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OBJECTIVES:
Cars, airplanes, bicycles
and other machines all have moving parts that rub against each other.
These parts will wear out, heat up, and fail
to work without the aid of lubricants to reduce the friction
between surfaces. There are different types of lubricants. Some lubricants can only be used with certain materials.
In this experiment you will try and move
gelatin cubes with and without a lubricant. How many can you move?
STEPS TO FOLLOW:
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Make the gelatin cubes at least 3-4 hours before the
demonstration.
Mix 4-3 oz. packages of gelatin with 2 cups of hot tap water in one
of the bowls.
Pour into a 9" X 9" pan coated with vegetable oil or vegetable spray.
Refrigerate for 3-4 hours. Cut into 64 cubes approximately 1" X 1" X 1".
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Place 15 cubes in one bowl. Place the second bowl 6 inches away.
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Have one student volunteer to transfer the cubes one at a time
to the second bowl with their thumb and index finger.
(No squeezing!)
On the count of 3, the volunteer should begin
transferring cubes. Use the stop watch to time the number of
cubes transferred in 15 seconds. Record that number on
your worksheet. Did
the cubes stick to the first bowl?
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MATERIALS:
4-3oz. Packages of Gelatin Mix
2 Medium Sized Bowls
Spoon
Butter Knife
Stop Watch
Vegetable Spray or 1 Teaspoon Vegetable Oil
1/4 Measuring Cup
1/4 Cup Vegetable Oil
1/4 Cup Liquid Dish Soap
1/4 Cup Water
(Note: This demonstration can be a class or team activity.
If using student teams duplicate these supplies for each team.)
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As you add the different lubricants in Steps 6-8 ask yourself these questions:
Do the cubes stick to the first bowl?
Are the cubes easier to grab?
Are the cubes easier to move?
Does the lubricant coat the cube or start to dissolve the cube?
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Put all the cubes back in the first bowl. Pour 1/4 cup of
the liquid detergent over
the cubes and mix so all the cubes are well coated.
Repeat Step 4. Record how many cubes were transferred
on your worksheet.
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Throw away the cubes and detergent and wash and dry both bowls. Put 15 new
cubes into one bowl and pour 1/4 cup of water
over them. Again, mix to make sure the cubes are well coated. Repeat Step
4. Record how many
cubes were transferred on your worksheet.
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Throw out the cubes and water and wash and dry both
bowls. Put 15 new cubes into one bowl and pour 1/4
cup of vegetable oil over them. Make sure the cubes
are well coated. Repeat Step 4. Record how many cubes were transferred
on your worksheet.
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Complete the questions on the worksheet and plot your results.
What conclusions can you make from the results? Why do you think
this experiment is called "Slime"?!!!!!
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