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DENSITY. How dense is dense?. What’s the matter?. Matter exists in 3 main forms: solid liquid and gas. Density is the concentration of matter (atoms) in a substance. Silicon atoms. Density is a ratio. The density of an object is the ratio of its mass (g) to its volume (cm 3 or ml). A. B.
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DENSITY How dense is dense?
What’s the matter? • Matter exists in 3 main forms: solid liquid and gas. • Density is the concentration of matter (atoms) in a substance. Silicon atoms
Density is a ratio • The density of an object is the ratio of its mass (g) to its volume (cm3 or ml). A B C
Density calculations convert to metric 2.54cm = 1 inch Length = ? Width = ? Height = ? Volume = ? 454g = 1lb Mass = 30.98lb Mass = ? 7 X 3.625 X 1.75in.
Density equation • Density = Mass Volume • D = M V M V D
Density calculations 2.54cm = 1 inch Length = 17.78cm Width = 9.21cm Height = 4.45cm Volume = ? 454g = 1lb Mass = 30.98lb Mass = 14,064.9g 7 X 3.625 X 1.75in.
Work Volume 17.78cm X 9.21cm X 4.45cm = 728.7 cm3 Volume = 728.7 cm3 Mass 30.98lb X 454g = 14,064.9g 1lb Mass = 14,064.9g
More work D = M V D = 14,064.9g 728.7 cm3 D = ?
More work D = M V D = 14,063.9 g 728.7 cm3 D = 19.3 g/cm3
Effect of phase of matter on density • Most substances increase in density as they change from gas to liquid to solid. • Quite simply, the atoms are closest together in the solid phase. gas E liquid E solid decreasing density increasing density
Water is an exception ice liquid water water vapor • Water is densest as a liquid at 3.98oC. That’s why ice floats.
Size or shape does not affect the density of a substance = same density = same density
Factors that affect density • Temperature • Heat - pushes molecules apart • Cold - pushes molecules together • Pressure • Low - allows molecules to spread apart • High - pushes molecules together • It’s the volume that changes and density is dependent on the ratio d=m v
Float? • If the density of an object is less than the liquid it will float. • The lower the density of an object the higher it will float in the liquid.
Sink? • If the density of an object is greater than that of the liquid, it will sink.
??? • If an object and a liquid have the same density, the object can remain stationary anywhere in the liquid.
Layering • Liquids of different densities will form layers. http://www.youtube.com/watch?v=-CDkJuo_LYs