This laboratory experience is meticulously crafted to unravel the mysteries of different unknown gases by closely observing their reactions to incandescent wood and their interactions with lime water. The primary focus is to explore the gases’ abilities to sustain or extinguish the combustion of a wooden splint and to detect chemical reactions indicative of specific gases, particularly the identification of carbon dioxide through the formation of a white calcium carbonate precipitate. This hands-on approach not only bridges the gap between theoretical concepts and real-world application but also enriches the understanding of the chemical and physical properties of gases
Educational Goals
Understanding Gas Properties: Gain a comprehensive understanding of the chemical and physical properties of gases, focusing on their behavior in the presence of flame and chemical reactivity.
Experimental Observation: Learn to conduct experiments to observe the reaction of different gases when exposed to an incandescent wooden splint, distinguishing between flammable gases, those that support combustion, and those that extinguish flames.
Chemical Reaction Analysis: Develop skills in conducting chemical tests, such as the addition of lime water to gas samples, to observe and analyze chemical reactions indicative of specific gases, particularly the detection of carbon dioxide.
Theoretical Application: Apply theoretical knowledge of gases to practical experiments, enhancing the ability to identify gases based on their properties and reactions.
Safety and Procedure: Emphasize the importance of safety and adherence to procedural protocols while handling gases and conducting experiments.
Analytical Skills: Enhance analytical skills through the observation of experimental outcomes, fostering a deeper understanding of gas properties and the interpretation of results.
This laboratory endeavor is designed to empower students with the knowledge and skills to experimentally identify the properties of different unknown gases through observation and chemical analysis. By engaging in this practical exploration, students are provided with a unique opportunity to directly apply their theoretical understanding to real-world scenarios, thereby enhancing their comprehension and appreciation of the fascinating world of gases.
Protocol
1. Light the wooden splint.
2. Remove the stopper from one of the test tubes containing unknown gas #1 (test tubes 1 to 3) and quickly introduce the lit splint.
3. Repeat steps 1 and 2 with one of the test tubes containing unknown gas #2 (test tubes 4 to 6) and one of the test tubes containing unknown gas #3 (test tubes 7 to 9).
4. Light another wooden splint.
5. Shake the splint to extinguish it while keeping it glowing.
6. Remove the stopper from a second test tube containing unknown gas #1 and quickly introduce the glowing splint.
7. Repeat steps 4 to 6 with the other two gases.
8. Open the third test tube containing unknown gas #1 and quickly pour in about 15 mL of lime water.
9. Immediately replace the stopper on the test tube and shake.
10. Repeat steps 8 and 9 with the test tubes containing unknown gas #2 (test tubes 4 to 6), then with those containing unknown gas #3 (test tubes 7 to 9).
Anticipated Outcomes
The unknown gas #1 is CO2 (g).
The unknown gas #2 is O2 (g)
The unknown gas #3 is H2 (g).
Review of the 3 steps of the experience:
Introduction of a burning splint into the test tubes containing unknown gases: This step is critical in identifying the presence of oxygen (O2). When a glowing splint is introduced into a tube containing oxygen, the splint will reignite, demonstrating oxygen’s role in supporting combustion.
Introduction of an extinguished but still glowing splint into the test tubes: This step helps identify the presence of hydrogen gas (H2). Hydrogen gas is known to reignite a glowing splint with a characteristic ‘pop’ sound, which is a result of the rapid combustion of hydrogen in the presence of oxygen.
Shaking lime water with the gas in the test tube: This step is designed to detect carbon dioxide (CO2). When CO2 is introduced into lime water (a solution of calcium hydroxide), it reacts to form calcium carbonate, which is insoluble and turns the lime water milky. This is a qualitative test for the presence of carbon dioxide. The significance of these tests lies in their ability to demonstrate fundamental chemical properties and reactions, such as oxygen’s role in combustion, the flammability of hydrogen, and the reaction of carbon dioxide with lime water. These experiments are not only foundational in understanding chemical reactivity and gas identification but also have practical implications in various scientific fields, including environmental science, safety protocols, and industrial processes. Through these simple yet effective tests, students or researchers can gain insights into the reactive behaviors of different gases and apply this knowledge in practical or experimental contexts.
Summary of Assignment by Grade Range
Grades 3-5 (Ages 8-10)
- Focus: Basic introduction to gas identification and simple observations.
- Activities: Observing gas reactions with a wooden splint and lime water, basic safety instructions.
Grades 6-8 (Ages 11-13)
- Focus: Intermediate understanding and application of gas identification techniques.
- Activities: Conducting experiments, recording observations, understanding chemical reactions, and following detailed safety protocols.
Laboratory essentials
Instruments
Lighter
Test tubes
Wooden Hatches
Products
Unknown gases (#1 to #9)