Measurement

I. Units of Measurement Number vs. Quantity

SI Base Units & Prefixes

Derived Units

Density Calculations

A. Number vs. Quantity

Quantity - number + unit

UNITS MATTER!!

B. SI Units

Quantity Base Unit Symbol

Length

Mass

Time

Temp

meter

kilogram

second

kelvin

m

kg

s

K

Current ampere A

B. SI Units

mega- M 106

deci- d 10-1

centi- c 10-2

milli- m 10-3

Prefix Symbol Factor

micro- 10-6

nano- n 10-9

pico- p 10-12

kilo- k 103

C. Derived Units

Combination of base units. Volume - length length length

1 cm3 = 1 mL 1 dm3 = 1 L Density - mass per unit volume (g/cm3)

D = MV D

M

V

D. 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

M = (13.6 g/cm3)(825cm3)

M = 11,220 g

DM

V

D. Density

1) 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

DM

V

WORK:

V = M D

V = 25 g

0.87 g/mL

V = 28.7 mL

D. Density

2) 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 = ?

DM

V

WORK:

D = M V

D = 620 g

753 cm3

D = 0.82 g/cm3