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grade-11-experiment-2-of-2013-effects-on-intermolecular-forces-1

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Due date: 17 May 2013
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CAPRICORN DISTRCIT
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PHYSICAL SCIENCES PRACTICAL WORKSHEET 2013
GRAGE 11 PRESCRIBED EXPERIMENT 2
Name of school:_________________________________________
30
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Learner mark
Name of Learner:________________________________________
Topic: The effects of intermolecular forces
The following five experiments investigate the effect of various physical
properties (evaporation, surface tension, solubility, boiling point and capillarity)
of substances and determine how these properties relate to intermolecular
forces. Each experiment will look at a different property.
Part 1: The effects of intermolecular forces - Evaporation
Aim
To investigate evaporation and to determine the relation between evaporation
and intermolecular forces
Apparatus
You will need the following items for this experiment:

ethanol, water, nail polish remover (acetone), methylated spirits

evaporating dishes (or shallow basins)
Method
1.
Place 20 ml of each substance given in separate evaporating dishes.
2.
Carefully move each dish to a warm (sunny) spot.
3.
Mark the level of liquid in each dish using a permanent marker. Make
several marks at different positions around the dish. If the permanent
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marker is leaving a smudge rather than a noticeable mark, carefully wipe
the side of the dish and try again.
4.
Observe each dish every minute and note which liquid evaporates fastest.
20 ml ethanol
Results
20 ml nail polish remover
20 ml water
20 ml methylated spirits
Record your results in the table below. You do not need to measure the level of
the liquid, but rather just write how much the level had dropped (e.g. for water
you might write did not notice any decrease in the level or for ethanol you might
write almost all the liquid had evaporated).
Substance
Liquid level after
1 min
(12)
2
min
3
min
4
min
5
min
Ethanol
Water
Nail polish remover
Methylated spirits
Table 1
(3 marks for each row recordings)
Discussion and conclusion
What conclusion can be drawn from your observations (results)?
(3)
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
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Part 2: The effects of intermolecular forces – Surface tension
Aim
To investigate surface tension and to determine the relation between surface
tension and intermolecular forces
Apparatus
You will need the following items for this experiment:

water, cooking oil (sunflower oil), glycerin, nail polish remover (acetone),
methylated spirits


small glass beakers or glass measuring cylinders
small piece of glass or clear plastic (about 5 cm by 5 cm.)
Method
1.
Place about 50 ml of each substance given in separate small beakers or
measuring cylinders.
2.
Observe the shape of the meniscus. (This is the level of the liquid). Note
what happens at the edges where the liquid touches the glass. (You can
place a few drops of food colouring in each substance to help you see the
meniscus.)
3.
Now place a drop of the substance on a small piece of glass. Observe the
shape of the drop.
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Results
Record your results in the table below. You just need to give a qualitative result
(in other words what you see in the experiment).
Substance
Shape of meniscus
(10)
Shape of droplet
Water
Oil
Glycerine
Nail polish remover
Methylated spirits
Table 2
(1 mark for each recordings)
Discussion and conclusion
What conclusion can be drawn from your observations (results)?
(3)
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
Part 3: The effects of intermolecular forces - solubility
Aim
To investigate solubility and to determine the relation between solubility and
intermolecular forces
Apparatus
You will need the following items for this experiment:

Solids: sodium chloride (table salt), iodine, potassium permanganate
Solvents: water, ethanol, chloroform

