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Chem Lab report (2) - Ayza Taimur Abstract In this lab we...

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Ayza Taimur Abstract : In this lab, we measured the mass and volume of pennies and calculated the density of both. We found the density of old and new pennies and explained the difference in their densities. We also calculated the density of zinc and copper which are used in making pennies. We found out the reason why older pennies have more mass than the newer ones which is because there is more copper in them than zinc. Newer ones have more zinc and less copper. Introduction : We did this experiment to see what year the pennies that were minted in the United States had changes in their composition. The theory behind this experiment is that, before 1982 pennies that were minted in the United States were 95 % copper and 5% zinc. The density of copper is 8.92 g/mL and the density of pure zinc is 7.14 g/mL. After 1982, the composition of the pennies was changed. The new pennies had 97.5% zinc and 2.5% copper. The composition of pennies was changed because copper was worth more than a penny. The mint decided to make the pennies with more zinc and a thin layer of copper in them. In this experiment, we found out that the density of old pennies is lower than the density of newer ones. We used the equation: Density=mass/volume to find the density of old and new pennies, zinc and copper. We also used a formula to calculate the percent error in the end. The equation for % error is [(Correct value – experimental value)] / Correct value * 100%. We used this equation to calculate the percent error in the densities of old and new pennies and the densities of zinc and copper. We also found the standard deviation of our individual penny volumes and that of the class. We also graphed the mass of pennies vs. the year they were made, mass vs. volume
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