To determine the density of a substance, you need to measure both its mass and its volume. From the mass and volume, the density is calculated. If the mass is measured in grams and the volume is measured in mL, the density will have a unit of g/mL.
PROCEDURE
Density of a material
 mass of material volume of material
 grams of material mL of material
A.
Density of a liquid a.
Place about 20 mL of water in a graduated cylinder. Determine the volume exactly from the markings on the cylinder. Record the volume in mL to one decimal place.
Volume of water: ___________mL b.
The mass of the liquid is determined by weighing by difference. Alternatively, you may use the
“zeroing” feature of the balance instead. First, determine the mass of a 50-mL dry beaker. Pour the water from the cylinder into the beaker, and reweigh. Record the mass, writing down all the digits in the display. Calculate the mass of the water. Finally, determine the density of water.
Mass of water:____________g
Density of water (use formula above): __________________
Show calculations!
Instructor’s Initial_______ c.
Repeat the same procedure for another liquid assigned by your instructor.
Put your data here. Label the information, and use the appropriate units.
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B.
Density of a solid a.
Obtain a solid metal cylinder and record the letter on it. Determine the mass and record.
Letter on metal cylinder:________ Mass of cylinder:___________ b.
Take out your 50 mL graduated cylinder, and fill it with water until the cylinder is about half full.
Then, read the exact volume of water and record it.
Volume of water in cylinder: ____________mL ( How many decimal places?) c.
Slowly lower the metal object into the water. Measure and record the final volume when the object is completely submerged.
Volume of water + metal cylinder: ____________mL d.
Calculate the volume of the metal. Then, determine the density of the solid.
Show your calculations and data here.
Density of the solid metal cylinder: __________________ (Units?)
C.
The Separation of a Salt-Water mixture a.
Determine the mass of a piece of weighing paper on the balance. Then, weigh out about 1.5 grams of salt (NaCl) onto the paper. Determine the exact mass of salt that you used. Be sure to clean the balance pan when you are done!
Mass of salt (to three decimal places): _______________ ( you supply the units from now on) b.
Pour the salt into a 150 mL beaker. Then, pour about 5 mL of DI water into the beaker and stir to dissolve all of the salt. If the salt does not dissolve after a few minutes of stirring, add more water, bit by bit, and stir until the salt does dissolve. You want to use as little water as possible, c.
Determine the mass of your empty evaporating dish. Then, pour your salt water mixture into it.
Mass of evaporating dish: ___________________ (Did you write down all digits from the balance?)
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d.
Set-up a steam bath like that in figure 3-1. Set the evaporating dish on top of the steam bath, making sure that the evaporating dish is completely supported by the beaker. Allow all the water in the solution to evaporate.
Some tips: First, choose the size of beaker which the evaporating dish will fit best into, just like you see in the diagram. The dish should not fall in to the beaker, nor should it be too large to rest on its rim. The beaker should be filled about halfway to the top with tap water (why not DI water?).
This should be enough. Do not add cold water to the beaker once it is hot or it may shatter! iron ring ring stand evaporating dish beaker holding water wire gauze
Bunsen burner
Figure 3-1: Steam Bath Assembly e.
Remove the evaporating dish from the beaker carefully using your crucible tongs. Using the beaker tongs provided by the instructor, remove the beaker holding the boiling water. Dry the evaporating dish completely by placing it on the wire gauze and heating it directly with the flame for about 2 minutes. f.
Turn off the flame and allow the dish to cool for about 10 minutes. g.
Determine the mass of the evaporating dish with the salt residue in it. Calculate the percent of the salt that you were able to recover.
Mass of Evaporating Dish + Salt Residue: ______________ Calculations
Mass of Salt Resdidue: _________________
Percent of Salt Recovered: ______________% % recovery
 mass of salt residue

100 % mass of salt used
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h.
Wash the salt residue down the drain.
D.
Determining the Percent of Salt in an Unknown Solution a.
Rinse the evaporating dish you used in the last section with DI water, and then dry it with a paper towel. Try your best to remove all visible water. b.
Select an unknown sample (A, B, or C) from the cart. Your instructor may assign you one.
Immediately write down the letter of the unknown you are using on the report sheet.
Unknown:__________ c.
Pour about 5-7 mL of one of the three unknown salt solutions into the evaporating dish.
Carefully place this on the balance and record the mass.
Mass of evaporating dish + salt solution: __________________
Mass of salt solution: _____________________ (You already determined the mass of the dish) d.
Set the evaporating dish on top of the steam bath you assembled in the previous section. Allow all the water in the solution to evaporate. e.
Dry the evaporating dish completely by placing it on a wire gauze and heating it directly with the flame for about 2 minutes. Turn off the flame and allow the dish to cool for about 10 minutes. f.
Determine the mass of the evaporating dish with the salt residue in it. Calculate the percent of the salt in the unknown solution.
Mass of evaporating dish + salt residue: _________________
Mass of salt residue: _____________________ (Again, you should know the mass of the dish) g.
Wash the salt residue down the drain.
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Report Sheet Name ____________________
Always give the appropriate units!
A.
Density of a liquid
Liquid 1 Liquid 2
Name of the liquid
Volume of the liquid
Mass of beaker
Mass of beaker + liquid
Mass of the liquid
Density of the liquid
Show calculations for density:
B.
Density of a Solid
Mass of the solid ____________________________
Volume of the solid by displacement:
Initial water level ____________________________
Final water level with solid ____________________
Volume of the solid __________________________
Density of the solid __________________________
Show calculations:
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C. Separation of a Mixture
Mass of weighing paper
Mass of weighing paper and salt
Mass of salt (show calculation)
Mass of evaporating dish
Mass of evaporating dish and salt residue
Mass of salt residue (show calculation)
_______________ g
_______________ g
_______________ g
_______________ g
_______________ g
_______________ g
% recovery
 mass of salt residue mass of salt used
Percent of salt recovered (show calculation)

100 %
_______________ %
Was your salt-water mixture a homogenous mixture or a heterogeneous one?
Judging by your percent recovery, how successful were you at separating all of the salt from the water? If your value was either greater or lower than 100%, explain how this could have occurred.
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D. Percent of Salt in an Unknown Solution
Unknown
Mass of evaporating dish (from Part C)
Mass of evaporating dish and solution
Mass of solution (show calculation)
Mass of evaporating dish and salt residue
obtained after heating
Mass of salt residue (show calculation)
___________
_______________ g
_______________ g
_______________ g
_______________ g
_______________ g
% salt
 mass of salt residue

100 % mass of solution
Percent salt in solution (show calculation) _______________ %
Questions
Suppose you have 10. mL of water in one beaker #1 and 25. mL of the same water in beaker #2. Is the density of the water in beaker #2 greater than the density of the water in beaker #1? Explain.
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Suppose that you have 25. mL of distilled water and 25. mL of sea water. Should one sample have a greater mass than the other, and, if so, which one? Explain
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Materials for this lab:
Liquids for density tests: Toluene, Methylene Chloride, Ethanol (95%), Methanol (two 250 mL bottles of each, labeled with name)
Coke, diet coke, pepsi, diet pepsi : one can each
Unknown metal cylinders A, B, C, D
Sodium chloride (3 small containers, about 10+ grams each)
Unknown salt solutions: Prepare 500 g of each according to directions below. Label as “Unknown
A”, “Unknown B”, and “Unknown C”
Unknown A: 10 g NaCl + 490 mL water
Unknown B: 20 g NaCl + 480 mL water
Unknown C: 15 g NaCl + 485 mL water
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