Identifying Unknown Substances using Pop Test and Lime Water Test

Introduction

• Purpose: Determine the identity of four unknown substances using pop test (for hydrogen gas) and lime water test (for carbon dioxide gas).
• Tools: Recorded video for anyone who missed the live experiment.
• Objective: Enable all students to complete the report and secure assessment marks.

Experimental Setup

• Equipment: Test tubes, matches, acid, distilled water, lime water, gas delivery tube.
• Samples: Four unknown chemical samples labeled as X1 to X4.
• Test Procedures:
  • Pop Test: Checks for the presence of hydrogen gas.
  • Lime Water Test: Checks for the presence of carbon dioxide gas.

Experiment Steps

Pop Test Procedure

1. Sample X1: Metallic strips
   • Observation: Bubbling observed upon adding acid.
   • Result: Positive pop test (squeaky pop sound).
   • Conclusion: Producing hydrogen gas; therefore, X1 is a metal.
2. Sample X2: White powder (like flour)
   • Observation: Bubbling observed upon adding acid.
   • Result: No pop; match went out.
   • Conclusion: Not a metal. Proceed with lime water test.
3. Sample X3: White powder (like icing sugar)
   • Observation: Bubbling observed upon adding acid.
   • Result: No pop; match went out.
   • Conclusion: Not a metal. Proceed with lime water test.
4. Sample X4: Blue solid powder
   • Observation: No bubbling upon adding acid.
   • Result: No gas produced.
   • Conclusion: Cannot be a metal or carbonate, must be a neutral salt.

Lime Water Test Procedure

1. Sample X2:
   • Observation: Lime water turned milky quickly.
   • Conclusion: Producing carbon dioxide gas; therefore, X2 is a carbonate.
2. Sample X3:
   • Observation: Not enough gas produced for a valid test.
   • Conclusion: Inconclusive from lime water test. Likely to be a carbonate due to the gas production, but lacked conclusive result.

Results Summary

• X1: Positive pop test; identified as a metal.
• X2: Lime water test turned milky; identified as a carbonate.
• X3: Inconclusive lime water test; suspected to be a carbonate (Not Metal).
• X4: No gas produced; identified as a neutral salt.

Analysis and Discussion

• Integrity in Science: Present results truthfully, even if they suggest inconclusive findings.
• Key Insight: A clear structured approach using multiple tests can help deduce chemical identities logically.

Conclusion

• Understanding and correctly performing identification tests are crucial in practical chemistry.
• Documentation should reflect accuracy and critical thinking.
• This experiment provided hands-on experience with identifying metals, carbonates, and neutral salts based on gas production reactions.