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Density and % error

Density and % error. M V. M. D =. D. V. Density. Density – Compares mass (amount of matter) of object to its volume (amount of space occupied) mass per unit volume (g/cm 3 ). Density. Mass is always in g Volume is always in cm 3 If not… you must convert Note: I L = 1dm 3

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Density and % error

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  1. Density and % error

  2. M V M D = D V Density • Density – Compares mass (amount of matter) of object to its volume (amount of space occupied) • mass per unit volume (g/cm3)

  3. Density • Mass is always in g • Volume is always in cm3 • If not… you must convert • Note: • I L = 1dm3 • 1mL = 1 cm3 g/ cm 3 Is considered to be a derived unit because it combines 2 SI units

  4. Example • Calculate the density of an object that has a volume of 4.67 cm3,and a mass of 56.9 g • D = m V • D= x • M= 56.9g • V= 4.67 cm3

  5. Examples • X = 56.9g 4.67 cm3 • x=12.2 g/cm3 • * RULE FOR SIGNIFICANT DIGITS WHEN MULTIPLYINMG OR DIVIDING APPLY HERE

  6. M D V Density • An object has a volume of 825 cm3 and a density of 13.6 g/cm3. Find its mass. GIVEN: V = 825 cm3 D = 13.6 g/cm3 M = ? WORK: M = DV

  7. WORK: V = M D M D V Density A liquid has a density of 0.87 g/mL. What volume is occupied by 25 g of the liquid? GIVEN: D = 0.87 g/mL V = ? M = 25 g

  8. WORK: D = M V M D V Density You have a sample with a mass of 620 g & a volume of 753 cm3. Find density. GIVEN: M = 620 g V = 753 cm3 D = ?

  9. Ways to determine density 1. Regularly shaped objects – direct volume measurement (l x w x h) 2. Irregularly shaped objects- use water displacement method (graduated cylinder) to find volume. Note: mass is found the same way regardless the shape of the object

  10. Density • I have a block that measures 5.25 cm by 2.25 cm by 8.50 cm. • I weigh the block and find its mass to be 5.85 g • Calculate the density of the block in g/cm3

  11. For example • A chunk of metal has a mass of 5.25 g. It is placed in a graduated cylinder containing 25.0 ml of water. Once the metal is placed in the graduated cylinder, the water rises to 38.2 ml. What is the density of the metal?

  12. % error • % error – the deviation from the accepted value during an experiment. Usually caused by human error. • % error = (your value - literature value)x 100 • literature value • It is always a positive number Page 38 in textbook has a list of densities

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