DENSITY

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DENSITY

• Density MASS
• Volume

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MASS

• How heavy an object is.
• Quantity of matter observed in an object.
• Measured in kg, g, or mg
• WE FEEL MASS (Atoms).

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VOLUME

• The size of an object.
• The amount of space occupied by an object.
• Measured in L, ml, cm3.
• -WE SEE VOLUME!! (3-D).

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EXAMPLE

• An object has a mass of 20 grams and a volume
  of 10 milliliters.
• What is the density of this object?

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• Density 20 grams
• 10 mL
• Density 2 g/mL

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• The density of a substance is always the same,
  no matter how large or small the sample is

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• Water---1 g/mL, 1 g/cm3
• Iron---7.9 g/cm3
• Lead---11.3 g/cm3
• Gold---19.3 g/cm3

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• Why do some objects float in water?
• Why does a hot air balloon rise?
• Why are the oceans (Hydrosphere) always below the
  air (Atmosphere)?
• The solid earth, crust (lithosphere) is the most
  dense part of earth.

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To change Mass of an object

• Cut the object in ½, you will have two pieces
  each with ½ the mass and ½ the volume of the
  original.
• This does not change density (½ the mass ½ the
  volumeCheck the density formula)!
• Add more atoms to the object, you will also be
  increasing the volume.
• Same MASS per VOLUME as before (check it out)!
  Density stays the same!

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Ways to change volume of an object

• Change the temperature of an object. Compress the
  object (ex, Aluminum cube).
• This does change density (same mass, more or less
  volume).
• Cut an object into different pieces.
• Does not change density (Cut object in ½ you have
  two pieces each with ½ the mass and ½ the volume
  of the original.

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• The only way to CHANGE DENSITY is to cause a
  change in VOLUME without changing MASS.
• This can only happen through a TEMPERATURE CHANGE
  and/or a PHASE CHANGE.

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PERCENT ERROR

• Compares a measurement with the accepted value.
• Copy formula here from reference tables
• Subtract
• Divide
• Then multiply