Catalysts-The Glowing Penny (Amy Murphy)

Amy Murphy

Principles Illustrated

• Catalytic Reaction

• cu

  • CH3 – CO - CH3 → CH3COH

  • acetone acetaldehyde

• The high heat of the penny acts as a catalyst for the reaction. In this reaction the acetone is being decomposed into acetaldehyde.

Standards

8th Grade Physical Science Standards

Reactions

5.Chemical reactions are processes in which atoms are rearranged into different combinations of molecules. As a basis for understanding this concept:

a. Students know reactant atoms and molecules interact to form products with different chemical properties.

b. Students know the idea of atoms explains the conservation of matter: In chemical reactions the number of atoms stays the same no matter how they are arranged, so their total mass stays the same.

c. Students know chemical reactions usually liberate heat or absorb heat.

d. Students know physical processes include freezing and boiling, in which a material changes form with no chemical reaction.

e. Students know how to determine whether a solution is acidic, basic, or neutral.

Chemistry Grades Nine through Twelve

Chemical Thermodynamics

7. Energy is exchanged or transformed in all chemical reactions and physical changes of matter. As a basis for understanding this concept:

a. Students know how to describe temperature and heat flow in terms of the motion of molecules (or atoms).

b. Students know chemical processes can either release (exothermic) or absorb (endothermic) thermal energy.

c. Students know energy is released when a material condenses or freezes and is absorbed when a material evaporates or melts.

Questioning Script

Prior knowledge & experience:

Metal things will glow when they are hot.

Pennies are made of metal.

Root question:

What made the penny glow?

What do you think would happen if we were to cover the top of the beaker?

Does the position of the penny above the acetone affect the penny's glowing?

How long will the penny continue to glow?

Will other metals glow when suspended above acetone?

Target response:

The penny is glowing because it is acting as a catalyst in the reaction. Eighth grade students may say that the penny is glowing because there is an chemical reaction. They would also comment that the reaction is exothermic because heat is being given off. The penny will glow as long as there is acetone in the beaker. No other metal will work as well as a penny because copper is such a good conductor of heat.

Common Misconceptions:

All reactions where heat or light is given off require oxygen.

The penny si glowing because of combustion.

Photographs and Movies

References

Liem, T. L., (1987). Invitations to Science Inquiry. Science Inquiry Enterprises, Chino Hills, Ca

JSTOR article about decomposition of acetone (I think...): http://www.jstor.org/stable/94592