Slide 1

Density How tightly the atoms are packed together in an object Slide 2 Density At the conclusion of our time together, you should be able to: 1.Define density 2.Calculate the density of a given object if given the volume and mass 3.Calculate the volume or mass if the density is given with the volume or mass Slide 3 Density Density = mass volume Mass = the amount of matter in an object Volume = the amount of space the object takes up Units = g/mL (liquid) OR g/cm 3 (solid) Slide 4 DENSITY - an important and useful (qualitative) intensive physical property Mercury 13.6 g/cm 3 21.5 g/cm 3 Aluminum 2.7 g/cm 3 Platinum Slide 5 Familiar Saying A rotating lithoidal fragment never accrues lichen. A rolling stone gathers no moss!! Slide 6 Density Calculations M DV Cover up whatever unit you are solving for, the two units remaining will show you how to solve the problem. Slide 7 Density Calculations Regularly Shaped Solid : mass = balance volume = measure (l x w x h) Irregularly Shaped Solid: mass = balance volume = water displacement Slide 8 Density Calculations Liquid: volume = read graduated cylinder mass = tare graduated cylinder, mass liquid Slide 9 Problem A piece of copper has a mass of 57.54 g. It is 9.36 cm long, 7.23 cm wide, and 0.95 mm thick. Calculate density (g/cm 3 ). M DV Slide 10 Strategy 1. Get dimensions in common units. 2. Calculate volume in cubic centimeters. 3. Calculate the density. Slide 11 SOLUTION 1. Get dimensions in common units. 2. Calculate volume in cubic centimeters. 3. Calculate the density. (9.36 cm)(7.23 cm)(0.095 cm) = 6.4 cm 3 Note only 2 significant figures in the answer! Slide 12 Euphemisms in Science We all know that some politicians and government spokesmen use certain euphemistic phrases to give an aura of respectability to descriptions of events or actions which would be offensive when expressed in plain English. The following is a list of Euphemisms in Science and their translations into plain English. These results are correct within an order of magnitude... Wrong! Slide 13 DENSITYDENSITY Density is a (qualitative) intensive property of matter. does NOT depend on quantity of matter. like temperature Contrast with (quantitative) extensive property depends on quantity of matter. like mass and volume. StyrofoamBrick Slide 14 PROBLEM: Mercury (Hg) has a density of 13.6 g/cm 3. What is the mass of 95 mL of Hg in grams? In pounds? Slide 15 1.Use density to calculate mass (g) from volume. 2.Convert mass (g) to mass (lb) Need to know conversion factor = 454 g / 1 lb First, note that 1 cm 3 = 1 mL Strategy Slide 16 1.Convert volume to mass 2. Convert mass (g) to mass (lb) Strategy Slide 17 Learning Check Osmium is a very dense metal. What is its density in g/cm 3 if 50.00 g of the metal occupies a volume of 2.22 cm 3 ? 1) 2.25 g/cm 3 2)22.5 g/cm 3 3)111 g/cm 3 Slide 18 Solution 2) Placing the mass and volume of the osmium metal into the density setup, we obtain D = mass = 50.00 g = volume2.22 cm 3 volume2.22 cm 3 = 22.522522 g/cm 3 = 22.5 g/cm 3 = 22.522522 g/cm 3 = 22.5 g/cm 3 Slide 19 Learning Check Osmium is a very dense metal. What is its density in g/cm 3 if 50.00 g of the metal occupies a volume of 2.22 cm 3 ? 1) 2.25 g/cm 3 2)22.5 g/cm 3 3)111 g/cm 3 Slide 20 Volume Displacement A solid displaces a matching volume of water when the solid is placed in water. 33 mL 25 mL Slide 21 Learning Check What is the density (g/cm 3 ) of 48 g of a metal if the metal raises the level of water in a graduated cylinder from 25 mL to 33 mL? 1) 0.2 g/ cm 3 2) 6 g/m 3 3) 252 g/cm 3 33 mL 25 mL Slide 22 A.P. TEST IN AMERICAN HISTORY There is a red telephone on your desk. Start World War III. Report in length on its socio-political effects on the United States, if any. Slide 23 Density Lets see if you can: 1.Define density 2.Calculate the density of a given object if given the volume and mass 3.Calculate the volume or mass if the density is given with the volume or mass Slide 24 Learning Check Which diagram represents the liquid layers in the cylinder? (K) Karo syrup (1.4 g/mL), (V) vegetable oil (0.91 g/mL,) (W) water (1.0 g/mL) 1) 2) 3) K K W W W V V V K Slide 25 Learning Check The density of octane, a component of gasoline, is 0.702 g/mL. What is the mass, in kg, of 875 mL of octane? 1) 0.614 kg 2) 614 kg 3) 1.25 kg Slide 26 Learning Check If blood has a density of 1.05 g/mL, how many liters of blood are donated if 575 g of blood are given? 1) 0.548 L 2) 1.25 L 3) 1.83 L 4) 548 L 4) 548 L Slide 27 Learning Check A group of students collected 125 empty aluminum cans to take to the recycling center. If 21 cans make 1.0 pound of aluminum, how many liters of aluminum (D = 2.70 g/cm 3 ) are obtained from the cans? 1) 1.00 L2) 2.00 L 3) 4.00 L Slide 28 Which is heavier, a quart of water or a quart of mercury? If we have equal volumes of two different substances, then the one with the greater density will have the greater mass. Water has a density of 1.0 g/ml and mercury (Hg) has a density of 13.6 g/ml. Slide 29 15 Helpful Hints On The Lab Report from Mr. Ts Vast Lab Experience!!! Hint #11. Given the most inappropriate time for something to go wrong, that's when it will occur. Slide 30 Which is heavier, a ton of feathers or a ton of bricks? Which is larger? If two objects have the same mass, the one with the higher density will be smaller. Neither Feathers