The procedure you've outlined could demonstrate the principle of conservation of mass, but it would need to be properly designed to clearly reflect a chemical change. Melting butter primarily involves a physical change (from solid to liquid) rather than a chemical reaction.
To effectively demonstrate conservation of mass during a chemical change, you can follow these steps using a chemical reaction instead:
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Choose a Chemical Reaction: Select a straightforward chemical reaction, such as the reaction of vinegar (acetic acid) and baking soda (sodium bicarbonate) to produce carbon dioxide gas, water, and sodium acetate.
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Set Up Your Apparatus:
- Use a closed container (like a flask with a stopper) that can hold the reactants.
- Make sure you have a precise scale to measure the mass.
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Measure the Mass:
- Weigh the empty closed container and record its mass.
- Add a known amount of vinegar to the container and weigh it again.
- Next, add a known amount of baking soda to the container and quickly seal it to prevent gas from escaping. Weigh the setup again to get the total mass.
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Conduct the Reaction:
- Allow the reaction to proceed. You can gently swish the container to help mix the reactants as needed.
- Once the reaction is complete, you will see bubbling due to the release of carbon dioxide gas.
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Re-weigh the Container:
- After the reaction has finished, weigh the container again with all the products inside (the dissolved sodium acetate, water, and any remaining bicarbonate).
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Analyze the Results:
- Compare the total mass before the reaction (mass of the container with vinegar and baking soda) to the total mass after the reaction. According to the law of conservation of mass, the masses before and after the reaction should be equal, demonstrating that matter is conserved during the chemical change.
This way, you showcase a clear chemical change while effectively demonstrating the principle of conservation of mass.