ScienceMakers Toolkit Manual - The History Makers

Learning Objectives
• Experiment with vibrations traveling through air, water, and solids.
• Manipulate variables and observe differences.
• Make inferences based upon the differences observed.
Materials
Per pair:
1 tuning fork
1 wooden board
1 can with balloon stretch across the top
Per demo:
1 32 oz deli cup w/water (see picture at right)
1 tuning fork
Per group of six or eight:
8 oz. deli cup w/salt
Procedures
Vibration Bump
Sounds are produced by vibrations. Vibrations are a form of energy, and this energy is transferred to whatever
is close to it. The molecules of a gas, a liquid or a solid through which the sound vibrations move are
set in motion. These molecules pass the energy to the molecules next to them, which pass the energy along to
the molecules next to them, and so on and so forth, until the energy arrives at the inside of our ear, where it is
changed into electrical impulses and sent to our brain. Our brain then interprets those impulses into the sounds
we recognize.
All along the path that sound travels, the molecules themselves vibrate a lot, but they don’t move very far.
Have a volunteer give the vibrating source sign to one participant and the ear sign to another participant. Now
have all the participants arrange themselves in a line with one sign holder at one end and the other sign holder at
the opposite end. The group will probably need to arrange itself into a semi-circle.
Explain that the people between the vibration source and the ear are molecules. When you ring the bell, the
vibration source is to bump the hip of the air molecule next to it, which bumps the air molecule next to it and so
on down the line until the vibration arrives at the ear. (Caution the older participants to be careful of the younger,
smaller participants.) When the vibration arrives at the ear, that person will hold the sign up high in the air.
There are molecules within the ear that also carry the vibration, but we are not going to go into the various parts
of the ear.
Ring the bell and start the vibration. When the ear sign is up in the air, tell the participants they were great, but
that sound travels a lot faster than they bumped! Repeat the bump more quickly. (Yes, everyone will probably
get a little silly at this point, but the idea of speed will be made.)
Now, there was lots of energy transferred in that activity, but did any of you “molecules” move very far? Not
really, and it’s the same way when molecules transfer energy in the form of sound waves.
Sound travels when molecules pass along vibrations. What are the three states of matter? Can the molecules that
make up these different things all vibrate? Sound has to travel through something - - air, liquid or solid - - and
we call that “something” the sound medium.
While the participants are still standing in their semi-circles, have them stand a little bit closer together. Explain
that they are going to do the vibration bump again. Do they think they will be able to match their speed from
before? Why or why not? Repeat the bell ringing sequence. Did the vibration move as quickly as before?
185
Physics