To demonstrate that matter is conserved during a physical change, you can perform a simple experiment involving a closed system. Here’s a step-by-step procedure you can follow:
Materials Needed:
- A sealed container (e.g., a balloon, a jar with a lid)
- A thermometer (optional)
- A scale or balance
- A measurable amount of a substance (e.g., water or ice)
- A heating source (if using water)
Procedure:
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Weigh the Initial Substance:
- Measure and record the mass of the container (if using one) and the substance you will use (e.g., water) in its initial state. For example, if you are using ice, weigh the container with the ice.
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Conduct the Physical Change:
- If you are using ice, place the container with the ice in a controlled environment (like room temperature) or use a heating source to melt the ice into water. Ensure that the container is sealed to prevent any mass loss due to evaporation or spillage.
- Alternatively, you could just change the state of matter from liquid to gas or vice versa while keeping everything sealed.
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Weigh the Final Substance:
- After the physical change is complete (e.g., the ice has completely melted into water), weigh the container and the resultant substance together again. This includes measuring both the container and the water (or gas, depending on your experiment).
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Compare the Masses:
- Compare the initial mass (before the change) to the final mass (after the change).
- If the container was included in both measurements, you can also measure only the matter itself (e.g., water or ice) before and after the change for a more direct comparison.
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Analysis:
- Ask students to analyze the data: Did the mass change?
- Discuss the concept of conservation of matter: Matter should remain constant in a closed system, regardless of changes in state (solid, liquid, gas).
Conclusion:
This experiment shows that during physical changes, such as melting or freezing, the total mass remains the same when measured in a closed system, illustrating the law of conservation of mass. If tightly controlled, any discrepancies can be attributed to measurement errors or loss of material due to spillage or evaporation, reinforcing the importance of using a closed system for such demonstrations.
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