CAPRICORN DISTRCITPHYSICAL SCIENCES PRACTICAL WORKSHEET 2013

GRAGE 11 PRESCRIBED EXPERIMENT 2

Name of school:_________________________________________

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

ApparatusYou 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

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Due date: 17 May 2013

Raw mark

Converted narkLearner mark

permanent 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.

Results

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).

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Substance Liquid level after 1 min

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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20 ml methylated spirits

20 ml nail polish remover20 ml ethanol

20 ml water

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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).

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Substance Shape of meniscus

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)

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Part 3: The effects of intermolecular forces - solubility

Aim

To investigate solubility and to determine the relation between solubility and intermolecular forces

Apparatus

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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 paperMethod

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.

ResultsRecord 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.

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Substance Water

Chloroform

Ethanol

Sodium chloride      

Potassium permanganate

     

Iodine      

Table 3 (1 mark for each recording)Discussion and Conclusion

What conclusion can be drawn from your observations (results)?(3)

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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.

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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.

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.

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Discussion and conclusion

What conclusion can be drawn from your observations (results)?(3)

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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.

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Hot plate

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.

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.

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Substance Distance travelled up tube

Water  

Oil  

Nail polish remover

 

Methylated spirits  

Table 4 (1 mark for each recording)

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Discussion and conclusion

What conclusion can be drawn from your observations (results)? (3)

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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.

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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)

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)

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Which oil has the weakest overall intermolecular forces?...................... (1)

Discussion and Conclusion

What conclusion can be drawn from your observations (results)?(2)

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