Suppose the densities of two metals are so close together that density is difficult to use to be able to distinguish them within the margin of error (a good example would be zinc and tin). What other physical properties could you use to determine which metal was which? Explain your reasoning thoroughly.

You receive a mixture of table salt and sand and have to separate the mixture into pure substances. Explain how you would carry out this task. Is your method based on physical or chemical properties? Explain.

How do you distinguish (a) chemical properties from physical properties? (b) distillation from filtration? (c) a solute from a solution?

On October 21, 1982, the Bureau of the Mint changed the composition of pennies (see Exercise 120). Instead of an alloy of 95% Cu and 5% Zn by mass, a core of 99.2% Zn and 0.8% Cu with a thin shell of copper was adopted. The overall composition of the new penny was 97.6% Zn and 2.4% Cu by mass. Does this account for the difference in mass among die pennies in Exercise 120? Assume the volume of the individual metals that make up each penny can be added together to give the overall volume of the penny, and assume each penny is the same size. (Density of Cu = 8.96 g/cm3; density of Zn = 7.14 g/cm3).