Hot or cold? Chemical Reactions

Through the process of a chemical reaction, energy (in the form of heat) can sometimes either be given off or taken in. The technical terms for these types of reactions are exothermic (giving off heat) and endothermic (taking in heat). Most of the time when we think of heat given off, we think of fire or an explosion which can be a very spectacular reaction. On the other hand, when we think of heat taken in, we think of something getting cold, very slowly.

In this experiment, we tested the hypothesis that exothermic reactions are big and spectacular and endothermic reactions are relatively boring. The very quick and spectacular reaction between vinegar (Acetic Acid – CH3COOH) and baking soda (Sodium Bicarbonate – NaHCO3) produced Sodium Acetate (C2H3NaO2) and Carbon Dioxide (CO2). In doing this, the reaction took in heat from the surrounding atmosphere, making it endothermic. By producing CO2, it also inflated the sealed freezer bag.

In the second half of the experiment, soaking the steel wool in vinegar (Acetic Acid) actually helped dissolve the protective coating on the steel wool allowing the Iron (Fe) in the steel wool to be exposed to Oxygen (O2) and Water (H2O) in the atmosphere. When these three chemicals combine, Iron (III) Oxide (Fe2O3)or “rust” will be formed. In the chemical reaction of iron rusting, heat will be given off, making this an exothermic reaction. But the reaction is not nearly as spectacular as the vinegar and baking soda endothermic reaction.