# Golf Ball Lab - PowerPoint by niusheng11

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```									     Golf Ball Lab

What is the minimum amount of salt
needed to make a golf ball float?
Determine the minimum amount of salt needed
to make a golf ball float in 100 mL water.

Weigh out 50.0 g of NaCl
Add 5 g additions of salt to the water, dissolve, check to see if ball floats.
Continue with this method of successive additions until ball floats.
Re-weigh remaining salt and subtract this amount from 50.0 g to determine
the amount of salt needed.
Finally, repeat…begin 5 g less salt and add 1 g increments to narrow range.

Trial          Salt (g)            Total         Float /Sink
1              5.0 g             5.0 g             Sink
2              5.0 g            10.0 g             Sink
3              5.0 g            15.0 g             Sink
4              5.0 g            20.0 g             Sink
5              5.0 g            25.0 g            Float
Theorize, but Verify
…We must trust in nothing but
facts. These are presented to us
by nature and cannot deceive. We
ought in every instance to submit
our reasoning to the test
of experiment. It is especially
necessary to guard against the
extravagances of imagination which
incline to step beyond the bounds
of truth.

Antoine Laurent Lavoisier, 1743 - 1794

Jaffe, New World of Chemistry, 1955, page 1
Theory Guides, Laboratory Decides!
Density of water = 1.0 g/mL

Need to determine density of a golf ball.
mass =______ g (electronic balance)
volume = ______ mL (water displacement method) or formula?

Density of golf ball cannot be made to decrease. Therefore, you need to
increase the density of the water by dissolving salt into the water.

Limiting Factor: accurate determination of volume of golf ball

Solubility Curve of salt in water.
Water has a limit to how much salt can be dissolved.
Saturation – point at which the solution is full and cannot hold anymore solute.
Packing of NaCl Ions

Electron Microscope
Photograph of NaCl
Dissolving of Salt in Water

Na+
ions                   Water molecules

Cl-
ions

NaCl(s) + H2O  Na+(aq) + Cl-(aq)
Dissolving of NaCl
H         H

O

Na+

+                                     +
+
hydrated ions
-      +        -                               +   -
+      -                                       -
Cl-

Timberlake, Chemistry 7th Edition, page 287
Interstitial Spaces and Particle Size

Interstitial spaces
(holes in water where substances dissolve)

100 mL
Easy
Parking at school if you arrive at 7:00 AM = _____
Hard
Parking at school if you arrive at 7:45 AM = _____

More available spaces if you arrive early. Salt dissolves quicker when you
begin because there are more available spaces to 'park'.

Analogy: Compact car is easier to park than SUV.
Theory: Crush salt to make particles smaller (increase surface area)
…it will dissolve more rapidly.                                        STIR
100 mL of water = 100 g        density of water= 1.00 g/mL

You determine the density of golf ball to be 1.18 g/mL

Add 19 g salt to 100 g water = 119 g salt + water
Volume remains100 mL (saltwater)

Density =     Mass                    119 g
volume         or       100 mL

Density (saltwater) = 1.19 g/mL

If golf ball doesn’t float, add 2 g additions of salt until it floats.

Add 3.0 mL water,stir…float                  119 g      x g salt
100 mL  6 mL 100 mL
Goals and Objectives:
a. Given materials and problem, formulate and test a hypothesis to
determine if a golf ball can float in salt water.
b. Collect accurate data and compare own data to other class
data. Evaluate own results.

Investigation Procedure:
a. Design an experiment to accurately determine how dense salt water
must be in order for a golf ball to float. Use metric units. Be sure to
control as many variables as possible.
b. Write down the procedure that you and your partner(s) are going to use
prior to lab day. Record any researched facts that may be useful in
c. Carefully run your experiment, make observations and record your
measurements in a data table. Use grams and milliliters in your
measurements. Include a calculation column in your data table.
another group, then modify your own steps as needed.
e. Repeat your experiment to check for accuracy, if time allows.
Discussion Questions for Understanding:

a. How did you determine the density of your golf ball?
b. Why does a golf ball normally sink to the bottom of a pond at the golf course?
c. What variables were difficult or impossible for you to control during this
experiment?
How much salt can be dissolved in 100 mL of water? (saturated)
effect of temperature on solubility
Surface area of salt may affect rate of dissolving (may need to crush salt finely)
d. What variables may have changed as time went on that could have affected
e. Did you improve the accuracy of your results after conferring with another
group?
f. Describe your sources of error.
(Human error and faulty equipment are unacceptable answers)
Materials:
electronic balance                  100 mL & 500 mL graduated cylinder
mortar / pestle                     glass stirring rod
golf ball                           salt (Kosher, iodized table salt, table salt)
250 mL beaker
Extension:
a. Research the manufacturing of golf balls to determine why they sink in
pond water.
b. Research to determine which body of salt water in the world would float a
golf ball the highest.
Lab Report : (10 - 12 point font two page maximum length)
Background / problem
Hypothesis (if...then)
Procedure (protocol)
Data (table, graph)
Analysis
Conclusions / Future directions (limitations)
Sample calculations - appendix

Do not use references to yourself or others in your writing of a lab report
(except for citing past research).
OR
Poster (25 words or less) A picture is worth 1000 words!
Solubility vs. Temperature for Solids
140
KI
130

120

110              NaNO3                  gases

Solubility

Solubility (grams of solute/100 g H2O)
solids
100
KNO3

Table                                                                                                             90

80
HCl               NH4Cl
shows the dependence                                                                                               70

of solubility on temperature                                                                                          60              NH3                    KCl
50

40

30
NaCl     KClO3
20

10
SO2

0   10 20 30 40 50 60 70 80 90 100
LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 517
Teacher Notes
Some golf balls will NOT float in a saturated solution of salt water.
Their mass is too great.
The maximum density of salt water is ~1.36 g/mL. The solution is saturated.

The limiting factor is determining an accurate volume for the golf ball.
My students use a 250 mL graduated cylinder.
Anything smaller and the golf ball won’t fit.
Each line is 5 mL (students often think it goes by 10 mL increments).

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