Applications of first law

here we have our first experiment of the day that helped us understand the law of thermodynamics. A system was created with a glass syringe, tubing and a tubing clamp. Here we studied pressure, which is defined as the component of force that is perpendicular to a given surface per unit area of that surface. Given by the equation: P=F/A. In thermodynamics, potential energy is called internal energy and represents any way of storing energy inside the system. The internal energy of a system is the sum of the helter-skelter kinetic energies of atoms in a gas, the vibration of atoms in a crystal of quartz, or the spinning of gas molecules.  One way to increase the internal energy of a system is to do work on it.

Here are some concepts (formulas) for work and internal energy for our experiment. We derived the formulas for work as a function of pressure from the linear form of work, which is force multiplied by distance. 

We concluded that the transfer of heat energy to a system can either cause it to do work on it surrounding or increase its internal energy.

here we see the concept of change in internal energy. The relationship between absorbed heat energy, work done on surroundings, and internal energy change is true for any system. This is known as the first law of thermodynamics.

here we discuss the first law of thermodynamics a little further, and how molecules behave under specific circumstances.

Next experiment, we have a 1.0 kg bar of copper and it is heated at atmospheric pressure so that its temperature increases from 20 C to 50 C. We are asked "what is the work done on the copper bar by the surrounding atmosphere?" In this picture we see the calculations we did in class. 

Our answer to the questions was 0.0173J. Most of the energy transferred into the system by heat goes into increasing the internal energy of the copper bar. since the fraction of energy used to do work on the surrounding atmosphere is so small when we analyze the thermal expansion of the solid, the amount of work done by the system is usually ignored.

here we discuss kinetic energy and how molecules behave. This was related to what we seen on the computer generated molecular behavior of gas. we derived a mathematical relationship that relates pressure of the gas to the kinetic energy of the atom and the volume occupied by the gas.

The temperature of a gas is a measure of the Average kinetic energy of the molecules that make up the gas.

Here we discuss mean free path, molecular velocities. Mean free path consists of: d-diameter of the molecule (m), U-internal energy (J), N-number of molecules, P-pressure of gas (Pa), V-volume of gas m^3, and T-temperature (K). The we have molecular velocities which consists formulas related to: Normal average or mean speed, root-mean square and most probable. 

Here we discuss Adiabatic change which is another type of process that can occur during the expansion or compression of a gas. This type of process is defined as Q=0, which indicated that the system does not exchange heat energy with its surroundings. According to our notes from class, this type of process can be brought about by carefully insulating the system so that no heat energy exchange is possible, or by carrying out the process so fast that heat doesn't have time to be transferred.  

here we have our derivation. Note:  The exponent of 3/2 only holds for an ideal monatomic gas.  For a “real” gas the exponent will be different.

Next experiment, we used a fire syringe to test an Adiabatic change. This syringe allows a rapid compression of air in a small glass tube that is inside a safety tube. If pushed hard, the piston will be forced down, not completely, this will cause a compression that is near adiabatic.    

Heres a video of my group and I doing the experiment.

these are the calculations for the final temperature and the uncertainties of all variables.