3.2: Lab - Density of Solids and Liquids

Laboratory Preparation Guide

Equipment and Materials

Prepare 12 sets of equipment and materials for 24 students per class section. Include a few more for backup if needed. Each set should include

Equipment

• One (1) 100 mL graduated cylinders
• One (1) 2000 mL graduated cylinders
• MiniOmni Sonometer

Materials

• One (1) metal piece per set. Alternate aluminum, copper, and zinc between the sets.
• One (1) piece of Dentley’s bone (purchased from PETCO)
• One (1) piece of Boss bone (purchased from PETCO)
• Distilled water (students use from distilled water container in room)

Note: The metals should not have any other metals screwed in or strings attached

Set-up Guide MiniOmni Bone Sonometer

Please faculty spend 10 minutes to watch the video links to learn how to use the sonometer.

1. Unboxing:

2. Connecting the unit to laptop:

3. Calibration:

4. Take a patient scan:

5. Sample Results:

Learning Objectives

• Recognize density as an intrinsic property
• Determine mass and volume of a substance and calculate its density
• Determine bone density and use it to predict bone health (osteoporosis)

Laboratory Skill

• Practice using electronic balance
• Practice reading measurements in graduated cylinder
• Practice using graphical data to solve problems

Equipment and Materials

• 50 mL or 100 mL graduated cylinders
• Metal pieces (e.g., aluminum, copper, and zinc)
• Bones
• Distilled water

Safety and Hazard Information

N/A

Background Information

Density

Every substance has a unique density, which distinguishes it from other substances. For example, the density of a patient’s bone can be measured and used by clinicians to determine bone health, risk for bone fractures, and diagnosis of the medical condition called osteoporosis. Osteoporosis occurs when the body loses too much bone or makes too little bone. The bone becomes porous and loses it strength. People with osteoporosis can easily suffer from fractures. Clinicians can use a bone density scanner device like the BeamMed’s MiniOmni Bone Sonometer to determine bone health. The Sonometer reports bone health in terms of T-score. A T-score greater than -1 SD implies healthy bone. A T-score range of -1 to -2.5 SD indicates low bone density (Osteopenia). A T-score lower than -2.5 SD is an indication of significant loss of bone density (Osteoporosis). In other words, a T score is a standard deviation, that tells you how your bone density test scores varies from the mean score of a 30 year old healthy bone.

Density has been used to determine the purity of precious metals such as gold. The density of gold is 19.3 g/mL. In general, items sold as “made out of gold” are not usually pure in gold. For example, a gold ring is not usually entirely gold, but a mixture of gold and some less expensive metal. In its physical appearance it is difficult to distinguish between an item that is composed of pure gold and one that is composed of a mixture of gold and a cheaper substance. Many people easily confuse fool’s gold with gold. Fool’s gold is a mineral that is composed of iron sulfide (\(\ce{FeS2}\)), with a luster like that of gold (\(\ce{Au}\)). The density of fool’s gold is about 4.9 g/mL - quite different from the density of gold. Density can therefore be used to distinguish between gold and fool’s gold.

Density is a physical property that relates the mass of a substance to its volume. In simple terms, density is defined as the mass per unit volume of a substance, represented by Equation \ref{1}:

\[\text{Density } = \frac{\text{Mass in grams (g)}}{\text{Volume in milliliters (mL)} } \label{1}\]

The densities of solids and liquids are expressed as g/mL or g/cm\(^3\). For gases the g/L unit is favored since their densities are usually smaller. When a substance has a density less than that of water (1.00 g/mL) it will float and when the density is greater than the density of water, it will sink.

Density of Liquid

Density can be determined in the laboratory by measuring the mass and volume of a substance. To measure the density of a liquid, first measure the mass of a clean, dry beaker. Then add the liquid and find the combined mass of the beaker and liquid. Subtract the mass of beaker from combined mass to determine the mass of the liquid. Measure the volume of the liquid by placing it in a graduated cylinder and using the proper technique to read its volume (Figure \(\PageIndex{1}\)).

Figure \(\PageIndex{1}\): Read the volume of a liquid at eye-level and at the bottom of the meniscus

Density of Solid

The volume displacement method, shown in Figure \(\PageIndex{2}\), is one common technique used to measure the volume of solids. Typically, this involves placing and measuring the volume of water in a measuring cylinder of appropriate size. This is followed by plunging the solid object in the water and observing the differential volume caused by the object (i.e., the displaced volume). Subtract the initial volume measurement from the final volume measurement to obtain the volume of the submerged solid.

Figure \(\PageIndex{2}\): Volume Displacement Method

The densities of some common metals, including bone, are provided in Table \(\PageIndex{1}\).

