Today, we performed a minilab in which we tried to find the composition of small BB’s in a container. We took the mass of a graduated cylinder filled with 20 ml of water, and then massed the same cylinder with a volume of BB’s equal to 5 ml, 10 ml, and then finally, 15 ml. We then subtracted the mass of the cylinder and water to get the masses of the BB’s. Here are the masses my group had, along with the calculated masses of the BB’s by themselves:
1. Grad. Cyl.+20mL water: 66.12g
2. G.C.+20mL+ 5mL BB’s: 107.29g
3. G.C.+20mL+10mL BB’s: 146.24g
4. G.C.+20mL+15mL BB’s: 184.49g
1. 41.17g of BB’s.
2. 80.12g of BB’s.
3. 118.37g of BB’s.
It was here when we were subsequently told of how imprecise measurements are, especially with equipment in which you must eye the measurement like with tripe-beam balances, how a number such as 146.24 is not equal to and is less precise than 146.240, and that a greater number of zeros at the end of a number with a decimal means greater precision.
Anyways, from my data, I concluded that the BB’s are most likely composed of a copper and zinc alloy in an approximately 50:50 proportion. I include my group’s average density of the BB’s, 8.012 g/cm3, and the density of copper and zinc at about a 50:50 ratio, which is about 8.03 g/cm3, as evidence. Our data is reliable to the nearest hundredth of a gram, which is the most precise decimal point our balances could go to. Additionally, one rule of significant-digit calculation requires the produce to have at most the number of significant digits as the number with the least digits, which I have followed. Therefore, I can conclude that my data and my calculations are reliable and valid.