- Read through the entire experiment before beginning.
- Record a hypothesis based on Charles law.
- Use the ring stand and clamp to suspend the Erlenmeyer flask in a 1,000 mL beaker as shown below.
- Prepare the stopper to fit the 250 mL Erlenmeyer flask by inserting a short piece of plastic or glass tubing. The end that is inside the flask must be even with the surface of the rubber stopper.
- Be sure the flask is dry.
- Fill the 1000 mL beaker with enough water to cover at least 75% of the suspended flask.
Heat the water to boiling, then reduce the heat and continue to boil for about 5 minutes. Record the temperature of the boiling water in the data table. You may draw a data table like the one below or
to print out chart.
- Close the top of the flask by placing your finger firmly over the end of the tube in the stopper. With that same hand, use a hot pad or gloves to grasp the neck of the Erlenmeyer flask and transfer the flask to tap water.
- Cool the flask by immersing it in either a bucket of tap water or another 1000 mL beaker or another container that will allow it to be mostly immersed. Keep track of the temperature by placing a thermometer in the water.
- Stir the water while keeping the flask closed until the temperature no longer changes and then record the temperature of the water.
- Leave the flask immersed in the water for five minutes with the flask and the end of the tube in stopper completely submerged and release your finger from top of the tube and allow water to enter the bottle.
- Hold the flask in an inverted position, with the tube still open and elevate or lower the flask until the water level in the flask is even with the water level in the beaker or whatever container you are using (as seen in video). Then place your finger back on tube and close the flask. The air in the flask is now at atmospheric pressure.
- Remove the flask from the water and place it right side up on the lab table or work surface.
- The volume of water that is in the flask is equal to the change in volume of the air as it cooled from the temperature of boiling water to the temperature of tap water. Use a graduated cylinder to accurately measure the volume of the water. (An estimate using the scale printed on the Erlenmeyer flask will not suffice.) Record your data in the row – “Volume of air at lower temperature”.
- To find the starting volume of the air in the flask, fill the flask with water. Use the graduated cylinder to accurately measure the volume of the water in the flask. Record your data in the row – “Volume of air at higher temperature”
- Obtain a clean flask and repeat steps 3 – 16, only cool the flask in the boiling water this time by immersing it in a beaker of ice water instead of tap water. (Note: Prepare an ice water bath before proceeding). Remember to record data; this set of data will go in part B.
Complete the following analysis and conclusion.
- Calculate the Kelvin temperatures of the water and record your answers in the data table.
- Find the change in the volume of air in the flask from your data and record in data table.
- Use the equation V1 / T1 = V2 / T2 to calculate the expected volume of air when cooled in tap water.
- How do the expected final volume and the actual final volume compare?
- What is the significance of elevating or lowering the flask until the water level in the flask is even with the water level in the beaker or container?
Construct a graph of the data. Plot the volume of the gas at room temperature in tap water and in ice water on the y axis. Plot the Kelvin temperature on the x-axis. Print out graph paper for your plot. (
for graph paper.)
- Extend the plotted line downward until it crosses the temperature axis. This process of extending a graph beyond the experimental data is called extrapolation.
- At which temperature is the line predicted to cross the x-axis?
- At which temperature did the line actually cross the x-axis?
- Account for any deviation betweeen the predicted temperature line extrapolation and the actual line extrapolation.
- Real World Chemistry – Explain why bottled gas containers are equipped with a relief valve?