Population tables. of world cities. This article lists the most populous cities in the world defined according to a concept of city proper. A city proper is a locality defined according to legal or political boundaries and an administratively recognised urban status that is usually characterised by some form of local government. Cities proper and their boundaries and population data may not include suburbs. World Urbanization Prospects, a UN publication, defines population of a city proper as the population living within the admi
The mass of one cubic centimeter of copper is 8.96 grams, while the mass of the same amount of zinc is 7.13 grams. 1  A penny is made of copper and zinc. 2  Copper is heavier than zinc. 3  The cost of copper has been on the rise during the past couple of decades.
At the very least, a change in the composition of the American penny seems likely. In 1982, Congress authorized the Treasury to make such a change, and it did. Before then, pennies were 95 percent copper and 5 percent zinc, Mr. White says. Pennies manufactured since have been copper-plated zinc, with zinc making up 97.5 percent of the coin and copper only 2.5 percent. Steel, which was used in pennies in World War II, could be substituted next.