Academic Chemistry BB density lab

Objectives Calculate density of BB’s Measure volume using the water displacement method Determine if a BB is solid copper by comparing its density to the known density of copper Construct graphs, determine equations for straight lines on the graphs, and gain an understanding of what these lines can be used for on a graph

Materials Electronic Balance, Graduated cylinder, BB’s, and Weigh boat

Background Using density to determine the identity of an unknown material has been done for many years. Because density is an intensive property, it does not change no matter how large the sample you have. In this lab students will attempt to determine if a BB is solid copper or not. They will do this by comparing the density that they find for their BB’s and the actual density of copper.

Procedure Place a weigh boat on the electronic balance and rezero the balance. Place 5 BB’s in the weight boat and record their mass Place approximately 5 ml of water in the 10 ml graduated cylinder and record its exact volume Place the 5 BB’s in the graduated cylinder and find the volume of just the BB’s (volume with BB’s – volume with no BB’s) and record Continue this process with 5 more BB’s until you have found the mass and volume of all 60 BB’s

Procedure Photos The weigh boat has a mass, however, we only want to record the mass the BB’s. A simple way to do this is by zeroing the balance by pushing the zero button. Once that is done, the balance will read zero, even though the weigh boat is on the balance. Adding 5 BB’s to the weigh boat measures just the mass of the 5 BB’s. Notice the weigh boat had a mass of 2.27 g and the 5 BB’s have a mass of just 1.70 g. Make sure you continue to add the masses of 5 BB’s together to get The mass of 10, 15, 20, etc

Procedure photos The volume of the graduated cylinder with no BB’s is about 5.1 ml. With BB’s, the water is displaced to a volume of 7.8 ml. Therefore the volume of this number of BB’s is 7.8 – 5.1 OR 2.7 ml

Data Collection & Analysis Measure the mass of each set of 5 BB’s until you have the mass of 60 total BB’s Measure the volume of each set of 5 BB’s until you have the volume of 60 total BB’s Calculate the density of each set of 5 BB’s Construct two graphs and determine the equation of each line (straight lines) Mass (y-axis) versus # of BB’s (x-axis) Mass (y-axis) versus volume (x-axis)

Grading Graphs are done correctly (labels, units, title, equation of line, etc.) 10 questions from back of data sheet