Hydrogen peroxide decomposes to form oxygen gas and water by the following reaction
2 H2O2(aq) 2 H2O(l) + O2(g)
The formation of O2(g) bubbles give us an indication of the reaction rate. The faster the rate at which the bubbles are formed, the faster the reaction rate.
The two tubes below show the results of two reactions. Each contains some hydrogen peroxide, but a small amount of blood (a catalyst for the reaction) has been added to the tube on the right. The faster rate of bubble formation on the right indicates a faster reaction rate. From this we might conclude that the addition of a catalyst to a reaction increases its rate. Of course, we should perform more experiments to increase our confidence in this hypothesis.
2 H2O(l) + O2(g)
