There are many concepts explored in "Enthalpy Vaporization of Water". First of all, the purpose of this lab was to determine the pressure of water vapor at different temperatures and measure the molar heat of vaporization of water using the Clausias Clapeyron equation. The first of the many concepts represented in this laboratory is the ideal gas law. The ideal gas law is used to obtain the number of moles of air trapped in the 10 ml graduated cylinder. Once we cooled the system so that the water vapor is extremely minute, we determined the number of moles of air using the ideal gas law. The number of moles of air is equal to the pressure (in atm) times the volume divided by the constant times the temperature. One might assume that when water is heated to 80 degrees, the number of air molecules in the air bubble would decrease, but in reality it remains constant. This is due to the fact that there is no air entering or exiting the cylinder. As the temperature approaches 80 degrees, the number of air molecules remains the same but water vapor increases. And the bubble expands to keep the pressure at the same level. The ideal gas law was also used to calculate the partial pressure of air in the gas mixture. This is obtained by the number of moles multiplied by the constant and the constant and all divided by the volume. Dalton's partial pressure law is then used. The gas mixture in the graduated cylinder was filled with two things: water vapor and air. Using Dalton's law, it can be concluded that the total pressure is equal to the air pressure and water vapor pressure added together. This is an endothermic reaction, meaning it absorbs heat and when a reaction gains heat, it is represented...... middle of paper ......inty between 1.0% (0.1/10.00 *100) and 2.13 % in the measured volume and 0.1/4.70*100). We also used a digital thermometer that allowed us to take temperature readings from five degrees Celsius to eighty degrees Celsius. Since the digital thermometer has an absolute accuracy of plus or minus one degree Celsius, it provides a percent uncertainty between 0.125% (0.1/5.00 * 100) and 0.2% (0.1/80.0 * 100). One of the difficulties we encountered during the laboratory was reading the inverted graduated cylinder. To account for the reverse meniscus, we subtracted 0.2 ml from all volumetric measurements. The volumetric uncertainty is the most important in determining the accuracy of this experiment since we constantly monitor the volume throughout the laboratory. It is also the factor that provides the highest percentage of uncertainty among all the tools used.