To demonstrate that matter is conserved during a chemical change or reaction, you can use the following procedure involving a chemical reaction where the conservation of mass can clearly be observed:
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Combine Acid and Base:
- Measure and record the mass of a known mass of an acid (like hydrochloric acid) and a base (like sodium hydroxide).
- Combine them in a beaker or flask to produce water and salt (sodium chloride).
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React and Measure:
- After the reaction is complete, measure the mass of the resulting solution (containing the water and salt).
- This can be done by placing a lid on the container to prevent evaporation and to capture all products formed.
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Calculate and Compare Masses:
- Before the reaction, add the mass of the acid and the base together to get the total initial mass.
- After the reaction, measure the mass of the products (water and salt) and compare it to the initial mass. They should approximately equal each other, demonstrating the conservation of mass.
Alternative Procedures:
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Melting Butter:
- Measure the mass of a stick of butter, melt it, and measure the mass again. This shows that matter is conserved during a physical change (but not necessarily a chemical reaction).
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Burning a Log:
- Measure the mass of a log and then burn it. Collect the ash and measure it. However, some mass will be lost as smoke and gases during combustion, making it less effective for demonstrating mass conservation.
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Tearing Paper:
- Measure the mass of the whole paper and then tear it into pieces. This is a physical change and also demonstrates conservation of mass.
Conclusion:
The most effective way to clearly demonstrate conservation of mass during a chemical reaction is the first method involving the acid-base reaction, as the reaction results in a new compound and allows for easy measurement of all reactants and products without loss of matter to the environment.