Unit 1 – Lecture 4

Metric Density and WaterThe SI system is better than the

English/Imperial system at converting length measurements to volume measurements.

Density of Water = 1 g / cm3 [same as 1 g / 1 mL]1 gram of waterat 4 Chaving a volume of 1 cm3 [one cm3 = one

mL]

Common SI Volume Conversions1cm3 = 1mL1,000cm3 = 1,000mL1L = 1,000mL1,000mL = 1L = 1,000cm3

Density FormulaKnowing the volume, mass, and/or density of a

substance will allow you to infer as to the missing quantity.

Density = mass d = m volume v

Mass = Density * Volume Volume = Mass / Density

Some Common Densities in g/cm3

Air 0.00129 Titanium 4.5

Wood – Cherry

0.433 Iron 7.86

Gasoline 0.721 Steel 8.03

Water – ICE 0.897 Brass 8.553

Mineral Oil 0.914 Copper 8.9

Paper 0.929 Silver 10.5

Water - 4C 1.000 Lead 11.37

Glass 2.6 Uranium 18.74

Aluminium 2.643 Gold 19.32

Sapphire 3.99 Platinum 21.3

Iridium, a rare metal found in asteroids, comets, and meteorites has the highest natural density at 22.16 g/cm3.

Will it float?When any two substances are mixed, the less

dense substance will float on the more dene substancedensity differences cause

convection

ConvectionConvection – circular currents or movements

within a liquid or gas due to density differences of temperaturefor the same liquid:

warmer = less dense rises

cooler = more densesinks

Practice Problem #1A gold-colored ring has a mass of 18.9 grams

and a volume of 1.12 mL. Is the ring pure gold? Pure gold is 19.3 g/mLgoing from g/mL g/mL…no conversion

neededd = m/v18.9 g = __?__ 1.12 mL 1 mLThis sample has a density of 16.875 g/mL;

so no, it is not pure gold

Practice Problem #2If the density of air = 1.30 g/L, how many

grams of mass does a 250.0 mL volume of air have?convert L mL

250.0 mL = .2500 Ld = m / v1.30g = mass L .2500Lmass = .325 g