9 beakers or test-tubes

3 A4 sheets of paper

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Method
1.
Place about 20 ml of each solvent given in separate beakers. Place this set
on a piece of paper labelled “sodium chloride”.
2.
Repeat this step twice. The second set is for potassium permanganate (so
your piece of paper will say “potassium permanganate”) and the third set
is for iodine (so your piece of paper will say “iodine”). You should now have
nine beakers in total.
3.
Into the first set, add about 2 g of sodium chloride.
4.
Into the second set, add about 2 g of potassium permanganate.
5.
Into the third set, add about 2 g of iodine.
6.
Observe how much of each substance dissolves in the solvent.
Results
Record your results in the table below. If you observe only a small amount of
the solid dissolving then write that very little solid dissolved. If all the entire
solid dissolves then write that all the entire solid dissolved.
Substance
Water
Chloroform
(9)
Ethanol
Sodium chloride
Potassium permanganate
Iodine
Table 3
(1 mark for each recording)
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Discussion and Conclusion
What conclusion can be drawn from your observations (results)?
(3)
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
Part 4: The effects of intermolecular forces – Boiling point
Aim
To investigate boiling point and to determine the relation between boiling point
and intermolecular forces
Apparatus
You will need the following items for this experiment:
water, cooking oil (sunflower oil), Glycerine, nail polish remover,

methylated spirits

test-tubes and a beaker

hot plate
Warning:
Methylated spirits and nail polish remover are highly flammable. They will easily
catch fire if left near an open flame. For this reason they must be heated in a
water bath. This experiment MUST be performed in a well ventilated room.
Method
1.
Place about 20 ml of each substance given in separate test-tubes.
2.
Half-fill the beaker with water and place on the hot plate.
3.
Place the test-tubes in the beaker.
4.
Observe how long each substance takes to boil. As soon as a substance
boils, remove it from the water bath.
Hot plate
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Results
Write down the order in which the substances boiled, starting with the
substance that boiled first and ending with the substance that boiled last.
(4)
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
Discussion and conclusion
What conclusion can be drawn from your observations (results)?
(3)
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
Part 5: The effects of intermolecular forces - Capillarity
Aim
To investigate capillarity (how far up a tube a liquid rises or how far down a
liquid falls) and to determine the relation between capillarity and intermolecular
forces.
Apparatus
You will need the following items for this experiment:

water, cooking oil (sunflower oil), nail polish remover, methylated spirits

large shallow dish, narrow glass tube (with one end closed)
Method
1.
Place about 20 ml of water in the shallow dish.
2.
Hold the narrow tube just above the level of the water in the dish.
3.
Observe how far up the tube the water travels.
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4.
Repeat for the other three substances, remembering to wash and dry the
dish and tube well between each one.
Results
Record your results in the table below. You do not need to measure how far up
the tube the substance travels but rather say if it only travelled a short
distance or a long distance.
Substance
(4)
Distance travelled up tube
Water
Oil
Nail polish remover
Methylated spirits
Table 4
(1 mark for each recording)
Discussion and conclusion
What conclusion can be drawn from your observations (results)?
(3)
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
Page | 8
Viscosity
Viscosity is the resistance to flow of a liquid. Compare how easy it is to pour
water and syrup or honey. The water flows much faster than the syrup or honey.
You can see this if you take a cylinder filled with water and a cylinder filled with
glycerin. Drop a small metal ball into each cylinder and note how easy it is for
the ball to fall to the bottom. In the glycerin the ball falls slowly, while in the
water it falls faster.
Substances with stronger intermolecular forces are more viscous than
substances with weaker intermolecular forces.
Activity 1: Machine and motor oils
You are given the following information about engine oils.
Oil
Use
Other info
SAE 30 monograde
Engines
Low viscosity
SAE 50 monograde
Engines
High viscosity
SAE 15W-40 multigrade
Engines
Medium viscosity
SAE 0W-40 multigrade
Engines
Medium viscosity
Table 6
(Data from shell.com)
Page | 9
Multigrade oils can be used even in cold weather since they remain fluid.
(The first number is the rating for winter weather and the W shows that this is
the rating in winter. The second number is the viscosity rating in summer).
Monograde oils are given their viscosity rating at 100°C. The viscosity is an
indication of how well the oil flows. The more viscous an oil the larger the
molecules that are in the oil

Which oil has the longest molecules?.....................................................
(1)

Which oil has the shortest molecules?.................................................
(1)

Which oil has the strongest overall intermolecular forces?.................... (1)

Which oil has the weakest overall intermolecular forces?...................... (1)
Discussion and Conclusion
What conclusion can be drawn from your observations (results)?
(2)
_______________________________________________________________________________
_______________________________________________________________________________
_______________________________________________________________________________
Page | 10
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