How does the change in the number of gas particles change the pressure of gas in a glass beaker

Variables:

Independent variable

The amount of air in the beaker

Dependent variable

Pressure in the beaker

Controlled variables

Materials:

275 mL beaker

75 mL of water

Pressure gage

20 mL Syringe

Thermometer

Procedure:

Measure the temperature of air

Put 75 mL of water into the beaker

Make sure it is approximately the same temperature as of the air

Set up the pressure gage and the syringe like shown in the diagram below

Pull out 20 mL of air out of the beaker 5 times, and record the pressure every time air is sucked out of the beaker

Make sure to hold the syringe strongly, as the low pressure in the beaker will pull air back in

Repeat the previous step 5 times

Diagram:

Syringe

Pressure Gage

Beaker

Water

Data:

Below is the table showing all the five trials, including the average results. After finding the average of the pressures, the number of molecules was found using this formula:

The measurement error is 50 Pa. The measurement error and the random error are neglected, because the change in pressure is observed, and the multiple trials are done for removing random error.

This is the graph representing the dependence of pressure with respect to the amount of air:

        

        Conclusion and evaluation

Through this experiment it was concluded that the decrease of amount air leads to a decrease in pressure, just like an increase in the amount of air leads to the increase in pressure, meaning a direct proportionality, just as expected. Some of the mistakes include 18°C water instead of room temperature (20°C), which could have allowed some variation in the data. Other sources of error would include the device itself: it can be clearly seen that the pressure gage is not 100% precise, even though very close to it, which is the reason why there were 5 trials to eliminate that error, or at least minimize its effect.