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A new penny has a mass of 2.49 g and a volume of 0.349 cm ^{3}. Is the penny made of pure copper? Explain.

Hey guys, in this question we're asked if a penny is made of pure copper so here they tell us that the penny weighs 2.49 grams and that it has a volume that is 0.349 centimeters cubed, now how can we determine if it's made up of pure copper, well to answer this question we have to find the density of copper so if you look within the chapter you'll see the table of densities of different types of substances and the density of copper remember density equals mass over volume, the density of copper according to your book here is 8.96 grams per centimeters cubed so what we would do here is that we would calculate what the density is here we take the 2.94 grams and divide it by the 0.349 centimeters cubed when we do that that gives us 7.13 grams per centimeters cubed so the penny has a density that is different from the density of pure copper so the penny is not made of pure copper and in fact pennies have stopped being made of pure copper decades ago. During the world wars, they had to conserve precious metals such as copper and so gradually they were taken out so as a result we can say here since the densities don't match and this is the density of pure copper since the densities don't match that means that the penny isn't made up of pure copper.