JCE Classroom Activity: #64
Instructor Information
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Bowling for Density!
Kathleen Holley, Diana Mason, * and Kirk Hunter Department of Chemistry, University of North Texas, Denton, TX 76203; *
[email protected] 2 Department of Chemical Technology, Texas State Technical College, Waco, TX 76705 In this open-ended inquiry Activity, students predict whether a given bowling ball will float or sink in tap water based on measurements of radius and weight to determine the density. Students gain practice in measurement techniques as well as calculations involving unit conversions and geometric formulae. 1
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Bowling balls are commonly constructed of synthetic and metallic materials and covered with polyester or polyurethane (1). Recent developments in bowling ball coverstocks include “reactive resin” and “particle technology”, but professional bowlers are the primary users of these expensive balls. The interior components of most bowling balls are proprietary, so it is difficult to accurately calculate a theoretical density for a bowling ball. According to the World Tenpin Bowling Association, the maximum circumference for a competition bowling ball is 27 in.; maximum weight is 16 lbs. (2). This gives a maximum calculated density of 1.32–1.36 g/cm3, depending on finger hole size and whether or not their volume is subtracted from the calculated volume. Heavier bowling balls produce more force to knock down pins. Larger bowling balls permit more lateral motion through rotational effects; bowlers use this “hook” to approach the pins at angles that cannot be produced by rolling the ball down the alley in a straight line (1, 3). Most bowlers favor larger diameter spheres with no more weight than they can comfortably swing (3). Many smaller-weight bowling balls have a density less than 1.00 g/cm3 and float in water. This result surprises students, especially those who confuse the concepts of density and weight and assume that all large, solid objects will sink in water.
This Activity could be used in curriculum units dealing with measurement, unit conversions, significant figures, or physical properties of matter such as density.
perforated
About the Activity
photo by Diana S. Mason
Integrating the Activity into Your Curriculum
One bowling ball for every 3–4 students is recommended. Students design a procedure to calculate the density of their ball and predict if it will float or sink in tap water. They make measurements with available tools, but do not place the ball into water until after making their prediction. A sample student procedure and data table are in this issue of JCE Online.W Consider these issues: Should available measuring tools be placed where students can see them before they develop their procedures? Should all groups develop a procedure before any group begins testing, so a group doesn’t write a procedure based on observing another group? Materials are usually available at no cost or are found in the home. Bowling alleys may donate used balls or balls may be available at thrift stores or rummage sales. Household-measuring equipment (e.g., plastic or fabric tape measures, string and rulers, bathroom scales, etc.) is appropriate. Graduated cylinders should be available for students to determine the volume of the finger holes, although this only slightly affects the calculated density (see Question 3). Students will need unit conversion factors to calculate the density of the ball in g/cm3 and may need the formula for the volume of a sphere and values for density of water, or they can look these up. Significant digits will depend on the measuring devices. A trash can makes an excellent “testing tank”. Determine that the opening is large enough for a ball (∼10 in./∼25 cm), and the container is deep enough to allow a ball to float. Fill the can about 3/4 full of water, enough to cover a bowling ball that sinks. Prevent spills by leaving the filled trash can in a water trap such as a large sink.
Answers to Questions
This Classroom Activity may be reproduced for use in the subscriber’s classroom.
fold here and tear out
Background
1. The density of the solid compared to the density of the liquid determines whether the solid will float or sink. The density of tap water is ∼1 g/cm3. Solids with densities less than 1 g/cm3 float, greater than 1 g/cm3 sink. 2. Students might measure the circumference of the ball to calculate radius and volume (C = 2r, V = 4/3r3). 3. Correcting for finger hole volume will change the calculated density, usually by less than 5%. 4. Inaccurate measurements for circumference and weight are possible answers. (How accurate is a bathroom scale for measuring smaller weights? Was a measuring tape passed around the actual circumference?) 5. The density of water varies with temperature (0.997 g/cm3 at 25 ⬚C; 0.962 g/cm3 at 100 ⬚C), which could affect whether the ball floats or sinks. However, students will probably be using room temperature water.
References, Resources, and Related Activities (accessed Jul 2004) 1. McCorvey’s Pro Shop: Everything You Need To Know About Buying a Bowling Ball but Were Afraid to Ask. http://www.alabamabowling.com/mccorvey/balltalk.shtml 2. Dimensions for Bowling. http://www.topendsports.com/sport/tenpin/dimensions.htm 3. Use the Force. http://www.epinions.com/content_1202495620 JCE Classroom Activities are edited by Erica K. Jacobsen
www.JCE.DivCHED.org
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Vol. 81 No. 9 September 2004
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Journal of Chemical Education
1312A
JCE Classroom Activity: #64
Student Activity
Bowling for Density! Physical properties of matter are central to describing how different substances will behave in the real world. Will a large, solid object such as a bowling ball float or sink in tap water? It’s your job to find out—but without placing the ball in water first! What physical properties of a bowling ball would help determine whether it will float or sink? How could you measure those properties to obtain the data you need to do calculations to make a prediction of sink or float?
Try This
__1. Write out your procedure with enough detail so that someone else could accurately repeat your experiment without any other information from you. __2. Set up a data table or other suitable organizational system for your experimental data. __3. Follow your procedure and collect data as specified. __4. Make any necessary calculations and report your results. __5. Based on your calculations, predict whether the ball will float or sink in tap water. __6. Show your instructor your work. If it is acceptable, you will be able to test your prediction by placing your bowling ball into a large container of tap water to directly observe whether it floats or sinks. __7. Record the result of the water test from step 6. Compare the result to your prediction from step 5.
photo by Diana S. Mason
You will need: a bowling ball, measuring tools of your choice and/or those provided by your instructor, and a calculator. If you are curious about the sport of bowling you might find the Web references below of interest. Design a procedure and collect data to calculate whether your bowling ball will float or sink when placed in tap water. Do NOT place your bowling ball in water until you have designed, written, and carried out your procedure and shown your procedure, calculations, and prediction to your instructor. Be Safe! Bowling balls are heavy and roll easily, so watch your fingers and toes! If you place a bowling ball on a counter or desk, you must secure the ball in some way so that it cannot roll off the edge. Do not loft or roll the balls.
More Things To Try You might like to repeat the steps above with other common spherical objects, such as golf balls or marbles.
Questions 1. What property of a solid determines whether it will float or sink in a liquid? What value of that property determines whether a solid will float in tap water? 2. What did you measure in order to determine the volume of the bowling ball? 3. Does subtracting the volume of the finger holes from the calculated volume of the spherical ball change the calculated density? If it does, by what percentage? 4. Identify at least two possible sources of error. Explain your answers. 5. Would the temperature of the water make a difference as to whether the ball sinks or floats? Why or why not?
Information from the World Wide Web (accessed Jul 2004) 1. McCorvey’s Pro Shop: Everything You Need To Know About Buying a Bowling Ball but Were Afraid to Ask. http://www.alabamabowling.com/mccorvey/balltalk.shtml 2. Dimensions for Bowling. http://www.topendsports.com/sport/tenpin/dimensions.htm 3. Use the Force. http://www.epinions.com/content_1202495620
This Classroom Activity may be reproduced for use in the subscriber’s classroom.
1312B
Journal of Chemical Education
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Vol. 81 No. 9 September 2004
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www.JCE.DivCHED.org
