Internal Energy, Work, And Heat

Purpose:   In this experiment, we take a look at the relationship between work, heat, and internal energy. We will go over the relationships between heat, work, and internal energy using pressure, volume, and temperature.

Definition of Work 

To begin, we went over the definition of work. We knew that work was equal to the integral of force dot with dx, or the product of force and distance and cosine theta. We re-wrote the definition of work in terms of pressure and volume knowing that the pressure times the area gives us the force.

Work Done on a Syringe

We take a look at an experiment done in the previous lab concerning volume versus temperature. We see that work is done on the syringe when we heat it because the back of the syringe moves upward. We show on our boards that the molecules move faster and faster and bounce off walls. This inevitably causes work.

Explanation of Thermodynamics

In order to truly understand what it is meant by thermodynamics, we had to come up with an explanation that made sense to us. This is what we came up with. Underneath, we provided some examples of having work without heat produce internal energy and heat without work produce internal energy.

Force Using Impulse

We look further into force by rewriting it in terms of impulse. This becomes necessary when we talk about the microscopic activity of particles in a confined space that collide with the walls and create pressure.

Rearranging The Variables

Professor Mason goes over with the class the significance of the previous derivation and the relationship between pressure and volume. Many substitutions were made, such as Vx to Vt and cubic x to V for volume.

We conclude that there is a relationship between pressure, volume, and kinetic energy.

Vrms

We use the derivation of the relationship between pressure, volume, and kinetic energy to derive our Vrms (or the root mean square velocity)

Work Equals To Heat

We examine the relationship between volume and temperature in an adiabatic and isothermal process.

Creating Fire Using Pressure

In our video, we demonstrate fire created by increasing the pressure while decreasing the volume. But, it is not that simple. In order for this to truly work, the change in volume had to happen in a small time interval. This is also shown in our video, as it took us a couple of tries to get it right.

Evaluating The Givens of a Syringe

Given the values at the initial point and the final point, we had to find the final temperature without knowing the area of the object.

Estimating a Syringe

In the lab manual, we estimated the final temperature of the syringe experiment above and compared the value of final temperature to the temperature of flash point. The temperatures were not the same, as there was a 70 degree Fahrenheit difference, which can undoubtedly be due to the estimation but the final estimated temperature is still pretty high, considering that we go from a room temperature of 298 to 469, which is almost double.


Conclusion:  After carefully examining the relationships between pressure, volume, and forces, we were able to undergo analysis of the characteristics of particles in a closed space. We derived values, such as Vrms using what we knew about the behavior of molecules. We know that molecules travel in straight paths and collide with each other in many directions in 3 dimensional space; therefore, it was crucial for us to derive a generalized velocity for all the particles. It was also surprising that we had to create a flame using a rapid change in volume, as we quickly compress the air to increase the temperature.