Chemistry Density Lab

Density Lab

INTRODUCTION

All substances have characteristic properties that we can use to identify them. A characteristic

property is independent of the sample size, and depends only on the nature of the substance. The

two basic types of properties associated with matter are chemical properties and physical

properties. A useful tool in the identification of unknown substances is the comparison of

characteristic properties of the unknown substance with known substances. By comparing a few

properties of an unknown substance to properties of a known substance we can narrow down the

identity of the unknown. The more of these properties we know, the better we can determine the

identity the substance.

Density is a physical property that is easy to calculate by measuring two properties: mass and

volume. All matter takes up space and has mass. Density represents the ratio between the mass

of a sample and its volume. Density is independent of the size of the sample however it does

depend on the temperature of the sample. This means that the density is constant for a substance

as long as the temperature is the same. Substances expand and contract with changes in

temperature, which in turn affects the space occupied, or volume.

The calculate measurement of density is the one of the easiest of laboratory procedures. In this

lab, you will determine the density of irregularly shaped solid samples by measuring the mass

and volume of a sample of the substance. A balance will be used to determine the mass of the

sample. The volume of the irregularly shaped object will be determined by the measuring the

displacement of water. Once the mass and volume have been measured, density will be

calculated using the following relationship:

Density = !”## %& ‘(“!#

)*+,!- %& !.

Density Activity:

In this lab you will be measuring the volume of an irregularly shaped object with a known

mass. From the experimental data, density will be calculated.

Prepare your notebook. When the lab is complete your lab notebook should include the

following:

1. Include Density Lab in the Table of Contents

2. Write the title of the lab on the top of the page.

3. Date/number the page (if you work on it over a few days, date each time you are

working). Sign in your lab notebook each time you stop working.

4. Record the Purpose of Experiment in your own words. Remember the purpose is the

overall question that will be answered by collecting the data and doing any

requested calculations.

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5. Indicate PPE (personal protection equipment) required while performing the lab:

goggles, closed-toed shoes

6. Complete the pre-lab questions below. Record ANSWERS ONLY in your notebook.

7. Copy Table 1 found in the Procedure in your notebook. Leave enough space to

record your data.

8. Complete the Post-lab questions. Record ANSWERS ONLY in your notebook.

Pre-lab Questions

Q1: What two physical properties will you measure in order to calculate the density?

Q2: What are the common units for density?

Q3: A solid piece of metal weighing 14.8 g is added to 25.0 mL of water in a graduated

cylinder. The water level rises to 26.9 mL. Calculate the density of the metal. Show your

work.

Procedure:

Remember to make all measurements to the correct precision

Materials needed:

Pre-massed bolt

Graduated cylinder appropriate for your sample size

The purpose of this experiment is to investigate different ways of calculating density and to

continue to practice making measurements to the correct precision.

A. Measuring Volume of an Irregularly shaped object (a bolt)

1. Obtain the pre-mass bolt from your lab kit.

2. Record the description (color, length) of the bolt on the data table.

3. Record the mass of the solid, found on the L02 bag, in grams, on the data table.

4. Choose the smallest graduated cylinder that is appropriate for your bolt’s size.

Which size? The sample must fit into the cylinder, and be completely submerged in

water, without going above the markings.

5. Fill the empty graduated cylinder about half-full with water. Measure the starting

volume of water using the correct precision. Record the volume as the initial

volume in the data table.

6. Carefully add the bolt to the cylinder. Measure the volume of the water after the

bolt is added using the correct precision. Record the volume as the final volume in

the data table.

7. Collect two more data sets from other students in the class. The new sample should

be the same metal, however it may not have the same mass and volume as your trial.

8. Dry the wet bolt with a paper towel and return to kit.

9. You may share your data with your group. If you are not in a group, post your data

in the Density Lab discussion board so you can exchange data with other students.

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Table 1.

Description of solid sample 1:

Description of solid sample 2:

from student 2

Description of solid sample 3:

from student 3

Mass of bolt 1: Mass of bolt 2: Mass of bolt 3:

Initial volume, V1 Initial volume, V1 Initial volume, V1

Final volume, V2 Final volume, V2 Final volume, V2

Volume displaced, Vd Volume displaced, Vd Volume displaced, Vd

Volume of solid, Vs Volume of solid, Vs Volume of solid, Vs

Calculated density Calculated density Calculated density

Average density

Calculations:

1. Calculate the volume of the water displaced, Vd, by subtracting the initial volume, V1,

from the final volume, V2.

2. The volume of the water displaced, Vd, is equal to the volume of the solid, Vs.

3. Calculate the density of the solid sample and record the value in the data table.

𝑫𝒆𝒏𝒔𝒊𝒕𝒚 =

𝒎𝒂𝒔𝒔 𝒐𝒇 𝒕𝒉𝒆 𝒔𝒐𝒍𝒊𝒅

𝒗𝒐𝒍𝒖𝒎𝒆 𝒐𝒇 𝒕𝒉𝒆 𝒔𝒐𝒍𝒊𝒅

4. Calculate the average density

𝑨𝒗𝒆𝒓𝒂𝒈𝒆 𝒅𝒆𝒏𝒔𝒊𝒕𝒚 =

(𝒅𝒆𝒏𝒔𝒊𝒕𝒚𝟏 + 𝒅𝒆𝒏𝒔𝒊𝒕𝒚𝟐 + 𝒅𝒆𝒏𝒔𝒊𝒕𝒚𝟑)

𝟑

Post-Lab questions

Answer the following questions in your lab notebook

1. Explain why the solid sample sinks in water.

2. Suppose you were asked with a partner to determine the density of rubber. To do

this, you cut a rubber stopper into two pieces, and each partner determined the

density of their piece. Which of the following would be the best way to report your

answer? Explain your choice. (1) Report your experimentally determined density

as the density of the stopper, (2) Add the density you determined to the density

your partner determined and report the total density, or (3) average both values of

the density and report the average of the two densities.

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3. An important part of the experimental process is error analysis. We need to identify

errors in our measurements to determine how they affect our conclusions. The

following are errors that were made while performing a density experiment.

a. You used the displacement of water to determine the volume of a solid

sample. When the final volume was measured, the water did not completely

cover the solid, so some of the solid was sticking out of the water. (1) Would

the volume recorded for the solid be too high or too low? (2) Would the

error cause your density calculated for the solid to be higher or lower than

the actual density? Explain.

b. As you dropped the solid into the water to measure its volume, water

splashed out of the container. (1) Would the volume recorded of the solid be

too high or too low? (2) Would the error cause the density calculated for the

solid to be higher or lower than the actual density? Explain.

4. What is the volume, in liters, of 57g of alcohol, if the density is 0.780 g/mL?

5. Given the densities of the following liquids and solids, draw a test tube showing the

position of each substance if you were to layer them in the test tube.

Substance Density (g/mL)

water 1.00

mercury 13.6

vegetable oil 0.93

cork 0.24

silver ring 10.5

rubbing alcohol 0.78

Works cited: Mullins, N.J., & Milczanowski, S.E. (2020). Lab Manual for Introductory Chemistry

CHM1025C/CHM1032C. Jacksonville: FSCJ Copy Center.