The speed of sound is measured in several gases using a pulsed laser to create a micro-spark on a carbon rod and a microphone connected to a digital oscilloscope to measure the time-of-flight of the resulting shockwave over a known distance. These data are used to calculate the heat capacity ratios (C[subscript p]/C[subscript V]) of the gases and the composition of a binary mixture of gases. The application of lasers to the measurement of gas properties provides students with a simple, accurate, and direct, state-of-the-art method for obtaining thermodynamic data. As demonstrated for CCl[subscript 4] in nitrogen gas, the method is capable of determining the vapor pressure of a liquid-vapor equilibrium in another gas. (Contains 3 figures and 2 tables.)