Density Notes- Part 1
Chemistry 1
1
Density
• The compactness and size of the molecules or particles
of a substance
– the more compact or squished together the molecules are and
the more mass the particles have, the larger the density
• The relationship between an object’s MASS and
VOLUME
• Density is a characteristic property of substances and
can be used to help identify substances.
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• MASS is the amount of matter an object
contains
– Mass does not change unless you add or
remove matter
• VOLUME is the amount of space an object
occupies
• Density = Mass
Volume
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Finding Mass and Volume
• Mass is always determined using a
balance.
– Triple beam or electronic
• Remember you always must take into
account the mass of the container one of
two ways:
– Tare the balance (zero out the container’s
mass)
– Or measuring the mass of the container and
then subtracting it out later from the total
mass of the container + substance
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• Volume can be found in different ways,
depending on the substance or object.
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• Liquid volumes are
read in volumetric lab
equipment, like a
graduated cylinder or
pipet.
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• The dimensions of
regularly shaped objects
may be measured and
then the volume found by
using a formula such as
V=l x w x h.
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• The volume of irregularly
shaped objects may be
found by water
displacement
•
measure a given amount
of water in a graduated
cylinder
• add the object and read
the volume of the water +
object
• then find the volume of the
object by subtraction.
Amount of H2O with object =
______
About of H2O without object =
______
Difference = Volume = ______
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Units
• Mass units are usually grams (g)
• Volume units are usually
– Milliliters (mL) or cubic centimeters (cm3) for
liquids or solids
• 1mL = 1cm3
– L for gases
• Density units will always be a
Mass unit
volume unit
like g/mL or g/cm3 or g/L
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Using the density formula
• D=m/v can be used to solve for density if
the mass and volume is known
• What if the density is known, and you
need to find the mass or volume?
– Just rearrange the formula to solve for the
unknown
m=Dv or v=m/D
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examples
A 10.0mL sample of a sugar solution has a
mass of 5.0g. What is the density of the
sugar solution?
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• A piece of metal has a mass of 114g and a
volume of 10.0cm3. What is the density of
the metal?
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• A substance’s density is known to be
5.6g/mL. You have a 25.0mL sample of
the substance. What is the mass of the
sample?
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