Rusting steel wool and other heat releasing reactions.
We can start a fire with a battery and some steel wool. It is actually a rusting reaction that occurs quickly and gives off a great deal of heat.
Watch the video on the right. Steel wool is firstly heated with an electric current delivered via a 9V battery. As can be seen from the video, rusting generates its own heat, in other words it is an exothermic reaction, and in the process produces iron oxide or rust.
Cars made of iron rust slowly over time. The heat given out during the rusting reaction can not be felt as the rusting process occurs over a long time and at a slow rate. Speed the reaction up, however, and the heat can actually be harnessed.
Consider the video above of the steel wool rusting.
1) What is the mass change of the steel wool?
2) How do you explain the gain in mass of the steel wool?
The thermite reaction shown on the right, in time lapse, is actually a very quick rusting reaction. The metal being rusted, however, is not iron but aluminium. Notice the amount of heat generated.
Even the addition of water can sometimes cause a great deal of heat to be released. Strange that water can cause the release of so much heat as to cause a serious burn but the video on the right clearly shows the release of energy when water is added to a dry, cold, chemical (anhydrous copper sulfate).
Sugar also undergoes an exothermic chemical reaction when it burns in oxygen. The video on the right shows the amount of energy released from a teaspoon of sugar.
