My PBL Project

Introduction

This project demonstrates the law of conservation of energy through compressing cotton balls. Not only does it demonstrate the law of conservation of energy but it also demonstrates the conservation of momentum, potential and kinetic energy, and the laws of thermodynamics.

This is displayed through the driving question, which happens to be: what causes bits of cotton inside a small tube to ignite when you quickly compress the air inside the tube?

Materials:

PASCO compression igniter
Cotton ball, dry

There are three laws of thermodynamics. The first one stating that energy cannot be created nor destroyed. When pressure is exerted on the cotton ball, high temperatures are produced by adiabatic compression. Adiabatic compression is work done by an energy transfer to its system without a transfer of outside heat. The overall process is done extremely fast, which means that there is no time for external heat to enter the system.

This proves that adiabatic compression is taking place. The equation for adiabatic compression is PV^r = constant in which P is the pressure, V is the volume, and r is the ratio of specific heat. Therefore the more pressure that exerted on the force, the more heat the force will produce.

Scientific Principle

As stated in the introduction, principles covered include the law of conservation of energy, law of conservation of momentum, potential and kinetic energy, and the laws of thermodynamics.

Thanks for everyone who helped with the video :)

Procedure

This project is pretty simple, first you must gather you materials and clear work space. Then proceed to remove the piston from the compression igniter and place a piece of cotton ball in the bottom of the cylinder. Once this is completed, place the piston back in place and proceed to compress the piston in a quick, downward motion. Observe what happens to the cotton ball and record.

Investigation Part

Guiding questions to help answer the driving question:

· Remove the piston from the compression igniter, place a very small piece of cotton into the bottom of the inner cylinder, and then replace the piston. Using a quick, firm, downward motion, compress the piston and observe the cotton at the bottom. What happens to the cotton at the bottom of the cylinder?

-The cotton begins to ignite.

· What does the behavior of the cotton indicate about the temperature inside the cylinder when the piston is compressed?

- The ignition of the cotton indicates that the temperature rises as the piston is compressed

· Was heat energy transferred to the inner cylinder when the piston is compressed? If yes, where is the heat coming from? If no, why does the temperature inside the cylinder change?

-Heat energy was transferred into the inner cylinder.

· How does the volume of the cylinder change when the piston is compressed? Was work done to change the volume? If yes, what did the work?

- The volume decreases: the compression of the piston causes the area in which the cotton ball is resting to become smaller. Work was done: the object (me) that pressed down on the piston produced work.

· Based on your answer to the previous question, and assuming that no air escapes from the cylinder, what happens to the pressure inside the cylinder when the piston is pressed? How do you know?

- The pressure increases as the volume decreases. There is no possible place for the pressure to go, therefore the pressure builds up.

· What is the Ideal Gas Law and how can you use it, along with your answers to the previous questions, to explain why the cotton inside the cylinder underwent the change that it did when the air in the cylinder was compressed?

- The idea gas law “relates the variables of pressure, volume, temperature, and number of moles of gas within a closed system” 1 (PV=nRT). As the pressure of the area increases, the temperature also increased which caused the cotton ball to ignite.

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