Discrepant events are occurrences which defy our understanding of the world by presenting unexpected outcomes. These phenomena are often used in science demonstrations to grab the attention of an audience and engage visual learners, particularly young children. Always encourage students to discuss what will happen before the experiment takes place. Allow them to convince themselves they know what will happen before surprising them with a discrepant event.
THE STEPS ARE
- PREDICT
- OBSERVE
- EXPLAIN
I DEMONSTRATED THE FOLLOWING DISCREPANT EVENTS IN SCHOOL DURING INTERNSHIP
Floating Egg Science Experiment
Materials required:
·
2 Eggs
·
2 Tall Drinking
Glass
·
Salt
·
Water
PROCEDURE:
1. Fill a tall drinking glass about 3/4 full of
water
2. Place the egg into the glass of watch and
watch it sink
3. Fill another tall drinking glass about 3/4
full of water
4. Add 3 Tablespoons of Salt and stir until
combined
5. Place the egg into the glass and watch it
float
REASON:
The egg will sink in regular tap water because the density of
the water is less than the density of the egg itself. Adding salt to the water
increases its density making it more dense than the egg. Therefore the egg will
float in the salt water.
INTERLOCKING OF PAGES OF BOOKS
Materials required: Two books
The trick is set up by the laying of the pages of two books
on top of each other one by one—interleaving them. A volunteer then tries to
pull the phone books apart by force alone, holding on to the books' spines. If
they are set up properly no human, no matter how strong, is capable of pulling
the phone books apart. Even attaching one book to a solid object like a wall
will not provide enough force to separate the pages.
Reason:
The force of friction acting on the pages is a major reason
that pulling the books apart is so difficult. The fact that the pages of two books
are interleaved means that friction as well as weight is preventing them from
being separated. If there are 999 pages in total in contact with each other,
the friction between the pages is equal to 500 times the friction between one
book and another.
FLOATING RICE BOTTLE
Materials required: Bottle, rice,sticks.
Procedure:
Fill plastic bottle up with rice. Stop when the rice is about
an inch from the top.
Put the lid on the bottle and shake it to fluff up the
rice. It should appear nearly full
Add some more rice and continue to tap. You may even
want to use one of the chopsticks to make a few jabs into the rice to pack it
down even better. The important thing is to make both bottle look like
they are full and have the same amount of rice in them.
Gently lift your chopstick. It should “stick” to the
rice well enough to lift the bottle
Reason: When you insert the chopstick into the bottle of packed
rice, it takes up additional space inside of the bottle. Because rice is
not fluid and has great difficulty moving up the neck of the bottle to
compensate for the space that the chopstick takes up, the packed rice has
very little room to move so it tends to press against the sides of the bottle.
The chopstick gets wedged between the rice and the sides of the bottle.
Friction helps to hold the chopstick in the bottle as the bottle is
lifted in air at a time.
BANGING CANS
Materials required
¬
2 empty soft drink cans
¬
24 drinking straws
¬
flat table
¬
extra straws
Procedure: (1) Place the empty cans a few inches apart on a
bed of straws
. (2) Ask the class what they think will happen when you
blow between the cans from above them.
(3) Blow between the two cans from directly above them and
observe what happens. (4) Set the cans up again as in step one and ask the
class what they think will happen when you blow between the cans horizontally
from the level of your flat surface.
(5) Blow horizontally between the cans from the direct level
of the flat surface they are on and observe what happens.
Science behind
It: This demo shows what happens when air pressure is changed between the cans.
When blowing between the cans in step three, the cans rolled away from each
other. This happened because by blowing down between them, you increased the
air pressure between them.
Air has a natural tendency to move from high to low
pressure. Because of this, the cans rolled away from where you blew so that the
high pressure between them could equalize with the lower pressure on the other
side of the cans. However, when you blew between the cans from a horizontal
position in step five, the cans rolled together. This is probably the opposite
of the result that the majority of your class predicted. This occurred because
this time, you lessened the pressure between the cans. As you blew
horizontally, you essentially “cleared out” the air between the cans therefore
creating an area of low pressure.
The higher pressure on the outside of the
cans pushed the cans together towards the area of lower pressure. As the speed
of air increases, the pressure of the air decreases and the faster the air
moves the less pressure it has. The lessening of pressure due to high speed
movement of air is one of the reasons why tornadoes can be very destructive as
objects are thrown into the whirling air by the stronger air pressure around
them.
Students will learn that when there is an opening in an enclosed area such as a bottle or a cup; air can escape and allow room for something else (like the inflated balloon). This example of air pressure relates to our lungs. As we breathe air in, our lungs shrink; and as we breathe out our lungs expand. This is the same principle when your ear pops.
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