Tuesday, November 12, 2013

Nursery Rhyme Science: Hickory Dickory Dock

Hickory Dickory Dock,
The mouse ran up the clock.
The clock struck one,
The mouse ran down.
Hickory Dickory Dock.

Activity 1: The Chiming Clock
Can you make a coat hanger sound like a loud, chiming clock?

This is a simple demonstration that helps make the point that sound needs something to travel through and that air is not a very efficient material for that purpose.

You only need a wire coat hanger and a long length of string.

Tie the string onto the hanger, so that the hanger hangs from the middle of the string.

Swing the hanger from the string so that it bumps into something (a table, chair, wall, etc.) and take note of the sound it makes.  It's kind of a short, clang-y sound.  Nothing very dramatic or melodic about it.

Now, wrap one end of the string around one of your index fingers and the other end around the other index finger.

Place your fingers in your ears (gently, there's no need to jam them in).

Swing the hanger so that bumps into something once again and take note of the sound it makes.  Louder and more like a gong or large bell ringing.

In the first trial, the sound made when the hanger hit the object had to travel through the air to reach your ear drum.  A lot of the sound was lost on the way to your ear.  In the second trial, the sound vibrations travel from the hanger through the string and your fingers to your ear.  Much less sound energy is lost in route and it makes an audible difference. 

Tuesday, November 5, 2013

Nursery Rhyme Science: Row, Row, Row your boat

Row, row, row your boat
Gently down the stream.
Merrily, merrily, merrily, merrily,
Life is but a dream.

Activity 1: Soap Boats
Show your students two bars of soap - one bar of Ivory soap and a bar of any other brand of soap.  Ask them which bar they think would make the better boat and why.  

Put the bars of soap in a pan of water (a clear tub is good, so everyone can see easily) and observe.  

After seeing what happened (Ivory soap floats, all other brands sink), which soap do they think would make the better boat now? 

Ivory whips more air into their soap than other brands, so it is less dense than water and will float.  
You can even make a little mast and sail with a coffee stirrer and piece of fun foam :) 
(My boys came home from preschool with an Ivory soap boat each Columbus Day!)

Activity 2: Boat Races

Cut out a boat shape from an index card or piece of thin cardboard.

Cut a small notch out of the back of the boat.

Float the boat in a tub of water.  What happens?  Not much!

Now, place a small sliver of soap in the notch and watch.  What happens?  The boat moves across the tub!

Without soap, the water pulls on the boat from all directions, resulting in little to no movement.  When the soap is added, it reduces the pull of the water at the back of the boat.  The pull at the front of the boat remains  strong and you see movement. 

Students can experiment with boat shape to find the fastest (and straightest) racer!

Because the soap reduces the water's surface tension, the water in the tub will need to be dumped out and replaced often.