FLOATS OR SINKS DENSITY

Density It is a measure of compactness of how much mass is tightly squeezed into a given volume. Is the ratio of mass and volume in an object. D= M/V g/ml or g/cm3

DENSITY D = m/v (g/cm3) (g/ml) Mass usually expressed in grams Volume usually expressed in cm3 or milliliters, etc.

Density Density = amount of matter per unit volume Density is the ratio of mass to volume If the volume stays the same and the mass increases . . . the density will increase If the mass stays the same and the volume increases . . . The density will decrease

The “DMV” Triangle for Volume, Mass, and Density ÷ ÷ D X V Volume = M D Mass = D x V

Density is the measure of the “compactness” of a material How close the atoms or molecules are to each other More than “heaviness” - density includes how much space an object takes up!! All substances have density including liquids, solids, and gases Bread slice and compacted bread in large flask of water

What would take up more space. A kilogram of feathers… What would take up more space??? A kilogram of feathers….. or a kilogram of steel?? ROCKS - pass around OR

“Compactness” Hot air balloon - Describe how a hot air balloon works. Defend your argument.

Density The density of water is 1.0 g/ml Objects with densities greater than 1.0 g/ml will sink in water

Objects with densities less than 1.0 g/ml will float on water Density Objects with densities less than 1.0 g/ml will float on water

Ice floats therefore it is less dense than water Ice mostly remains underwater with only a portion of it being exposed

Solids Ice vs. water…..

Gases How much kinetic energy do the molecules have?? The greater the kinetic energy ……the greater the volume …… and the less dense that gas is!! Therefore, cold air is more dense than warm air

Low pressure weather system means warmer air tends to rise, High pressure systems indicate a colder more dense air mass that will……. SINK!!!

LIQUIDS The more dissolved solids in a solution, the more dense (such as ocean water) Cold water in lakes tend to sink (this creates a constant mixing of water, nutrients, and other substances) Kinetic energy again!! Straw solute Denser layers to less dense layers…..

What would happen???? Mercury density = 13600kg/m3 Lead density = 11340kg/m3 Sinking vial - make it float

Lead floats on liquid mercury!

Solids Ice vs. water…..

SOLIDS Ice is less dense than water (which is why lakes and ponds have a thin layer of ice covering in winter, with water underneath) Various rocks, woods, metals have a characteristic density specific to that substance Beans/ping pong ball; Big jug of water in a pool Wouldn’t you like to have a bunch of THIS dense material?

Archimedes and the Kings Crown http://3quarksdaily.blogs.com/3quarksdaily/images/2007/07/18/archimedes.jpg 250 b.c., the Greek mathematician Archimedes - story

Calculations If 96.5 grams of gold has a volume of 5 cubic centimeters, what is the density of gold?

Calculation If 96.5 g of aluminum has a volume of 35 cm3, what is the density of aluminum?

Calculation If the density of a diamond is 3.5 g/cm3, what would be the mass of a diamond whose volume is 0.5 cm3?

What is specific gravity? A comparison of the density of a substance and the density of water is specific gravity

Density Table SINK or FLOAT In Water (D = 1.0 g/mL) Float Float Float (alcohol) Float (fuel)