Title: Temperature vs. Volume of a Gas Purpose: To determine what happens to the volume of a gas sample as the temperature doubles. Materials: 1 Be ral thin-stem pipette, hot plate, 2 beakers of water, CBL temperature probe Procedure: 1. Take a large beaker of room temperature water and record its temperature. 2. Determine the volume of the be ral pipette by completely filling it with water and then holding it in a vertical position to squeeze out and count the number of drops of water it holds.
At room temperature, the “empty” pipette contains air which occupies a volume that can be expressed as the number of drops observed and recorded. DO NOT squeeze the pipette again unless you are counting drops. 3. Place a small beaker of water on a heat source and increase the temperature of the water approximately 8^0 C.
Remove the beaker from the heat source and allow the temperature to stabilize. 4. Place the empty pipette bulb into the hot water and agitate the pipette to increase the contact between the pipette bulb and the water molecules. After two minutes, flip the pipette and immediately submerge the tip into the large beaker of room temperature water.
DO NOT squeeze the pipette. Record the temperature of the heated water at the time you removed the pipette. 5. Observe the water moving into the pipette until water movement ceases.
Hold the pipette vertically and squeeze to count the additional drops of water now in the pipette. Added to the initial pipette volume, this will be the total gas volume at the new temperature. 6. Repeat steps 3-5 to obtain additional data points. Do not heat above 70^0 C.
Data Table: Initial Volume of pipette (drops) = 137 Linear Regression: Graph: Questions: 1. What temperature scale is used when working with changes in gas volumes as conditions such as temperature or pressure vary? The Kelvin temperature scale is used. 2. By examining the graph of temperature vs. Volume, what is the relationship between temperature and volume? What is the general equation for this relationship? The relationship is a direct variation relationship. The general equation is Charles’ Law: (V 1) (T 2) = (V 2) (T 1) 3.
From your graph, choose two temperature points (T 1 and T 2) and find the volumes that correspond to those temperatures. If V = kT is the equation representing the relationship between temperature and volume, solve for k using each set of data and compare the calculated values of k. How does your value for k compare to values other students in the class are getting? What does this imply about the value of k? Data Set 1: = . 4576 Data Set 2: = .
460 Data Set 3: = . 466 Data Set 4: = . 462 Data Set 5: = . 462 Our data was close to everyone else’s data. This implies that the value of k is constant. 4.
What is the significance of the point at which the extrapolated line (V = kT) crosses the horizontal axis? It is absolute zero. 5. What are sources of error in the experiment? Explain. 1.
We didn’t hold the pipette completely vertical. 2. We heated the water above 70 oC 3. We didn’t count the initial drops of water correctly. 6. If the volume of a gas is 250 mL at 25 oC, what volume will it occupy at 35 oC? 250 mL = V 2 250 mL = V 2 V 2 = 258.
3925 oC 35 oC 298 o K 308 o K 7. Increasing temperatures cause greater volumes of water to move into the pipette. Is it feasible to have water completely fill the pipette? Explain. No. You can’t compress air to the point of nonexistence. Conclusion:.