Density and Percent Error

Percent Error

○ There are two types of error in measurement:

○ Systematic error → error is in one direction only

○ Ex. Bathroom scale always reads 2 pounds

○ Random error → error that fluctuates in both

directions

○ Ex. Bathroom scale says 2 pounds one time, and 100

pounds the next time

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Percent Error

○ The melting point of carbon is 3,550 degrees Celsius. In

lab, a student calculated the melting point as 3,446
degrees Celsius. What is the student’s percent error?

3446 – 3,550
___________ X 100 = 2.93%
3,550

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Density-Amount of matter present in a given
volume of substance (how compact is it?

○
○

D = m

v

○ Units are g (for solids) or g (for liquids)

cm3

mL

○ Ex. A block has a volume of 25.3 cm3. Its mass is

21.7 g. What is its density?

3

D = m = 21.7 g = 0.858 g/cm3

v

25.3 cm3

Density

○ Determined by dividing the mass by the

volume.

D- density (g/cm3)

m – mass (g)

V – volume (cm3 or liters)

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Unit 1 quiz - 10 multiple choice
on formative (20 minutes)

After Quiz:
percent error & density practice on GC
(pg 15-16 in workbook)

• read density of pennies lab intro pg 17 and design a procedure