DENSITY Is a physical property of Elements Depends on: Mass Volume D = m/v (g/cm3) Mass usually expressed in grams Volume usually expressed in cm3 or liters, etc.

Density is the measure of the “compactness” of a material More than just the “heaviness” of a substance, 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

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

Gases How much kinetic (moving) 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

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

Balloon and liquid nitrogen http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/balloon.html#c1 http://paer.rutgers.edu/pt3/movies/TVrhoandFb.mov What happens to the gasses in the balloon when it is placed in liquid nitrogen? (nitrogen condensed to -196 degrees celcius) www.dkimages.com

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! http://www.zyra.tv/merc16a.htm

Solids Ice vs. water….. http://hyperphysics.phy-astr.gsu.edu/hbase/chemical/waterdens.html

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? Microsoft Clip Art 2007

Archimedes and the Kings Crown 250 b.c., the Greek mathematician Archimedes - story Microsoft Clip Art 2007 http://www.chemistryland.com/CHM130S/02-MMM/Measure/Measuring.htm

Factors affecting Density Temperature Pressure Microsoft Clip Art 2007 Add several drops of red food color to each of two 250-mL Erlenmeyer flasks; fill them with warm tap water. (If tap water is not warm, heat some tap water on a hot plate to 40-45 °C.) Add several drops of blue food coloring to each of the other two 250-mL Erlenmeyer flasks; fill them with cool tap water. Predict the outcome when one flask is inverted over the other. Place a paper card on top of the vessel filled with warm water. Invert the flask making sure to hold the card in place. Stack it on top of one of the cool water flasks. Remove the card. Remain prepared to catch the flasks.   ** Visual here. Place a paper card on top of the flask filled with cool water. Invert the flask making sure to hold the card in place. Stack it on top of the other warm water flask. Remove the card. Wide mouth containers may also be used. Microsoft Clip Art 2007

Factors affecting Density Dissolved solids – in liquids Concentration and kind of substances

FACTORS AFFECTING DENSITY ATomS!!!!

Relative Density The density of a material or substance, relative to another substance Expressed in a ratio: water = 1g/cc Water is the substance to which we generally compare other substances ALSO known as SPECIFIC GRAVITY Relative Liquid densities: Oil, colored water, and corn syrup in a graduated cylinder. An H2O ice cube floats in liquid H2O but floats in rubbing alcohol. A can of diet coke floats in water while a can of regular coke sinks (can determine density of sugar versus NutraSweet using balance).

How are Submarines like fish…. Microsoft Clip Art 2007 Microsoft Clip Art 2007 How are Submarines like fish…. The swim bladder in bony fish control their relative density in order to rise or dive in the water….buoyancy When air is added to the swim bladder, by diffusion through the blood vessels in the bladder walls, the fish becomes less dense overall when air is removed fish become more dense By changing the volume of air in the bladder, the fish’s density can be made equal to that of the surrounding water at a given depth. Air bladder when pulled up to quickly

DETERMINING DENSITY Regular Shapes – mass, then determine the volume by formula EX: cubes, cylinders, spheres, cones, etc. Irregular shapes – mass, then measure displacement of a liquid (usually water) by that irregularly shaped object http://www.chemistryland.com/CHM130FieldLab/Lab1/Lab1.html http://www.chemistryland.com/CHM130FieldLab/Lab1/Lab1.html

Density Triangle The density triangle provides you to check your answer and to make sure you calculating correctly. X dyscalculiaforum.com 

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 Microsoft Office Word Clipart 2007 http://www.neonhusky.com/JShop/shopimages/products/normal/CJ-M73.jpg