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,

where is the density is the mass is the volume

- the SI unit if density is -

- as “weight density”, it is expressed as

SPECIFIC GRAVITY- also known as “relative density”.- is the ratio of the density of the

substance to that of water - can be expressed by the equation

DENSITIES OF SOME COMMON SUBSTANCESAT STANDARD TEMPERATURE

SUBSTANCEAir

Aluminum

Benzene

Copper

Ethyl alcohol

Fresh water

Glycerin

Gold

Helium gas

Hydrogen gas

SUBSTANCEIce

Iron

Lead

Mercury

Oak

Oxygen gas

Pine

Platinum

Seawater

Silver

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 38.94 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.

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?