1/13-1/17

            This week in class we did a comprehensive review of all things gasses and did some demonstrations with liquid nitrogen. We did a lot of whiteboarding of problems involving ideal gases and real gases. The difference between the two can be taken into account by properties of gases and IMF’s and are seen in effect with Van der Waal’s equation.

            The bulk of the week was spent working on problems from the Gases I and Gases II worksheets. The Gases I worksheet had a lot to do with problems that involved the ideal gas equation. This is PV=nRT. We can manipulate this equation to solve for any one of the four variables that can affect gases. An ideal gas is not something we actually see in real action but is just a hypothetical gas whose pressure, volume, and temperature can be described by this equation.  We also discussed a little bit the effects of STP and what it is exactly. STP is the standard temperature and pressure conditions of gases at 0° C and 1 atm. The volume of STP conditions is 22.4 L. We also faced some problems where P, V, and T all changed for a constant number of moles. When this happens we can set up an equation where P₁V₁/T₁=P₂V₂/T₂. This equation is very helpful for finding a final variable if we know all the initial variable’s and two of the final variables or vice versa for finding an initial variable.

            We also looked at some further applications of the ideal gas law. This involved density and molar mass. Since D=M/V we can substitute in variables for volume if we need to do so. We also know that molar mass is equal to mass per one mole of substance. We can use this knowledge to rework our ideal gas equation to solve for molar mass and density of gases.

            We also touched on effusion and diffusion. Effusion is the escape of molecules through a tiny hole into an evacuated space. Diffusion is the spread of one substance throughout a space or throughout a second substance. There is an equation that is the same for both effusion and diffusion. We can use this equation to help solve for the identity of a gas based on its molar mass.

            The last matter that we discussed was the deviation of real gases from ideal gases. This can be recognized by Van der Waal’s equation that corrects the ideal gas equation due to the finite volume occupied by the actual gas molecules and for the attractive forces that are present between gas molecules. This basically raises the pressure and lowers the volume.

Here is a video of methane bubbles in my hand being ignited

            I think this has been by far one of the hardest units that we have encountered yet. The material is pretty challenging and the concepts are hard to comprehend. It requires a lot more thinking about what is really going on than just plugging in numbers into the equation. I think the whiteboarding technique has really benefitted this unit because it allowed me to see all of the work for the problems we did and understand the concepts a little bit better. Participating in the liquid nitrogen lab was also very fun and educational. Overall this was a very full week. A lot happened and a lot was covered and that will only make this upcoming test all the more difficult.