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Chemistry Notes
Unit 2: Density
Objectives

Define density in terms of




Identify Units for density
Calculate density


Mass and volume
Packing of particles
Calculate mass or volume given density
Determine density in a laboratory
Density
Recall:
 Mass – amount of matter in an object (g)
 Volume – the amount of space an object
takes up (ml)
Density
Density = mass per unit volume
 Density is a derived unit
 Densities of materials can change with
temperature
 Examples of units for density


g/cm3, kg/m3, g/mL, kg/L
Equation for Density
D=m/V
Density

Both blocks have the same volume, which
has a higher density? Why?
Density
Measuring Density
 Find mass on a balance or scale, calculate
volume


(4/3 π r2, l X w X h, etc.)  divide mass by
volume  density
Find mass on a balance or scale, the volume
can be measured using water displacement

 divide mass by volume  density

LAB Method: Using the water displacement method
to find volume of an irregular object
1. put object into a graduated cylinder with 50mL of
water (or other set value)
2. object raises the water level by so many mL’s
3. Subtract 50 (or other original amount) from the new
value observed on the graduated cylinder (e.g. 55 mL)
4. volume of the object is the difference between initial
and final values on the graduated cylinder
Final Volume – Initial Volume = Net Volume
23 mL
–
20 mL
= 3 mL
Volume of the rock is 3 mL
Density
Solving for mass given the density
 Calculate the mass of Object B
(D = 2.164 g/cm3, v = 300 cm3)
 Start with equation; D = m / v
 Plug in known quantities;
2.164 g/cm3 = m / (300 cm3)
 Solve: Answer 649.2 g
Density
Solving for volume given density
 Calculate the volume of Object C
(D = 1.87 g/cm3, m = 600g)
 Start with equation; D = m / v
 Plug in known quantities;
1.87 g/cm3 = (600 g) / v
 Solve: Answer 320.86 cm3
Density

Density is the
measure of particles
per unit volume.

Density can describe
states of matter
Density

Allows us to identify pure substances
TABLE 1 - Densities of Common Substances
Substance
Density (g/cm3)
Substance
Density (g/cm3)
Helium (gas)
0.0001663
Zinc (solid)
7.13
Oxygen (gas)
0.001331
Silver (solid)
10.50
Water (liquid)
1.00
Lead (solid)
11.35
Pyrite (solid)
5.02
Mercury (liquid)
13.55