WEEK 5: VISCOSITY

A. Materials needed:

  1. Corn starch (flour)
  2. Water
  3. A bowl

B. Instructions:

  1. Put some corn starch into the bowl
  2. Slowly add the water while stirring until the mixture becomes liquidy.
  3. Tap the mixture quickly. It should feel solid, without a splash.
  4. Scoop the mixture and apply pressure to it by squeezing it in your hands. Pass it to a friend and see what happens.

SO IS THE GOO LIQUID OR SOLID?

Different liquids have different viscosities (their resistance to deformation or flow). The more viscous a liquid is, the more slowly it flows; the less viscous it is, the more slowly it flows. For example: Honey is more viscous than Petrol.

 Liquids like water have constant viscosities irrespective of the pressure applied on them. Such liquids are called Newtonian fluids. Other fluids such as the corn-water suspension attain different viscosities and change into liquids or solids depending on the pressure applied. Such fluids are called non-Newtonian fluids.

TAKING IT FURTHER

Repeat this experiment with different liquids such as honey, ketchup or groundnut paste. Is there a difference? Why?