Materials Included In Kit

Additional Materials Required

Prelab Preparation

This lab is designed as a seven-station lab—student groups determine the density of one material at each of the seven stations. The lab can be easily modified to include more or fewer stations, depending on your needs.

Set up seven lab tables or stations by placing the following items on each table prior to the lab. Balances can be placed in a central location and shared, if enough are not available. For introductory classes, instruction cards (provided as half sheets in the Teacher PDF) can be copied, laminated (if desired) and placed at each station. A data table is provided in the Student PDF. For higher level classes, you may decide not to use the instruction cards or the data tables. Advanced students can write their own procedure and make their own data tables.

Station 1—Clear Liquid I (Distilled Water)
Water, distilled, 150 mL
Balance
Beaker, 250-mL (to hold distilled water)
Graduated cylinders, 100-mL, 2
Paper towels

Station 2—Clear Liquid II (Mineral Oil)
Mineral oil, 20 mL
Balance 
Beaker, 100-mL (to hold mineral oil)
Graduated cylinders, 10-mL, 2
Paper towels 
Pipets, 2

Station 3—White Block
Balance 
Metric rulers, 2 
White blocks, 2
 
Station 4—Foam Block
Balance
Foam blocks, 2
Metric rulers, 2

Station 5—Rubber Stopper
Tap water 
Balance
Graduated cylinders, 100-mL, 2 
Paper towels
Rubber stoppers, 2

Station 6—Glass Sphere
Balance
Beaker or cup (to hold spheres)
Glass spheres, 2
Metric rulers, 2

Station 7—Metal Cylinder
Tap water 
Balance
Graduated cylinders, 100-mL, 2 
Metal cylinders, 2
Metric rulers, 2
Paper towels

Safety Precautions

Although the materials in this lab are not considered hazardous, follow all standard laboratory safety procedures.

Disposal

All materials in this kit can be saved and reused.

Teacher Tips

• This kit is designed as a seven-station lab in which each lab table is set up as outlined in the Prelab Preparation. Enough materials are provided so that two groups of two can work at eact station. This setup is ideal for 28 students working in pairs (14 groups of students); however, it can be easily modified to fit your laboratory situation.
• Student groups move from station to station and determine the density of the particular material at each station until all seven stations are complete. Encourage students to only gather data at the stations and do further calculations of volume or density at their desks after data collection. This helps to keep the groups moving efficiently from station to station.
• If your preference is to have students determine the density of all seven materials at their own lab tables (without moving from station to station), multiple density lab kits can be purchased. One kit is needed for each group of four students (two groups of two).
• Encourage students to read and record each measurement as precisely as the measuring instrument allows. This is a good opportunity to teach and/or reinforce the use of significant digits in calculations.

Answers to Prelab Questions

Sample Data

Actual student data may vary from the data provided.

Answers to Questions

1. Rank the materials tested in this lab in order from most dense to least dense.
   Aluminum cylinder, glass sphere, rubber stopper, water, mineral oil, white block, foam block.
2. If the foam block was cut in half, would the density change? Explain.
   No, the density of the block would not change if it were cut in half since density is an intrinsic physical property and does not depend on sample size.
3. List the items in this lab that would float on water. How was this determined?
   Mineral oil, the white block, and the foam block would float on water since their densities are less than the density of water, which is 1.0 g/mL.
4. Consider the following six materials—water, mercury, mineral oil, cork stopper, rubber stopper, and a piece of lead. If these materials were added to a graduated cylinder, in what order would they be found from top to bottom?
   From top to bottom, the materials would be in the following order—cork, mineral oil, water, rubber, lead, mercury.
5. Why is density an important factor to know about a material?
   Density is an important factor since it is a property unique to each substance and can help to determine the identity of the substance.
6. Use the Table of Densities of Common Substances to identify Clear Liquids I and II.
   Clear Liquid I is water (distilled) and Clear Liquid II is mineral oil.
7. Observe the metal cylinder tested in station 7. Using the density you obtained and observations, identify the metal.
   Aluminum metal.
8. From your answer to Question 7, which method for determining density did you find to be more accurate? Explain.
   In the sample data provided, measuring volume with a ruler was found to be more accurate than using the water displacement method. (Student answers may vary depending on their data.)
9. Explain how you would find the density of your own body.
   Student answers will vary. Determine mass by finding your weight in grams. Then determine volume by water displacement. Density equals mass divided by volume.

Teacher Handouts

11969_Teacher1.pdf

Introduction

Why do some things float in water and others sink? Why do some balloons float in air and others do not? Investigate the important property of density by performing this laboratory experiment.

Concepts

• Mass
• Volume
• Density

Background

Density is defined as the amount of matter that occupies a given unit of space; it can also be thought of as the “compactness” of a substance. Dense materials (such as lead or gold) are very heavy for their size whereas less dense substances (such as a big bag of feathers or a filled balloon) are light for their size.

Density is equal to a substance’s mass per unit volume, where mass is the amount of matter in an object (measured in grams) and volume is the amount of space that an object occupies (measured in milliliters or cubic centimeters). The equation to calculate density is as follows:

Density is an intrinsic physical property of matter—that is, it is a property unique to a specific substance (at a specified temperature) no matter what size the sample. Density can therefore be used to distinguish one substance from another. The identity of an unknown substance can be determined by measuring its density in the lab. The experimental value for density can be compared to the density recorded in scientific literature and the substance can often be identified.

A substance’s density varies with temperature and pressure changes. The benchmark for comparing density is water which, at 4 °C, has a density of 1.0000 g/mL. Substances that float in water are less dense than water while substances that sink are more dense than water.

Determining the density of an object involves measuring the object’s mass and volume and then calculating the density. Mass can be measured using a balance. Volume can be measured several ways. The volume of a liquid substance can be measured using a graduated cylinder. When using a graduated cylinder, accuracy is important. The liquid volume should be read at eye level and at the lowest point of the meniscus (see Figure 1). The technique for measuring the volume of a solid, however, depends on the shape of the sample. For a regularly shaped solid—such as a cube, cylinder or sphere—the volume can be calculated using the appropriate equation from Table 1. The necessary quantities can be measured with a metric ruler. Note: π = 3.14 and r = radius = ½ d = ½ diameter of cylinder or sphere

The volume of an irregularly shaped solid, however, cannot be measured using a ruler; it must be found indirectly using a method called water displacement. Water displacement involves submerging the object into a known volume of water and measuring the volume rise after adding the object. The volume of water displaced by the solid is equal to the object’s volume (in mL or cm³).

Materials

Prelab Questions

Complete the prelab exercise before beginning the procedure.

Safety Precautions

Although the materials in this lab are not considered hazardous, follow all standard laboratory safety procedures.

Procedure

1. Determine the mass and volume of each of the following seven materials using the appropriate method as outlined in the background section.

   Station 1—Clear Liquid I
   Station 2—Clear Liquid II
   Station 3—White block
   Station 4—Foam block
   Station 5—Rubber stopper
   Station 6—Glass sphere
   Station 7—Metal cylinder

2. Record the mass and volume of each substance in the Density Data Table. Be sure to include the appropriate units.
3. Calculate the density of each material.
4. (Optional) Determine the identity of the metal cylinder by comparison with literature values for density.

Student Worksheet PDF

11969_Student1.pdf