Lesson
Purpose of the work:
- To study the effect of acetic acid on eggshells.
- To demonstrate the solubility of calcium carbonate in acid.
- To draw conclusions about the role of calcium in the human body.
Expected results:
After completing the work, students can:
- develop teamwork skills
- be able to analyze and summarize the information received
- draw logical conclusions
Teacher’s Guide:
- The task is performed in pairs
- Before starting laboratory work, please read the safety rules by following the link:
- To download the worksheet, follow the link:
Theory
Calcium is one of the most important macronutrients necessary for the proper functioning of the human body. It plays a key role in the formation and maintenance of healthy bones and teeth, blood clotting, muscle contraction, transmission of nerve impulses, and regulation of many other vital processes.
Eggshells are a readily available and inexpensive source of calcium. They consist mainly of calcium carbonate (CaCO₃), a compound that dissolves in acids to form calcium ions (Ca²⁺) and carbon dioxide gas (CO₂).Acetic acid (CH₃COOH) is a weak acid that can react with calcium carbonate contained in eggshells.
Practical part
Step 1: Carefully place a raw chicken egg in a clear glass and completely cover it with white vinegar.
Step 2: Leave the glass undisturbed for 24 hours. Observe the egg periodically, noting any formation of gas bubbles on the eggshell and changes in its appearance.
Step 3: After the specified time, gently remove the egg from the vinegar solution and rinse it thoroughly with water. Compare the egg’s initial and final states, recording changes such as the disappearance of the shell, alterations to the egg white’s transparency, and any unusual odors.
Step 4.Write the balanced chemical equation for the reaction between calcium carbonate in the eggshell and acetic acid.
Step 5. Draw conclusions about the chemical reactions taking place and the role of calcium in the structure of the eggshell. Fill in the table in your Worksheet:
Table 1.
| Duration | Observations | Conclusion |
Conclusion:
This laboratory work helped the students to learn more about the properties and importance of calcium for human health.