Chemistry 111

May 16, 2013

Density Lab

Purpose:

The objective of this experiment is to learn how to use basic laboratory equipment, such as the buret and analytical balance. We will learn how to calculate the density two different ways. First we will calculate the density using dimensional analysis with a ruler. Then we will calculate the density using volumetric conversions.

Methods

Part 1:

Before you begin this part of the experiment, make sure your buret is clean and functional. Next you use the analytical balance to weigh your 50mL beaker. Make sure to tare the balance prior to placing the flask on it. Make sure that the doors are closed whenever you tare the analytical balance. Next we fill the buret with DI water up past the zero mark. Drain the water out until the bottom of the meniscus is at the zero mark. After this is completed deliver 24.00 mL of DI water from the buret to the beaker and record this volume. Next weigh the beaker plus water and record the mass. Dry your 50 mL beaker and repeat the process with tap water. After repeating this process calculate the density of tap water and DI water. Compare the density of DI water and tap water.

Part 2:

For the first method of calculating density you use dimensional analysis using a ruler. Measure the appropriate dimensions of the rubber stopper in centimeters using the ruler. Measure the height of the stopper, the small radius, and large radius. Make sure to record all readings with the appropriate unit, “cm”. Next sketch the rubber stopper in your laboratory notebook and show where the measurements were made. The volume of the rubber stopper is calculated using this equation: V=(πh/3)(R2 + Rr + r2). The small radius is lower case r, the large radius of the stopper is uppercase R, and the height is h. Next use the top-loader balance to find the mass of the rubber stopper. Make sure to tare the balance before placing the object on it. Write the measured mass in your lab notebook. Then find the density and record that in your notebook.

The second way to determine the volume is to measure the volume of water displaced. You will use a graduated cylinder filled to the 50.00 mL mark. Then drop the rubber stopper in the cylinder being careful not to splash any water or your calculation will be wrong. The volume can then be found by the differences in the volumes of water before and after the rubber stopper was added. Use the mass determined before. Now compare the densities of the…