Measurement of Air Volume at Different Temperatures

Introduction

This experiment investigates the effect of temperature on the volume of air, demonstrating the principles of gas behavior as described by the ideal gas law. The procedure involves heating and cooling air in a flask and measuring the resulting changes in volume.

Assembly of the Apparatus

To begin, a one-holed rubber stopper is fitted with a short piece of glass tubing and inserted into a 250 mL Erlenmeyer flask. The flask is then placed in a 600 mL beaker filled with water and supported by a wire gauze on an iron ring and heated with a burner.

• Erlenmeyer flask: Used to contain the air sample.

• Glass tubing: Allows for the transfer of water and air.

• Stopper: Ensures a closed system for accurate measurement.

• Beaker with water: Provides a controlled environment for temperature changes.

Heating the Air in the Flask: Measuring the Higher Temperature

The flask is heated in boiling water to achieve a higher temperature. The temperature of boiling water is typically 100°C, while the initial temperature of cold water is 23°C (as noted in the handwritten annotations). The volume of water entering the flask is measured (example: 26.5 mL).

• Procedure: Heat the water to boiling and maintain for 5 minutes. Record the temperature using a thermometer.

• Purpose: To observe the expansion of air at higher temperatures.

Cooling the Air in the Flask: Measuring the Lower Temperature and Related Volume

After heating, the flask is cooled by removing it from the boiling water and covering the glass tubing with your finger. The flask is then placed in cold water, and the volume of water entering the flask is measured. This demonstrates the contraction of air at lower temperatures.

• Procedure: Cool the flask in cold water and measure the volume of water that enters the flask.

• Observation: The volume of air decreases as the temperature decreases.

Calculation of the Volume of Air at Higher Temperatures

To determine the volume of air at higher temperatures, water is used to fill the flask after heating. The volume is measured by pouring the water into a graduated cylinder. The measured volume will be greater than the value stated for the flask due to the expansion of air.

• Measured volume: The volume of water that fills the flask after heating.

• Comparison: The difference between the calculated and experimental values is analyzed.

Percent Error Calculation

The percent error quantifies the difference between the experimental and calculated values. The formula is:

• Purpose: To assess the accuracy of the experimental results.

• Application: Used to compare the measured volume of air to the theoretical value predicted by gas laws.

Key Concepts and Definitions

• Ideal Gas Law: Describes the relationship between pressure, volume, and temperature for a gas:

• Thermal Expansion: Gases expand when heated and contract when cooled.

• Percent Error: A measure of the accuracy of experimental results compared to theoretical predictions.

Example Calculation

If the experimental volume of air is 26.5 mL and the calculated value is 25.0 mL:

Summary Table: Experimental vs. Calculated Volumes

Additional info: The table above is partially inferred based on typical experimental results and the provided example values.

Conclusion

This experiment demonstrates the relationship between temperature and the volume of air, providing practical application of the ideal gas law and the concept of thermal expansion. Accurate measurement and calculation of percent error are essential for evaluating experimental results in chemistry.