# Volume and Density in the SI System why things float or sink…metrically Unit 1 – Lecture 4.

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Volume and Density in the SI System why things float or sink…metrically Unit 1 – Lecture 4

Metric Density and Water
Metric Density and Water The 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 water at 4 C having a volume of 1 cm3 [one cm3 = one mL]

Common SI Volume Conversions
Common SI Volume Conversions 1cm3 = 1mL 1,000cm3 = 1,000mL 1L = 1,000mL 1,000mL = 1L = 1,000cm3

Density Formula Knowing 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
Some Common Densities in g/cm3 Air 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 - 4C 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 g/cm3.

Will it float? When any two substances are mixed, the less dense substance will float on the more dene substance density differences cause convection

Convection Convection – circular currents or movements within a liquid or gas due to density differences of temperature for the same liquid: warmer = less dense rises cooler = more dense sinks

Practice Problem #1 A 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/mL going from g/mL  g/mL…no conversion needed d = m/v 18.9 g = __?__ 1.12 mL mL This sample has a density of g/mL; so no, it is not pure gold

Practice Problem #2 If the density of air = 1.30 g/L, how many grams of mass does a mL volume of air have? convert L  mL 250.0 mL = L d = m / v 1.30g = mass L L mass = .325 g

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