Pin Float

It sits on water.

 

 

 

Category - Solids, Liquids & Gases

Key Idea - Surface Tension

 

Purpose - To see how the molecules of water can pull together and resist breaking

 

 

 

 

 

Pin floating on tissue paper.

 

 

 

 

 

Paper is removed carefully leaving the pin
Nature -  Demonstration
Materials -  Petrie dish or Beaker, water, tissue, clean dry pin, stirring rod
Method - 
  1. three-quarter fill the beaker with water
  2. if your tissue is two-ply, peel the two ply apart and rip one so that it is able to float on top of the water, and float it.
  3. Carefully place the pin on top of the floating tissue
  4. gently use the stirring rod to sink the tissue from under the pin.  The pin will be left floating on the water surface
Safety - Pin pricks?
Explanation - The molecules of water pull together (cohesive force) at the surface.  This creates a weak "skin" that resists breaking to light objects that spread their weight.
Notes - It is important to later sink the pin to make sure that the students understand that the pin is in fact denser (able to sink) and not just floating like wood.

This is the means by which some spiders and water skaters are able to walk across pond surfaces.

It is also possible to do this with a flat razor blade.

This wizard can be easily liked with the Northbound Pin wizard.