1. Golf Ball Lab What is the minimum amount of salt
needed to make a golf ball float?

2. 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
Sink 2
10.0 g 3
15.0 g 4
20.0 g 5
25.0 g
Float
(Comparison of salts.)

3. 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,
Graphic:
Unlike the Greeks, Lavoisier believed in experimental evidence to prove a point -- not just logic and reasoning.
Jaffe, New World of Chemistry, 1955, page 1

4. 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.

5. Packing of NaCl Ions Electron Microscope Photograph of NaCl
Sodium chloride is a cubic-shaped crystalline solid that has a melting point of 808oC.
Electron Microscope
Photograph of NaCl

6. Dissolving of Salt in Water
Cl-
ions
Na+
Water molecules
When sodium chloride crystals are dissolved in water, the polar water molecules exert attracting forces which weaken the ionic bonds. The process of solution occurs the ions of sodium and chloride become hydrated.
NaCl(s) + H2O  Na+(aq) + Cl-(aq)

7. Dissolving of NaCl - - - O + + + + Cl- Na+ hydrated ions H
Timberlake, Chemistry 7th Edition, page 287

8. Interstitial Spaces and Particle Size
(holes in water where substances dissolve)
100 mL
Parking at school if you arrive at 7:00 AM = _____
Easy
Parking at school if you arrive at 7:45 AM = _____
Hard
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

9. 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
volume
119 g
100 mL or
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
Add 3.0 mL water,stir…float
Add 3.0 mL water,stir…sink

10. Goals and Objectives: a
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
knowing before conducting your experiment 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 d.  Critique your own procedure, discuss and compare your process with
another group, then modify your own steps as needed e.  Repeat your experiment to check for accuracy, if time allows.

11. 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
the outcome of your results? 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)

12. Materials: electronic balance
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 :  ( 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!

13. of solubility on temperature
Solubility vs. Temperature for Solids
140 KI
KCl
NaNO3
KNO3
HCl
NH4Cl
NH3
KClO3
SO2
130
120
gases
solids
110
Solubility Table
100 90 80
shows the dependence
of solubility on temperature 70
Solubility (grams of solute/100 g H2O) 60 50
“Solubility Curves for Selected Solutes”
Description: This slide is a graph of solubility curves for 10 solutes. It shows the number of grams of solute that will dissolve in 100 grams of water over a temperature range of 0cC to 10 cC.
Basic Concepts
The maximum amount of solute that will dissolve at a given temperature in 100 grams of water is given by the solubility curve for that substance.
When the temperature of a saturated solution decreases, a precipitate forms.
Most solids become more soluble in water as temperature increases, whereas gases become less soluble as temperature increases.
Teaching Suggestions
Use this slide to teach students how to use solubility curves to determine the solubilities of various substances at different temperatures. Direct their attention to the dashed lines; these can be used to find the solubility of KClO3 at 50 cC (about 21 g per 100 g of H2O). Make sure students understand that a point on a solubility curve represents the maximum quantity of a particular solute that can be dissolved in a specified quantity of solvent or solution at a particular temperature. Point out that the solubility curve for a particular solute does not depend on whether other solutes also are present in the solution (unless there is a common-ion effect; this subject usually is covered at a later stage in a chemistry course).
Questions
Determine the solubilities (in water) of the following substance at the indicated temperatures: NH3 at 50 oC; KCl at 90 oC; and NaNO3 at 0 oC.
Which of the substances shown on the graph is most soluble in water at 20 oC? Which is lease soluble at that temperature? For which substance is the solubility lease affected by changes in temperature?
Why do you think solubilities are only shown between 0 oC and 100 oC?
In a flask, you heat a mixture of 120 grams of KClO3 and 300 grams of water until all of the KClO3 has just been dissolved. At what temperature does this occur? You then allow the flask to cool. When you examine it later, the temperature is 64 oC and you notice a white powder in the solution. What has happened? What is the mass of the white powder?
Compare the solubility curves for the gases HCl, NH3, and SO2) with the solubility curves for the solid solutes. What generalizations(s) can you make about the relationship between solubility and temperature?
According to an article in an engineering journal, there is a salt whose solubility in water increases as the water temperature increases from 0 oC to 65 oC. The salt’s solubility then decreases at temperatures above 65 oC, the article states. In your opinion, is such a salt likely to exist? Explain your answer. What could you do to verify the claims of the article? 40 30
NaCl 20 10
LeMay Jr, Beall, Robblee, Brower, Chemistry Connections to Our Changing World , 1996, page 517

14. 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).