Questions
- According to the result of the experiment, the relationship between variables such as volume and pressure was inversely related. However, the graph that showed the relationship between 1/volume and the pressure was directly related.
- Gas law was defined by many scientists. However, the relationship between volume and pressure was proved by Boyle who made Boyle’s laws which defined pressure and volume are inversely proportional. If the pressure goes up, the volume will go down and vice versa. However, if we put the volume inversely, then the relationship between pressure and the inversed volume will be changed into directly proportional.
- KMT (Kinetic molecular theory) helps to explain macroscopic properties of gases such as pressure, temperature of volume, by considering their molecular composition and motion. It says that pressure is due to collisions between molecules moving at different velocities. If the gas is in a container, the collision with the wall is instantaneous and elastic. Therefore, its shape is changeable by pressure or temperature. However, at some point, the volume does not change little when there is no more space between molecules or the collision with wall is stronger than the pressure. As we can see in the result of the experiment, there is bigger difference between weak pressures and smaller difference between strong pressures. At the end there is almost no difference between pressures. The other graph that volume was inversely drawn shows constant increase which is directly proportion. We can also find the shape of graph from the equation. The origin equation of Boyles’ law is P∝1/V → P=k(1/V) → PV=k.
Conclusion
From the experiment, I was able to determine the mathematical relationship between pressure and volume. According to the Boyles’ law, Pressure*Volume has constancy because pressure and volume are inversely related to each other. To find out the pressure, I had to fine out the mass and the area of contact because the pressure has a formula (Mass/Area). According to the formula, the pressure of a book had 251g/cm² (1440/5.73 = 251g/cm²). Therefore, the pressure will be constantly changed by the number of books. It is not the end of the pressure. I had to add the total pressure on the piston equals the pressure from the books plus the atmospheric pressure. For the volume part, I just had to record the scale of syringe that shown according to the number of books. The more books press the syringe, the less scale of volume was shown. From the Boyles’ law, P∝1/V → P=k(1/V), PV=k(constant) can be deduced. Form the mathematical calculation based on the Boyles’ law, the volume was exactly decreased, when the pressure was increased. In addition, Pressure*Volume showed the constancy, even if it contained huge uncertainties. Therefore, the conclusion will be same as Boyles’ law that the pressure and the volume are inversely proportional. To make the graph which shows the relationship between pressure and volume more understandable, I supposed the small numbers (50-1000) of pressure that would give much bigger volume by dividing constant from pressure. According to the graph, smaller number of pressure has bigger number of volume, and vice versa.
Limitation
There were a few limitations in my laboratory. First of all, as you can see in the volume part, there is no volume difference between no book and with a book which means there was not any pressure between these. I think that was because of the supporting thing which was the top of the syringe where we put the books. It seemed that it had reasonable weight as much as a book had. Secondly, there were huge uncertainties between theory and my experiment as we can assume that the experiment is not reliable. For example, the uncertainty of constant of Pressure and Volume, it had 8% of uncertainties so the biggest constancy was 1200 (highest constancy was 46,900 ±3750 - the lowest constancy was 45,700 ±3660) Moreover, I found that there was not constant pressure due to the unstable syringe, I had to make the balance point so my pressure by hands might influence the results.
Improvement
Fortunately, my experiment had a few odd points so it was rather successful. However, to improve my experiment, I need to figure it out the mass of the support thing that was on the top of the syringe. Due to the resistance by supporting stuff, there was not any volume difference between no book and a book. For the next time, we may find how much it can support it so we can subtract that weight. There were huge uncertainties that prove the results are not reliable. To reduce the uncertainties, we need to measure more accurately with more significant digits. Also, I can do more trials to make the result more accurately. Besides, we need to find more stable equipment that we do not need to find the balance point and put pressure by hand accidently. In addition, make it sure that the gas which was blocked to be released by piston should not be leaked. Lastly, when any scale is measured, make it sure that all of them are accurate so that the uncertainty will be less which means the experiment will be more reliable.
