The document discusses density and specific gravity. It defines density as the ratio of mass to volume and gives the equation ρ = m/v. Specific gravity is defined as the ratio of a substance's density to that of water. Example densities are given for common substances like air, water, gold and others. Sample problems demonstrate calculating density, mass, volume and specific gravity using the relevant equations and given values.

1. Lecture #1 – June 11, 2014
DENSITY
- is a scalar quantity and defined as the ratio
of mass per unit volume.
- it is also known as mass density.
- in equation,
ρ =
𝑚
𝑣
(𝑒𝑞. 1)
where 𝜌 is the density
𝑚 is the mass
𝑣 is the volume

2. - the SI unit if density is
𝑘𝑔
𝑚3 .
- 1
𝑔
𝑐𝑚3 = 10
𝑘𝑔
𝑚3
- as “weight density”, it is expressed as
𝜌 =
𝑊
𝑣
=
𝑚𝑔
𝑣
(𝑒𝑞. 2)

3. SPECIFIC GRAVITY
- also known as “relative density”.
- is the ratio of the density of the
substance to that of water 1000
𝑘𝑔
𝑚3
- can be expressed by the equation
𝑆 𝑔 =
𝜌𝑠𝑢𝑏𝑠𝑡𝑎𝑛𝑐𝑒
𝜌 𝑤𝑎𝑡𝑒𝑟
(𝑒𝑞. 3)

4. DENSITIES OF SOME COMMON SUBSTANCESAT
STANDARD TEMPERATURE 𝟎°
𝑪
SUBSTANCE 𝝆
𝒌𝒈
𝒎 𝟑
Air 𝟏. 𝟐𝟗
Aluminum 𝟐. 𝟕𝟎 × 𝟏𝟎 𝟑
Benzene 𝟎. 𝟖𝟕𝟗 × 𝟏𝟎 𝟑
Copper 𝟖. 𝟗𝟐 × 𝟏𝟎 𝟑
Ethyl alcohol 𝟎. 𝟖𝟎𝟔 × 𝟏𝟎 𝟑
Fresh water 𝟏. 𝟎𝟎 × 𝟏𝟎 𝟑
Glycerin 𝟏. 𝟐𝟔 × 𝟏𝟎 𝟑
Gold 𝟏𝟗. 𝟑 × 𝟏𝟎 𝟑
Helium gas 𝟏. 𝟕𝟗 × 𝟏𝟎−𝟏
Hydrogen gas 𝟖. 𝟗𝟗 × 𝟏𝟎−𝟐

5. SUBSTANCE 𝝆
𝒌𝒈
𝒎 𝟑
Ice 𝟎. 𝟗𝟏𝟕 × 𝟏𝟎 𝟑
Iron 𝟕. 𝟖𝟔 × 𝟏𝟎 𝟑
Lead 𝟏𝟏. 𝟑 × 𝟏𝟎 𝟑
Mercury 𝟏𝟑. 𝟔 × 𝟏𝟎 𝟑
Oak 𝟎. 𝟕𝟏𝟎 × 𝟏𝟎 𝟑
Oxygen gas 𝟏. 𝟒𝟑
Pine 𝟎. 𝟑𝟕𝟑 × 𝟏𝟎 𝟑
Platinum 𝟐𝟏. 𝟒 × 𝟏𝟎 𝟑
Seawater 𝟏. 𝟎𝟑 × 𝟏𝟎 𝟑
Silver 𝟏𝟎. 𝟓 × 𝟏𝟎 𝟑

6. Sample Problem
1. What is the mass of solid iron wrecking ball of radius
18cm?
2. A lead cube has a total mass of 50kg. What is the
length of a side of a cube and the volume of a cube?
3. A rectangular block measures 2.3cm x 5.1cm x 7.8cm.
It has a mass of 66g.
4. Calculate the density and specific gravity of a liquid if
38.94𝑐𝑚3 of that liquid has a mass of 34.8g.
5. What volume of ethyl alcohol has a weight of 125.0g.
The specific gravity of alcohol is 0.791.

7. Seatwork #1 – June 11, 2014
1. Find the mass and weight of the air in a living room
with a 4.00m x 5.00m floor and a ceiling of 3.00m
high. What is the mass and weight of an equal volume
of water?
2. The mattress of water bed is 2.00m long by 2.00m
wide and 3.0cm deep. Find the weight of the water in
the mattress.
3. You purchase a rectangular piece of metal that has
dimensions 5.0mm x 15.0mm x 3.00mm and a mass
of 0.0158kg. The seller tells you that the metal is gold.
To check this, you compute the average density of the
piece. What value do you get? Were you cheated?