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Density >
Slide 1 of 25
Determining Density
Density
3.4
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Slide 2 of 25
Density > Determining Density
Density: mass of an object per unit volume.
3.4
~ Intensive property that depends only on the composition of a substance, not on the size of the sample.
Table T
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Slide 3 of 25
Density > Determining Density
The density of corn oil is less than the density of corn syrup. For that reason, the oil floats on top of the syrup.
Density of water at room temp = 1.0 g/mL
Density of ice = .92g/mL
3.4
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Slide 4 of 25
Density > Determining Density
Mass: measured on a balance, grams
Volume: solid – regular shape – l x w x h, cm3
irregular shape – water displacement
if m = 4 g, what is the density?
d = 4 g/ 2 mL = 2 g/mL
will it sink or float in water?
Volume: liquid – use graduated
cylinder
3.4
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SAMPLE PROBLEM
Slide 5 of 25
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3.11
Now, use dimensional analysis to solve for the volume!
3
3
10.5 14
1.3
md
Vg g
cm V
V cm
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SAMPLE PROBLEM
Slide 6 of 25
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tin = Sn
Aug ’10
3
3
95.047.31 /
13.0
md
Vg
g cmV
V cm
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SAMPLE PROBLEM
Slide 7 of 25
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June ’10 ans: (2) 2
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SAMPLE PROBLEM
Slide 8 of 25
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SPECIFIC GRAVITY
~is the relationship of density to a standard
S.G. = density of a substance density of standard~has no unit
~density of standard for solids & liquids is water, =1g/mL
~density of standard for gases is air, d=1.29g/L
be careful!!!! memorize
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SAMPLE PROBLEM
Slide 9 of 25
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Oxygen gas has a density of 0.001429 g/cm3. Determine its specific gravity.
Density of a gas must be in g/L to compare with air for SG.
Answer:
1.429 /
1.29 /
g LSG
g L
= 1.1107751938Final ans. (with SF): 1.108
3
3
0.001429 1 10001.429 /
1 1
g cm mLg L
cm mL L
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SAMPLE PROBLEM
Slide 10 of 25
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Determine the mass of a bar that measures 12. cm x 20. cm x 1.0 cm. It has a specific gravity of 2.78.
Density of a solid must be in g/cm3 to compare with water for SG.
Answer: 3
2.781 /
densityofbar
g cm
3
3 3
2.78 /12. 20. 1.0
2.78 / 240 667.2
massdensityofbar g cm
cm x cm x cm
m g cm x cm g
Final ans. with SF: 670 g
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SAMPLE PROBLEM
Slide 11 of 25
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3.10
EXTRA EASY PROBLEM