Pre-1982 Pennies and Post 1982 Pennies

Based on my data, my hypothesis turned out correct. The pre-1982 pennies did have a greater density than the post 1982 pennies. The density of the pre-1982 pennies' eighth trial was about 8.89 g/cm cubed, while the density of the post 1982 pennies' eighth trial was about 7.27 g/cm cubed. I could also tell the density was greater because, the cumulative mass of the pre-1982 pennies was more than the mass of the post 1982 pennies. Even with changes in chemical composition, the volume for both penny groups was about the same. This is mainly because the sizes of the pennies stayed the same before and after 1982.

After doing this experiment, we extended our knowledge on density, by doing another density lab. However, this second lab dealt with densities of liquids. In this lab, each group had to find the density of a mysterious liquid. To find the mass of a liquid, we first found the mass of the dry and empty 10 mL graduated cylinder (21.68 grams). Then, we found the mass of the graduated cylinder with the liquid (30.48 grams). After finding both masses, we subtracted the mass of the full graduated cylinder from the mass of the empty graduated cylinder. Our final mass was 8.80 grams and our final volume was 9.25 mL. To find the volume, we simply read the volume of the liquid directly from the graduated cylinder. The mass divided by the volume gave us an experimental density of about 0.95 g/cm cubed. We were close, for the true density of the liquid was 0.98 g/cm cubed.

After everyone found the density of their liquid, we arranged the liquids by their density, from greatest to least. Then, we poured each liquid into a large graduated cylinder, with the denser liquids on the bottom. The less dense liquids floated on the denser liquids. We could easily distinguish one liquid from another, because they did not mix.

Most of the time, solids, such as pennies, have higher densities than liquids and gases. Since a solid has very little space in between its particles, its density is usually higher than a liquid's density. A solid has a fixed volume and shape, so its particles have strong forces keeping them together. Liquids have particles that are slightly further apart than they are in a solid, so their density is slightly lower. A liquid has a fixed volume, but has a shape that varies, which allows it to flow. The forces that keep liquid and solid particles together are very weak in gases. A gas has a volume and shape that varies, so it can freely move in a room. These conclusions extend our knowledge and are proven with everyday occurrences. This experiment was a success, since we found out that there truly is a difference between the pre-1982 pennies and the post 1982 pennies.