The Domino Effect :: Science Saturday - Eva Varga

Frequently, the munchkins will entertain themselves watching videos on YouTube … Buddy searches “Lego Trains” or “HO Trains” while Sweetie will search “Polymer Clay” or “Paper Crafts”.  I was surprised to discover that what caught their attention this past week were Dominoes.  They spent hours watching videos and then trying to set up similarly complicated patterns.  They even used my iPhone to record their own videos and take photos of their designs before they were made to fall.

All the while they played investigated the properties of dominoes and experimented, I kept thinking to myself,  “We should really be doing schoolwork.  We have quite a list of tasks that are due next week.”  Then inspiration struck … “What they are doing is science!  So I ran into the dining room where they had set up their testing space.  “I have a challenge for you both,” I said as I gave them a stopwatch and a meter stick.    “How does the distance apart affect how fast dominoes fall? You might try and find out … maybe at 2cm apart and at 4cm apart.”  I then walked away. 

They had some experience recording their results in the past with other experiments so not wanting to interfere – or take over as I have a tendency to do – I left this one up to them.  Upon completion of their test, we sat down with their results table and discussed how it all meant.   

Purpose: This investigation will determine whether the speed of sound is affected as it travels through a solid, liquid, or gas.  In this experiment, think of the dominoes as molecules that make up a solid, liquid, or gas.  Sound travels in waves or moving molecules.





Materials
box of dominoes
smooth surface
ruler or yardstick
stopwatch or a watch with a second hand


Procedure

1. Line up dominoes approximately 2 cm apart, stretched out over a 100-cm length.
2. Measure the time it takes for all the dominoes to fall. Be sure to start the timer just as you knock over the first and stop it just as the last domino hits the surface.
3. Record the amount of time it took for all the dominoes to fall.
4. Line up the dominoes again, this time 4 cm apart, stretched over a 100-cm length.
5. Predict the amount of time it will take the dominoes to fall and record your prediction.
6. Measure the time it takes for all the dominoes to fall. Be sure to start the timer just as you knock over the first and stop it just as the last domino hits the surface.
7. Record the amount of time it took for all dominoes to fall. How close was your prediction to the actual time?
8. Set up both lines of dominoes so that they each stretch to 100 cm, but one line should be placed 2 cm apart and the other line 4 cm apart. Lines should be parallel to each other.
9. Knock the first domino of each line over at the same time. What do you notice?
10. Answer the following questions:
    • Which dominoes traveled faster, the ones 2 cm or the ones 4 cm apart?
    • Think of dominoes as molecules. Which line of dominoes (molecules) represented a solid (2 cm or 4 cm)? Which line represented a liquid (2 cm or 4 cm)? Think about the three states of matter: How do the molecules behave in a solid, liquid, and gas?
    • How would you explain the results of your findings to someone else by using these words: chain reaction, wave, solid, liquid, and traveling ?
    • How far apart would you place the dominoes if you wanted to investigate a wave
      moving through gas (like air)? Base this decision on the two measurements already given.
    • Predict the amount of time (another hypothesis!) it would take for the dominoes
      representing gas to fall through a 100-cm line.

What’s Happening?
Matter consists of tiny particles called molecules, and these molecules are always moving around and bumping into each other. They react as the dominoes did when the first one fell into the second. Sound energy in the form of vibration is transferred from one molecule to another. Energy is transferred from one domino to another as they fall to the table. In the first activity, the dominoes are placed closer together, and the sound travels faster through the particles, much as in a solid (molecules are close together). In the second activity, the dominoes are placed farther apart and the sound travels slower through the particles, much as they do in a liquid (molecules are farther apart than in a solid).