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!






Why?
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.

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