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# Density

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1. Density How tightly the atoms are packed together in an object

2. DensityAt the conclusion of our time together, you should be able to: Define density Calculate the density of a given object if given the volume and mass Calculate the volume or mass if the density is given with the volume or mass

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/cm3 (solid)

4. Platinum Mercury Aluminum DENSITY - an important and useful (qualitative) intensive physical property 13.6 g/cm3 21.5 g/cm3 2.7 g/cm3

5. Familiar Saying A rotating lithoidal fragment never accrues lichen. A rolling stone gathers no moss!!

6. Density Calculations M D V Cover up whatever unit you are solving for, the two units remaining will show you how to solve the problem.

7. Density Calculations • Regularly Shaped Solid : mass = balance volume = measure (l x w x h) • Irregularly Shaped Solid: mass = balance volume = water displacement

8. Density Calculations • Liquid: volume = read graduated cylinder mass = tare graduated cylinder, mass liquid

9. ProblemA 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/cm3). M D V

10. Strategy 1. Get dimensions in common units. 2. Calculate volume in cubic centimeters. 3. Calculate the density.

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 cm3 Note only 2 significant figures in the answer!

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!

13. PROBLEM: Mercury (Hg) has a density of 13.6 g/cm3. What is the mass of 95 mL of Hg in grams? In pounds?

14. Strategy First, note that1 cm3 = 1 mL 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

15. Strategy 1. Convert volume to mass 2. Convert mass (g) to mass (lb)

16. Learning Check Osmium is a very dense metal. What is its density in g/cm3 if 50.00 g of the metal occupies a volume of 2.22 cm3? 1) 2.25 g/cm3 2) 22.5 g/cm3 3) 111 g/cm3

17. Solution 2) Placing the mass and volume of the osmium metal into the density setup, we obtain D = mass = 50.00 g = volume 2.22 cm3 = 22.522522 g/cm3 = 22.5 g/cm3

18. Learning Check Osmium is a very dense metal. What is its density in g/cm3 if 50.00 g of the metal occupies a volume of 2.22 cm3? 1) 2.25 g/cm3 2) 22.5 g/cm3 3) 111 g/cm3

19. Volume Displacement A solid displaces a matching volume of water when the solid is placed in water. 33 mL 25 mL

20. Learning Check What is the density (g/cm3) 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/ cm3 2) 6 g/m3 3) 252 g/cm3 33 mL 25 mL

21. 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.

22. DensityLet’s see if you can: Define density Calculate the density of a given object if given the volume and mass Calculate the volume or mass if the density is given with the volume or mass

23. 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 W V V K W W V K

24. 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

25. 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

26. 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/cm3) are obtained from the cans? 1) 1.00 L 2) 2.00 L 3) 4.00 L

27. Water has a density of 1.0 g/ml and mercury (Hg) has a density of 13.6 g/ml. 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.

28. 15 Helpful Hints On The Lab Report from Mr. T’s Vast Lab Experience!!! Hint #11. Given the most inappropriate time for something to go wrong, that's when it will occur.

29. Which is heavier, a ton of feathers or a ton of bricks? Neither • Which is larger? Feathers • If two objects have the same mass, the one with the higher density will be smaller.