Electrical Corn Starch (Andrew Salg)
Author
Andrew Salg
Principle(s) Illustrated
Non-Newtonian Fluids
Molecular Interaction
Standards
HS PS1-3 Plan and conduct an investigation to gather evidence to compare the structure of substances at the bulk scale to infer the strength of electrical forces between particles.
HS PS2-6 Communicate scientific and technical information about why the molecular-level structure is important in the functioning of designed materials.
Questioning Script
Materials Needed:
1/2 a cup of cornstarch
1/2 a cup of vegetable oil
A bowl or measuring cup
1 Balloon
A large spoon
Something to conduct static electricity (e.g. hair, clothing, pieces of wool)
Prior knowledge & experience:
The students should already know electrons as a type of molecule found in
elements and compounds. The students should also already know that
balloons can cause static electricity. The students must also have the
knowledge to be able to observe closely to notice the interaction between the
balloon and the corn starch.
Root question:
What will happen to the corn starch when the balloon is brought close the
corn starch in the spoon?
Target response:
The corn starch will jump up in the air trying to touch the balloon. This is
because of static electricity built up in the balloon, and the neutral particles in
corn starch will be drawn to the negative charge of the balloon. The reason is
because corn starch is a non-Newtonian fluid because it does not know
whether to act as a solid or a liquid, so it will not act like a traditional
liquid according to Newton's laws of liquids. The balloon and the spoon with
the corn starch must be close or else it will not work. This can not be done
with a larger amount of corn starch because the neutral charge will be too
great to overcome. However, if a larger object with a charge came by, it may
be possible, but it will not be that discrepant.
Common Misconceptions:
The fluid will do nothing is the most common misconception that students
have. Others think that their will be a spark in some cases because of the
static electricity.