Kinetics is an extremely important concept for introductory chemistry courses. While it is critical that students are able to determine whether or not a chemical reaction will occur from a thermodynamics perspective, they should also be able to predict and determine information on the rate of the reaction. Kinetics experiments in introductory chemistry courses primarily concentrate on the determination of the concentrations of reactants or products, the order of the reaction with respect to individual species, or the overall reaction order. Knowledge of reaction order can help one ascertain the reaction mechanism. Reaction kinetics experiments in introductory chemistry courses are most often studied either using spectroscopy by observing the change in the visible color of a solution as one species is produced or consumed or by measuring pressure changes in the production or consumption of gas phase species (1-6). To further help students understand the concept of orders of reaction, a recent publication in this Journal suggests some useful processes simulating reactions occurring under different orders of reaction (7).The experiment presented here analyzes the change in gas pressure to examine the kinetics of the iron in steel wool reacting with molecular oxygen as represented in the equation:Birk et al. first discussed the possibility of studying the kinetics of this reaction (8). This experimental design has long been used to determine the percentage of oxygen in the air. Typically, a pretreated piece of steel wool is placed into a test tube that is then inverted into a beaker of water. As the iron in the steel wool reacts with the molecular oxygen, water rises into the test tube to compensate for the decrease in pressure.In this experiment, a Vernier oxygen gas sensor is placed in the mouth of a test tube to measure the decrease in oxygen concentration as it reacts with the steel wool.The general expression for the rate of change in concentration of oxygen with time isGraphing the integrated rate law expressions for the values of x equaling zero, one, and two was used to determine the order of the reaction with respect to oxygen. While there are cases when x is a fractional value, for example, 0.5 or 1.5, those are for more complex systems than we choose to discuss in our introductory chemistry course. The rate expressions and the integrated forms of the expressions can be seen in Table 1. In the expressions the initial concentration of oxygen and the concentrations at various times, are designated with the superscripts i and t, respectively. The rate constant for the expression is given as k.The oxygen gas sensor is designed for measuring gaseous, not aqueous, oxygen concentration. In the sensor's electrochemical cell, the partial pressure of oxygen is measured and the corresponding voltage is converted to an equivalent concentration of oxygen in units of the percent of oxygen. Therefore, the percent of oxygen was substituted for the molar concentration in the integrated rate expressions and designated with s...