate change.
So, why do many people oppose nuclear power?
Uranium and Nuclear Power
 1. Risk of something going wrong with the
nuclear reactor that would release radioactive
particles into the environment. This happened in
1986 in Chernobyl, Ukraine.
High levels of radiation
from radioactive substances
can cause serious diseases
like cancer and even death.
Uranium and Nuclear Power
 Here is an explanation of what happened in
Japan after the tsunami:
 https://www.youtube.com/watch?v=BdbitRlbLDc
Uranium and Nuclear Power
 2. Disposing of uranium is a problem.
 Used uranium is still radioactive and continues to
release radiation and thermal energy for thousands of
years.
 It cannot just be buried in a landfill as the surrounding
rock, soil and water would be contaminated.
 This is a problem that has not yet been resolved, and
the debate continues.