My physical science class is doing an experiment on the mass of pennies. I hypothesized that newer pennies would have less mass because cheaper materials are being used. I found that before 1982, pennies were made from 95% copper/5% zinc, and after 1982 from 99.2% zinc/0.8% copper. The mass of pre-1982 pennies is around 3.3 gr, and after 1982 about 2.5 gr. This would seem to support the hypothesis that zinc has less mass than copper, but I can't find any information about mass on the different metals. All I can find is atomic weight, and I don't even know if this relates to mass. Would someone be able to give me information about the mass of metals or know of a website that would have this information?
What you want is the densities (mass per unit volume) of copper and zinc. Metal densites are readily available in chem and physics handbooks and online.
For example, try
http://www.coolmagnetman.com/magconda.htm
Here is a site that gives composition and mass by year for the penny.
http://www.physics.utoledo.edu/~alukasz/Penny_Composition.htm
You can find the density of each at www.webelements.com and click on copper (#29) and zinc (#30). The density of Zn is a little lower than that of copper and you can see that the penny changed to a lower mass with the new 97.5/2.5 Cu/Zn blend. The atomic mass of zinc is slightly higher than that of copper which means that a mole of Cu atoms weighs slightly less than a mole of Zn atoms.
My ratio above might be misinterpreted. Perhaps I sould have written 97.5%Zn/2.5% Cu.
To find information about the mass of different metals, you can refer to the periodic table. The atomic weight listed on the periodic table is the average mass of an atom of that element, expressed in atomic mass units (amu). Although it is not the same as the mass of a larger quantity of the metal, it can provide a relative comparison between different elements.
To determine the mass of a larger quantity of a specific metal, you can use the concept of molar mass. Molar mass is the mass of one mole of a substance and is expressed in grams per mole (g/mol). One mole of any element contains Avogadro's number of atoms (6.022 x 10^23 atoms).
To calculate the molar mass of an element, you add up the atomic masses of each atom in its chemical formula. For example, the molar mass of copper (Cu) can be calculated by adding the atomic mass of one copper atom, which is approximately 63.55 amu. Similarly, the molar mass of zinc (Zn) can be calculated using the atomic mass of zinc, which is approximately 65.38 amu.
However, keep in mind that molar mass is different from the actual mass of a penny made of a specific metal. The mass of a penny is influenced by factors such as density, thickness, and size. The difference in mass you observe between pre-1982 and post-1982 pennies is likely due to the change in composition rather than the absolute mass of the metals themselves.
To find more specific information about mass and other properties of metals, you can refer to reputable scientific databases or textbooks. Websites like the National Institute of Standards and Technology (NIST), the Royal Society of Chemistry (RSC), or Encyclopaedia Britannica can provide reliable information on the properties of different metals. Additionally, your school library or a librarian may be able to assist you in finding relevant resources for your research.