Combined Gas Law Lab Report HJM Research

Combined Gas Law Lab Introduction: The combined gas law is the relationship between the volume, temperature and pressure. The purpose of this lab is to either confirm or reject the combine gas law. Gas is a state of matter in which molecules move in a random molecular motion. Pressure in gas is caused by the collision between particles and a surface. Pressure can be changed by the volume, amount of space, or temperature. Pressure and volume have an inverse relationship which is the principle of the Boyle’s law. Thus, if one goes up the other goes down or stays the same, due to the collisions of particles increasing when the volume or space is decreased. Yet, the Charles’s law shows the proportional relationship between volume and temperature, meaning if one goes up so does the other. If heat increases the particles random molecular motion increases as well, thus, increasing the collisions of particles and spreading which increases the volume. Procedures: The relationship between pressure and volume 1. The syringe was set to 20 mL. 2. The tip was connected to the tubing which was already connected to the gauge. 3. The initial volume was recorded. 4. The syringe was compressed by 2 mL and the pressure was recorded. 5. Steps four was repeated until the needle reached 710 mmHg. 6. The gauge pressure was converted to absolute pressure by adding 760 mmHg.

The relationship between volume and temperature 1. The syringe was placed at 30mL and capped.

2. The thermometer and syringe were placed in a 400 mL beaker filled with water. 3. The current air temperature was recorded from the wall thermometer. 4. The water was heated at 65 degrees Celsius and the volume of the syringe was recorded. 5. The water was then heated to a 100 degrees Celsius and the volume of the syringe was recorded. Results: Table 1: The relationship between volume and pressure of a gas Volume (mL)

Gauge Pressure

Absolute Pressure

Predicted Pressure

20

0

760

760

18

40

800

844.44

16

140

900

950

14

260

1020

1085.71

12

350

1110

1266.67

10

510

1270

1520

Table 2: The relationship between volume and temperature of a gas Temperature Absolute (°C) Temperature (K) 25 298 65 338 100 373

Volume (mL) 30 33 47

Predicted Volume (mL) 30 34.03 37.55

Graph 1: Calculation between volume and pressure of a gas

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Helen J. Mendez Feb. 10, 2013 P. 4

Graph 2: Calculation between volume and temperature of a gas

Calculations: (See attached) Conclusion:

The combined gas law was confirmed in the experiment; it confirmed the inverse relationship between volume and pressure and the proportional relationship between temperature and volume. The Boyle’s law was seen in the relationship between volume and pressure. This inverse relationship between volume and pressure was presented in the data table. According to the observations, when 20 mL decreases to 18 mL, the pressure increases from 760 mmHg to 800 mmHg. Thus, when the volume decreases the pressure increases. However, in the graph, the experimental data was not equivalent to the predicted data indicating a source of error. A plausible source of error in the experiment would be a leak from the tubing. This leak would have let air escape meaning less particles and moles. Therefore less moles signifies fewer collisions which would decrease the amount of pressure. Thus, this source of error causes the data to no concur with the predicted. In addition to the Boyle’s law being proved, the Charles’s law was also confirmed in the experiment. The proportional relationship between volume and temperature was demonstrated in the data table. As can be seen on the data table, when the absolute temperature increases from 298 K to 338 K so does the volume; it increases from 30 mL to 33 mL. Hence, if one goes up so does the other. Yet, on the graph the experimental data did not coincide with the predicted; thus implying a source of error. The conceivable source of error in this experiment would be more moles of gas were in the syringe. Thus, water was already in the syringe which turned into gas when the water reached boiling point. This extra gas caused there to be more moles which increased the collisions of particles; the particles spread due to the random molecular motion and increased the volume. In conclusion, the experimental data did not overlap with the predicted because of the amount of moles in the syringe which caused the sudden increase in volume.

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Helen J. Mendez Feb. 10, 2013 P. 4