Density NOTES

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Density NOTES

  1. 1. DENSITY
  2. 2. Warm-up:Why is it easier for your body to float in theocean rather than in your swimmingpool?
  3. 3. DENSITY:• Intensive property – it does not depend onthe amount of matter.• Units are g/mL or g/cm3• Density is constant for all sample sizes of agiven substance.
  4. 4. Osmium is a very dense metal. What is itsdensity in g/cm3 if 50.00 g of the metal occupiesa volume of 2.22cm3?1) 2.25 g/cm32) 22.5 g/cm33) 111 g/cm3Practice Problem #1
  5. 5. 2) Placing the mass and volume of the osmium metalinto the density setup, we obtainD = mass = 50.00 g =volume 2.22 cm3= 22.522522 g/cm3 = 22.5 g/cm3SOLUTION
  6. 6. Practice Problem #2:1. Calculate the density of a piece of leadmetal that has a mass of 125.2 g and avolume of 11.0 mL.
  7. 7. Problem A piece of copper has a mass of57.54 g. It is 9.36 cm long, 7.23 cm wide, and0.95 mm thick. Calculate density (g/cm3).Density mass (g)volume (cm3)
  8. 8. Strategy1. Get dimensions in common units.2. Calculate volume in cubiccentimeters.3. Calculate the density.
  9. 9. SOLUTION1. Get dimensions in common units.2. Calculate volume in cubic centimeters.3. Calculate the density.0.95 mm •1cm10 mm= 0.095 cm57.54 g6.4 cm3= 9.0 g/ cm3(9.36 cm)(7.23 cm)(0.095 cm) = 6.4 cm3Note only 2 significant figures in the answer!
  10. 10. Percent ErrorMeasures how accurate the experimental data is.(experimental value) − (true value)% error = × 100true value
  11. 11. Example:• A metal block has a true value of 1.70 g/cm3.A student measures the density of the block tobe 1.85 g/cm3. Calculate the percent error forthis measurement.
  12. 12. Example• A student measured the density of water threetimes and obtained the following results:Trial 1: 0.996 g/mLTrial 2: 1.03 g/mLTrial 3: 0.964 g/mLWater has a density of 1.00 g/mL.A. Calculate the student’s percent error for eachtrial.B. Which trial had the greatest percent error?
  13. 13. PROBLEM: Mercury (Hg) has a density of13.6 g/cm3. What is the mass of 95 mL ofHg in grams? In pounds?
  14. 14. PROBLEM: Mercury (Hg) has a density of 13.6 g/cm3.What is the mass of 95 mL of Hg?Strategy1. Use density to calc. mass (g) from volume.2. Convert mass (g) to mass (lb)Need to know conversion factor= 454 g / 1 lbFirst, note that 1 cm3 = 1 mL
  15. 15. PROBLEM: Mercury (Hg) has a density of 13.6 g/cm3.What is the mass of 95 mL of Hg?1. Convert volume to mass95 cm3 •13.6 gcm3= 1.3 x 103 g1.3 x 103 g •1 lb454 g= 2.8 lb2. Convert mass (g) to mass (lb)
  16. 16. A solid displaces a matching volume of waterwhen the solid is placed in water.33 mL25 mLVolume Displacement
  17. 17. What is the density (g/cm3) of 48 g of a metal ifthe metal raises the level of water in a graduatedcylinder from 25 mL to 33 mL?1) 0.2 g/ cm3 2) 6 g/m3 3) 252 g/cm333 mL25 mLLearning Check
  18. 18. Which diagram represents the liquid layersin 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)KWWVVKWVKLearning Check
  19. 19. If blood has a density of 1.05 g/mL, how manyliters of blood are donated if 575 g of blood aregiven?1) 0.548 L2) 1.25 L3) 1.83 LLearning Check
  20. 20. The density of octane, a componentof gasoline, is 0.702 g/mL. What isthe mass, in kg, of 875 mL of octane?1) 0.614 kg2) 614 kg3) 1.25 kgLearning Check
  21. 21. If blood has a density of 1.05 g/mL, how manyliters of blood are donated if 575 g of blood aregiven?1) 0.548 L2) 1.25 L3) 1.83 LLearning Check
  22. 22. A group of students collected 125 emptyaluminum cans to take to the recycling center. If21 cans make 1.0 pound of aluminum, howmany liters of aluminum (D=2.70 g/cm3) areobtained from the cans?1) 1.0 L 2) 2.0 L 3) 4.0 LLearning Check

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