Chapter Review 9
1. The function of the filter used in each situation is:
a) A nurse wears a surgical mask while examining a patient’s mouth to prevent germs,
vapours, and odors from entering the nurse’s nose.
b) The air filter in a vacuum cleaner has to be changed every so often in order to collect
tiny, solid particles from the air.
c) An auto mechanic changes the gasoline filter during a maintenance checkup in order
to collect tiny, solid particles (impurities) from the gasoline.
d) An archeologist passes soil through a sieve while looking for ancient pottery
fragments. A filter used here will separate rock material from pottery fragments.
e) A hanging basket for plants has small holes in the bottom through which water can
pass. The holes let excess water out of the basket so roots don’t become water
logged.
f) Some people wear a mask made of mesh that covers their whole head when they
walk through an area with lots of mosquitoes. The mask prevents mosquitoes from
gaining access to the face.
2. Mechanical sorting can’t be used to recover any part of a homogeneous mixture
because the parts of such a mixture are too small to be filtered or otherwise
mechanically separated.
3. Evaporation could be used to recover some parts of a heterogeneous mixture because
any parts of the mixture that were dissolved or suspended in the liquid component
would remain behind.
4. The membrane (skin-like covering) of a cell prevents most substances from entering the
cell and most substances from leaving it. Only water particles and some salts are able to
pass unassisted through the cell membrane. The cell membrane is a type of filter
because (like other filters) it permits some substances to pass through and not others.
5. Magnetism and sorting by hand are examples of mechanical sorting because the parts of
the mixture can be separated by physical manipulation fairly easily.
6. In a restaurant, several kilograms of dried rice are poured into a large pot filled with
water. Soon, small specks of dust and dirt are visible on the surface of the water. The
rice is on the bottom of the pot, below the water’s surface.
a) The type of mechanical sorting that is identified here is flotation.
b) The property on which this separating technique depends and why it works is;
Flotation depends on the property of density. The density of rice in water is greater
than the density of the dust and dirt specks in water, so the rice sinks to the bottom
of the pot and the other materials float. Note: the results could be different for a
different type of liquid.
7. The particle theory of matter can explain why distillation can separate pure water from
a sample of tap water because tap water is a solution that is made up of water particles
and the particles of various other solutes. Distillation cause the water particles to move
faster and farther apart with the addition of heat, leading to a change of state from
liquid to gas. As the particles of gaseous water are cooled, the particles move more
slowly and their spacing decreases; that is, the water condenses. The resulting liquid is
pure water, separated from the solutes that once were dissolved in it.
8. People who get lots of unwanted e-mail, called spam, may install a computer program
called a spam filter. Like all filters, a spam filter works by trapping some things (e-mails)
and allowing others to pass through. Two essential differences between a spam filter
and an actual filter are a) e-mails are not real (they are virtual) and b) spam filters use
criteria other than holes and particle size to perform their function.
9. You have a mixture of clean sand and pure table sugar. You can get pure sugar from this
mixture by: you could add water to dissolve the sugar, filter the mixture to remove the
sand, and then use either distillation or evaporation to recover the sugar. Equipment
needed for these processes would include water, filter paper, a source of heat, and
containers to hold the substances/mixtures at different steps of the process.
10. The term volatile is used to describe a substance that changes state to become a gas at
a low temperature. Volatility from lowest to highest:
i)
ii)
iii)
iv)
v)
Asphalt and tar
Greases
Lubricating oils
Diesel oil
Kerosene
vi)
vii)
viii)
Jet fuel
Gasoline
Propane
11. You are thirsty and ask for a glass of apple juice. You are given two glasses of apple
juice. One appears to be homogeneous. The other is heterogeneous, because you can
see bits of sediment-like material at the bottom of the glass.
a) The one that appears homogeneous is the solution
b) What you could do to make the other mixture into a solution is the mixture could be
filtered to obtain a solution of apple juice.
12. Imagine that you place the following materials into a large container: 100mL of water,
100mL of vegetable oil, a handful of marbles, a tablespoon of gravel, a handful of puffed
wheat, and a tablespoon of iron filings. The methods that could be used to remove as
many of the parts of this mixture as possible are: The marbles and gravel can be
removed by filtration. (The marbles also could be picked out by hand). The iron filings
can be removed from the whole mixture or a filtered mixture by magnetism. The puffed
wheat will float and can be removed by hand. The water can be removed by distillation
(or evaporation, if recovery is not desired). The vegetable oil will remain. Vegetable oil
can be removed from the water by skimming after freezing if desired.
13. You might separate sugar from a solution of vinegar and sugar by evaporation or
distillation.
14. “Campfire” coffee is made by boiling ground coffee beans in water over a campfire or a
special butane burner. Then the coffee mixture may be poured through a strainer.
Other methods of making fresh coffee at home also involve filtering.
a) Filtration allows the liquid coffee-water mixture to be separated from the grounds of
coffee once the water has dissolved/extracted the various desired substances from
the grounds.
b) The filter does its job by having holes that are small enough to trap the size of the
coffee grounds.