This experimental protocol is designed to measure the volumetric thermal expansion coefficient of a liquid by observing changes in the height of an oil drop within a capillary tube as temperature varies. The experiment starts with setting up the apparatus, including securing the universal clamps, preheating the capillary tube, and preparing beakers with cold water and ice.
Measurements of the oil drop’s height are taken at various temperatures, using a thermometer and a stopwatch, while carefully adjusting the water temperature on the heating plate.
Educational Goals
- Understanding Volumetric Expansion: Participants will explore how the volume of a liquid changes with temperature, aiming to determine the liquid’s volumetric thermal expansion coefficient.
- Temperature Measurement Techniques: The experiment introduces methods for accurately measuring temperature and the height of a liquid in a capillary tube, enhancing participants’ familiarity with temperature-related measurements.
- Laboratory Instrument Manipulation: Students will practice using various laboratory instruments, improving their hands-on skills in conducting experiments.
- Fundamentals of Liquid Thermodynamics: Through this procedure, participants will gain insights into the basic principles of thermodynamics as they apply to liquids, including the relationship between temperature and volume.
This laboratory experience is crucial for understanding how temperature affects a liquid’s volume and for mastering precise measurement techniques in a laboratory setting.
Participants will develop practical skills in handling laboratory equipment, observing physical phenomena, and analyzing experimental data. Furthermore, this experiment underscores the significance of methodological rigor and accuracy in scientific experimentation, ensuring reliable and meaningful results. Through engaging in this activity, participants not only learn about the thermodynamics of liquids but also appreciate the meticulous nature required in scientific research, enhancing their overall competency in experimental physics and chemistry.
Protocol
1. Attach a universal clamp to each of the two universal stands above the heating plate.
2. Drop a few drops of oil on the watch glass.
3. Light the Bunsen burner and heat the capillary tube with thermal gloves by keeping it exposed to the blue flame and moving it back and forth for about 20 seconds.
4. Place the hot open (clear) end of the capillary tube onto the drops of oil prepared in step #2. The oil should rise by itself into the capillary tube.
5. Return the tube to its upright position (open end up) and wait for it to cool. Then, secure the capillary tube to the right-hand stand using a universal clamp and turn off the Bunsen burner.
6. Place the 250 mL beaker on the heating plate without turning it on, placing the magnetic stirrer inside the beaker.
7. Secure the thermometer to the left-hand stand using a universal clamp and place it vertically in the 250 mL beaker. Ensure neither the tube nor the thermometer touch the beaker’s sides.
8. Position the ruler behind the capillary tube to measure the height of the oil drop.
9. In the ice beaker, add tap cold water until the level reaches 250 mL.
10. Pour the cold water and ice into the beaker containing the capillary tube, ensuring the water level is above that of the oil drop.
11. Observe the water temperature and the height of the bottom of the oil drop once the temperature stabilizes.
12. Start the stirrer on the heating plate and time to measure the height of the drop and the water temperature.
13. Turn on the heating plate to low intensity (20°C) and wait for the temperature to increase by about ten degrees.
14. Observe the water temperature and the height of the oil drop again once stabilized.
15. Repeat steps 12 to 14, increasing the temperature by 10 degrees each time until the setup no longer allows for reliable measurements.
16. Turn off the heating plate and wait for complete cooling before concluding the experiment.
Note: The inside of the capillary tube has a radius of 0.5 mm.
Anticipated Outcomes
Participants explore Charles’s Law, which states that the volume of a gas is directly proportional to its temperature when pressure and the amount of gas are held constant. This experiment provides a visual and quantitative understanding of how gas volume changes in response to temperature variations.
- Temperature-volume relationship: As the temperature of the gas (in this case, air within the capillary tube) increases, the volume, indicated by the height of the oil drop, is expected to increase. Conversely, when the temperature decreases, the volume should decrease. This relationship is a direct demonstration of Charles’s Law. The inside of the capillary tube has a radius of 0.5 mm.
- Data collection and analysis: By systematically recording the temperature and corresponding oil drop height at various temperatures, participants will create a dataset that, when graphed, should show a linear relationship between temperature (in Kelvin) and volume, affirming Charles’s Law.
- Observation skills: Participants will refine their observation skills, noting how minute changes in temperature can result in measurable changes in the volume of gas.
Significance and Lessons Learned:
- Understanding gas behavior: The experiment deepens the understanding of fundamental gas laws, specifically Charles’s Law, showing how gases expand when heated and contract when cooled in a controlled environment.
- Real-world relevance: The principles demonstrated are applicable in various real-world scenarios, such as understanding the behavior of air in weather balloons, automotive engines, and even in meteorology for weather prediction.
- Scientific methodology: Participants learn the importance of precise measurements and the need to control variables to isolate the effects of temperature on gas volume. This reinforces the scientific method’s role in experimental design and data analysis.
- Critical thinking: Analyzing the results, participants will engage in critical thinking, especially if the outcomes deviate from the expected linear relationship, prompting investigation into possible sources of error or non-ideal gas behavior.
- Practical skills: Handling laboratory equipment like Bunsen burners, capillary tubes, and thermal gloves develop practical skills and reinforces the importance of laboratory safety protocols.
This experiment offers a comprehensive learning experience, merging theoretical knowledge with practical skills, enhancing participants’ understanding of gas laws and their competence in conducting scientific investigations.
Summary of Assignment by Grade Range
Grades 3-5 (Ages 8-10)
- Focus: Basic introduction to temperature and volume concepts.
- Activities: Observing simple demonstrations of how temperature affects the volume of liquids, basic safety instructions.
Grades 6-8 (Ages 11-13)
- Focus: Intermediate understanding of volumetric expansion and temperature measurement.
- Activities: Measuring temperature and liquid height in a capillary tube, recording changes in volume with temperature, following detailed safety protocols.
Grades 9-12 (Ages 14-18)
- Focus: Advanced understanding of volumetric expansion, precise measurement techniques, and thermodynamics principles.
- Activities: Setting up and using the apparatus to measure the volumetric thermal expansion coefficient, accurately measuring temperature and liquid height, analyzing the relationship between temperature and volume, detailed recording and interpretation of results, adhering to advanced safety protocols, reinforcing concepts of liquid thermodynamics.
Laboratory essentials
Instruments
Beaker (250ml)
Bunsen burner
Capillary tube
Dropper
Hot plate
Lab Stand & Clamps
Magnetic stirrer
Ruler
Thermometers
Timer
Watch glass
Products
Olive oil