Thermodynamics

Lab Day 4: 3/5/15 First Law of Thermodynamics and Gases

Relationships between Work and Gas:

We analyzed the relationship between work and gas where we found that work is the area under the curve of pressure versus volume. There is also internal energy which is caused by heat. We can see based on this graph that there is no work done when the volume is constant. In fact the work done on the system does depend on its path where the initial and final states are not the only variable.

Area under Pressure vs distance and volume curve

Kinetic Energy Model:

Kinetic Model

For the kinetic energy model, we looked at atoms in a software that collides elastically in a two dimensional box. In fact when we saw that as the volume increases, the amount of collision also decreases in which pressure would decrease. We found that the speed of gas particles could be found using the root mean square speed.

Kinetic Energy Model Derivation Part 1

Kinetic energy Model Derivations part 2

Adiabatic Conditions:

Adiabatic Compression of Gas

There is no change in pressure, but there is change in gas and volume.

Fire Syringe Experiment: Rapid Compression of Gas

Fire Syringe Experiment

In order to analyze the rapid compression of air, we used a device called a fire syringe that when compressed rapidly, the cotton on the bottom would ignite due to the compressed air.

Apparatus: Fire syringe with cotton inside compressed air in adiabatic conditions that sparks at high temperatures.

As a result, as we pushed the syringe down quickly, we observed a rapid spark of fire. We took measurements of the initial states of the syringe including the length of  the air column, inner radius, volume, and temperature. The final temperature was calculated to be  351 degrees K which is incredible in temperature difference. The burning temperature of paper is 451 degrees F. There was no heat exchange where it was adiabatic in a plastic cylinder. Therefore, according to the first law of thermodynamics, the change in internal energy is equal to the negative work being done. So as the volume increases, the temperature and pressure decreases. In this case, as the piston is lowered rapidly causing a rapid decrease in volume is seen to have caused an instant increase in temperature.

Uncertainty and Uncertainty Propagation:

We used a digital caliper to measure the length of the syringe and the inner diameter which accounted for an uncertainty of +/- 0.0001 m. The volume was found using the length measured by the same caliper which should have an uncertainty of approximately 0.0005 m. The temperature was measured with an uncertainty of 0.0005 m.
First Law of Thermodynamics:

First Law of Thermodynamics

Relationship of work,heat,internal energy