APPLICATION: tow lines; tug of war

SUBJECT AREA: Chemistry, General Science

CONCEPTS COVERED: Spontaneous Combustion

MATERIALS:

1. Sodium peroxide - Na2O2

2. Finely chopped tissue paper, or sawdust, or starch.

3. A small chip of ice.

PROCEDURE:

1. Before doing anything, show students a piece of tissue paper and ask: Would I be able to burn this piece of tissue paper with ice?"

2. Tear or cut tissue paper into very fine pieces and place them in a heap on an asbestos/ tile plate, and build it up to a cone which is about 5 cm high in the center.

3. On top of the cone, place a half teaspoon of sodium peroxide.

4. Now show the students the small chip of ice and put it on top of the heap stand back and observe.

QUESTIONS:

1. What reaction took place? What made the paper burn?

2. What does the burning process need in terms of chemicals?

3. What was the function of the sodium peroxide?

4. Why was it necessary to divide the paper into such small pieces?

5. What else besides paper could we use to replace the paper?

6. What is the reaction between sodium peroxide and water.

7. Is this reaction exothermic or endothermic?

8. Would regular writing paper work better or worse than tissue paper? Why?

RATIONALE:

The chip of ice at room temperature will melt and turn into water. The reaction between water and sodium peroxide is as follows:

Na2O2 + H2O ----> 2NaOH + On + energy(heat)

The oxygen released from the above reaction is in status nacendi, this means that it is in atomic form, and thus very reactive. The very reactive oxygen immediately attacks the combustible paper and sets it into flames. By slicing the paper into fine pieces, we actually decrease the kindling temperature or the activation energy needed to drive the reaction. In place of the paper we can use fine sugar, fine coal powder, or any other highly combustible material. The reaction is very exothermic, and the released heat is enough to further decompose more of the sodium peroxide, which releases more active oxygen.

APPLICATION:

Automobiles, engines, Human body (sugars)

Na2O2 + H2O ----> 2NaOH + On + energy(heat)

The oxygen released from the above reaction is in status nacendi, this means that it is in atomic form, and thus very reactive. The very reactive oxygen immediately attacks the combustible paper and sets it into flames. By slicing the paper into fine pieces, we actually decrease the kindling temperature or the activation energy needed to drive the reaction.

In place of the paper we can use fine sugar, fine coal powder, or any other highly combustible material. The reaction is very exothermic, and the released heat is enough to further decompose more of the sodium peroxide, which releases more active oxygen.

REFERENCES: Liem, Tik, L. Invitations to Science Inquiry. 1992. Science inquiry enterprises; Chino Hills, California.