Introduction%20to%20Density

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Introduction to Density

• Density is the measurement of the mass of an
  object per unit volume of that object.
• d m / V
• Density is usually measured in g/mL or g/cm3 for
  solids or liquids.
• Volume may be measured in the lab using a
  graduated cylinder or calculated using
• Volume length x width x height if a box or
• V pr2h if a cylinder.
• Remember 1 mL 1 cm3

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How to measure the density of a solid in the
laboratory.

• Obtain a clean graduated cylinder.
• Fill the graduated cylinder with enough water to
  cover the object. Record the volume
• Carefully place the object into the water filled
  graduated cylinder.
• Record the new water level.
• The volume of the object is the Vfinal Vinitial.

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Introduction to Density

• Example An object has a mass of 50.0 g and
  occupies a volume of 52.0 mL. What is its density?

d m / V 50.0 g / 52.0 mL 0.98 g/mL

• Example A cylinderical piece of metal is 2.03
  inches high and has a diameter 17.0 mm wide and
  weighs 31.599 g. Identify the metal.

Vpr2h p (1.70 cm/2)2 (2.03 in 2.54 cm/1in)
11.7 cm3 D m/V 31.599 g / 11.7 mL 2.70
g/mL The metal is aluminum!
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Practice Problems on density
15.9 mL

• ___________ 1. Calculate the volume, in
  microliters, of a cylinder that is 32.42 mm long
  with a diameter of 0.0789 cm.
•  ___________ 2. Calculate the density of a
  solution if 45.0 mL of the solution weighs 7.12 x
  10-2 kg.
•  ___________ 3. The Hope diamond weighs 45.52
  carats and has a density of 3.51 g/cm3. What is
  the volume of this diamond? (1 carat 200 mg)
•  ___________ 4. A plastic material weighing 2.2
  lb is shaped into a cylinder 13.5 cm in height
  and 6.8 cm in diameter. Will this object sink or
  float in water?
•  ___________ 5. A student fills a 50.0 mL
  graduated cylinder with 25.0 mL of water, then
  places a spherical object weighing 54.367 g into
  the graduated cylinder. The new volume is 41.5
  mL. Calculate the density of the object.

1.58 g/mL
2.59 cm3
2.0 g/cm3 sink
3.29 g/mL