TITLE: SLIPPERY SUBSTANCES - LUBRICANTS
AUTHOR: Rebecca Sexson, Anasazi Elementary School,
Scottsdale, AZ
GRADE LEVEL: Appropriate for grades 3-4.
OVERVIEW: Slippery Substances are called lubricants.
They are very important in modern technology. Cars,
trucks, airplanes, and machines all have parts that rub
against one another. These parts would heat up, wear
down, and stop working if we did not have lubricants.
Lubricants reduce the amount of friction between 2
surfaces that move against each other.
OBJECTIVE(s): Students will be able to:
1. Demonstrate which lubricant is best
(slipperiest), of those used for the experiment.
2. Explain how a lubricant works.
3. Identify objects that need lubricants to work
well.
RESOURCES/MATERIALS:
Teacher Materials = 4 envelopes unflavored gelatin, 8
inch square baking pan, mixing bowl, liquid dish
detergent, vegetable oil, 2 bowls, clock or watch with
a second hand, a knife, measuring cup
Student Materials = pencil, science journals
ACTIVITIES AND PROCEDURES:
1. Dissolve 4 envelopes of gelatin in a bowl of 2
cups of hot tap water.
2. Coat the inside of a 9 x 12 inch pan with
vegetable oil. Pour the gelatin mixture into the
pan and refrigerate until firm (about 3 to 4
hours).
3. Cut the gelatin into cubes about 1x1x1 inch, with
a knife. You should have about 64 cubes.
4. Place 15 cubes into a bowl. Place the second bowl
about 6 inches away from the cube bowl.
5. See how many cubes can be transferred to the other
bowl in 15 seconds by using your thumb and index
finger one at a time. (Don't squeeze!)
CAUTION: Children should be cautioned not to eat
the gelatin cubes after they have been handled or
after they are covered with lubricant.
6. Return all the cubes to the first bow. Pour 1/4
cup dish detergent over the cubes. Gently mix the
detergent and the cubes so that the cubes are
well-coated.
7. Use the same method as before to transfer as many
cubes as possible in 15 seconds.
8. Throw away the cubes and detergent and wash and
dry both bowls. Put about 15 new cubes into one
bowl and; pour 1/4 cup water over the cubes, again
making sure the cubes are thoroughly coated. See
how many cubes you can transfer in 15 seconds.
9. Throw away the cubes and water. Put about 15 new
cubes into one bowl. Pour 1/4 cup of vegetable
oil over the cubes. Make sure they are well
coated. See how many cubes you can transfer in 15
seconds.
10. Analyze your findings. With which liquid were you
able to transfer the most cubes? With which
liquid were you able to transfer the fewest cubes?
Which was the best lubricant (the slipperiest)?
Which was the worst?
TYING IT ALL TOGETHER: Students should now understand
vocabulary words such as lubricant, friction, gravity,
force, momentum, and machine. This is an ideal
activity to follow a study of simple machines. Mr.
Gumpy's Motorcar, written by John Burningham, is a good
introduction and motivator. Students should be able to
list objects that have working parts that would need
lubricants to protect their parts, such as cars,
trucks, bicycles, etc.
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