Table \(\PageIndex{1}\): Density of common substances

Substance	Density (g/mL)	Substance	Density (g/mL)
Aluminum	2.7	Lead	11.3
Brass	8.4	Zinc	7.1
Copper	8.9	Cork	0.26
Tin	7.3	Silver	10.5
Bone	1.80	Rhodium	12.4
Iron	7.9	Platinum	21.45

In this experiment, students will use density to identify or ascertain different metals. The density of water will also be determined.

In a clinical setting, a scanner is used to determine the density of bones. Bone density is used to predict bone health (osteoporosis). In this experiment, the use of the BeamMed’s MiniOmni Bone Sonometer to determine bone density will be optional.

Special Instructions (if any)

Retain all solid samples in this experiment for reuse.

Procedure

\(\PageIndex{A}\): Density of Metal

We will use the water displacement method to determine the density of a metal object.

1. Obtain a metal object and record its name or chemical symbol on Table \(\PageIndex{2}\) in the experimental report.

2. Weigh the metal and record its mass.

3. Use the volume displacement method to measure its volume.

4. Calculate the volume of the object and record it.

5. Calculate the density of object and record it.

6. Refer to Table \(\PageIndex{1}\) to compare your determined density with the literature value. Is your determined density similar or different?

\(\PageIndex{B}\): Density of Liquid

1. Obtain a sample of distilled water (any quantity of your choice) and determine its mass and volume. Record your data on Table \(\PageIndex{3}\) in the experimental report

2. Calculate the density of the water sample using Equation \ref{1}.

\(\PageIndex{C}\): Density of Bones

Here your instructor may ask for a volunteer who is willing to be scanned. This is optional!

1. Watch the video on how to collect bone density using the MiniOmni Bone Sonometer:

2. Collect the bone density (T-score) for the volunteer.

3. Record your data on Table \(\PageIndex{4}\) in the experimental report.

4. Use your T-score data to determine the health of each bone. Watch the measurement report video to interpret the results:

Experimental Report

\(\PageIndex{A}\): Density of metal

Table \(\PageIndex{2}\): Mass and volume measurements of metal sample

Name of metal (or chemical symbol)	Mass of metal (g)	Initial water volume (mL)	Final water volume (mL)	Volume of metal (mL)

Calculate the density of your metal. Show all work.

State if your determined density is similar or different from expected value (Refer to Table \(\PageIndex{1}\)).

\(\PageIndex{B}\): Density Liquid

Table \(\PageIndex{3}\): Mass and volume measurements of liquid sample

Name of liquid	Mass of water (g)	Volume of water (mL)
Water

Calculate the density of liquid sample. Show all work.

The density of water at 4\(^{\circ}\)C is 1.00 g/mL. Your determined density above may be slightly different; what is a possible reason for the difference?

\(\PageIndex{C}\): Density of Bone

Table \(\PageIndex{4}\): Patient Bone Density Data from BeamMed’s MiniOmni Bone Sonometer

Volunteer	T-Score	Diagnosis

1. Bone density can be used as an indication of bone health or bone strength. Compare your determined bone densities with that of a healthy bone reported in Table \(\PageIndex{1}\).

a. State if the volunteer’s bone is healthy and why.

Post Lab Questions

Exercise \(\PageIndex{1}\)

Mercury is a unique metal in that is highly toxic, especially to children and is a liquid and room temperature. A GGC student pours 33.8 mL of mercury into a graduated cylinder. The electronic balance reads 459.0 g for the poured amount. Determine the density of mercury.

Exercise \(\PageIndex{2}\)

Assume that the density of a precious metal that is used to pivot a broken bone is 10.5 g/cm\(^3\). A surgent has 43.2 g of this metal in stock. What is its volume in mL?

Exercise \(\PageIndex{3}\)

A dual-energy x-ray absorptiometry (DEXA) is used in many hospitals to measure the bone mineral density (BMD) of patients. Healthcare officials can then use the BMD values to predict the risk of fracture or bone disease by determining a T-Score using the formula below:

\[T - \text{ score } = \frac{ (\text{Average BMD } - \text{ Reference BMD})}{\text{Standard Deviation}}\]

Using your knowledge of excel and density concepts discussed in this lab, classify the patients described in the table below as osteoporotic, at risk of fracture or healthy.

Table \(\PageIndex{2}\): DEXA Patient data. The reference BMD value for a health bone is 942 mg/cm\(^{2}\)

	Patient A	Patient B	Patient C	Patient D
Age	BMD (mg/cm\(^2\))	BMD (mg/cm\(^2\))	BMD (mg/cm\(^2\))	BMD (mg/cm\(^2\))
25	790	1055	1040	1189
35	705	1038	1017	1141
45	700	1002	1034	1094
55	706	990	973	1072
65	549	969	930	1027
75	530	928	900	1024
85	479	859	703	933
Average BMD
Standard Deviations
T-score

Discuss your diagnosis below and show your work.