• Measure of the amount of matter present in an object
– weight measures the gravitational pull on an object, which depends on its mass
– Weight and mass are NOT the same thing
• SI unit = gram (g)
– about 2 lbs. 3 oz.
• Commonly measure mass in grams (g) or milligrams (mg)
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Molecular Approach
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• The amount of space an object takes up.
• Could be expressed in units of liters (liquid)
• Could be expressed in units of length cubed, m 3
(solid)

• Derived unit
– any length unit cubed
• Measure of the amount of space occupied
• SI unit = cubic meter (m 3 )
• Commonly measure solid volume in cubic centimeters (cm 3 )
• Commonly measure liquid or gas volume in milliliters (mL)
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Molecular Approach
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What is the volume of the fish?

• two main physical properties of matter
• even though mass and volume are individual properties, for a given type of matter they are related to each other!
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Molecular Approach
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• Density is the ratio of mass to volume

• The density of solids is the greatest, followed by liquids, and lastly gases
– except ice is less dense than liquid water!
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Molecular Approach
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