INTRODUCTION TO QUANTITATIVE MEASUREMENT: DENSITY DETERMINATION

Introduction:

The study of chemistry involves not only observing changes in matter, but also measuring these changes. The techniques of data collection, data analysis, and measurement are an important part of chemistry. In conducting this experiment, you will make several mass and volume measurements and use these measurements to determine the density of water, an unknown liquid and an unknown solid. You will then determine the precision of your results by calculating percent error.

Density = Mass % error = Accepted value- experimental value x 100%

Volume accepted value

Safety Alert/MSDS:

Some liquids are harmful to the skin, do not spill or get on hands. Wash hands and rinse with plenty amounts of water.

Objectives:

1. Determine the density of different substances from mass and volume measurements.

2. Calculate the percent error in your results.

Materials List:

2 graduated cylinder (10mL and 100mL)

Balance

Beaker (100 or 250 mL)

String

Unknown liquid

Pre-Lab Questions:

Provide your answers to these questions on the last page within the Data Table.

a. Define density in your own words and give two everyday examples of instances of differing density.

b. Why is the accuracy of the laboratory balance that you use in this investigation important?

c. What effect would a less accurate balance have on your results?

d. Why should you avoid skin contact with the unknown solution?

e. How can the density of an unknown substance help you identify it?

Procedures:

A. Density of Water

a. Measure the mass of a 100 mL of 250 mL beaker to the nearest 0.1 g.

b. Use the balance to be sure you have added exactly 50 .00 grams of water to the beaker.

c. Pour the 50.00 grams of water into 100mL-graduated cylinder. Be sure to read the bottom of the meniscus as discussed in class. Record the volume to the nearest 0.5mL.

Chemistry Honors-laboratory #2

Name: ____________ Partner: ____________ Date: ____________ Period: ____________

Density of an Unknown Liquid

a. Measure the mass of a 10 mL graduated cylinder.

b. Fill the graduated cylinder to about the 9mL mark with the unknown liquid. Record the volume to the nearest 0.2mL.

c. Measure the mass of the cylinder and its contents carefully and record.

d. Return the unknown liquid to a container designated by your teacher.

Density of a Solid

a. Obtain a solid object from your teacher and measure its mass to the nearest 0.1g.

b. Fill a 100 mL graduated cylinder about one-half full of tap water and read the volume to the nearest 0.5mL.

c. Carefully immerse the solid in the water in the cylinder as shown in Figure 1-2. Record the new volume to the nearest 0.5mL.

d. Return the solid to a container designated by your teacher and pour the water into the sink.