Density WarmUp Questions

1
Density Warm-Up Questions

• If you have one pound of feathers and one pound
  of bricks, do they weigh the same? Why or why
  not?
• Yes, because they have the same weight (1 pound)
• What are the SI units of mass?
• Kilograms
• What piece of lab equipment do you use to measure
  volume?
• Graduated cylinder

2
A Bit More about Density

• Pre-Lab Discussion
• All That Glitters

3
Density

• Density is a quantity that relates the mass and
  volume of a substance. It tells how much stuff is
  in a certain space (how cramped the molecules
  are).
• Density mass volume
• (g/mL) (g) (mL)
• Example What is the density of a piece of steel
  that has a mass of 50 g and a volume of 25 mL?
• Density 50 g 25 mL 2 g/mL

4
Mass and Volume

• In order to have an understanding of density, we
  should first understand the quantities
• MASS
• The amount of matter (or stuff) in an object or
  substance
• Measured with a scale or balance (units are
  kilograms)
• VOLUME
• The amount of space occupied by an object or
  substance
• Measured with a graduated cylinder (units are mL
  or cm3)

5
Density of Various Substances

• Density is a characteristic (or property) of the
  substance, and does not depend on the size or
  shape. Some densities of common metals are given
  below

6
The Density of Copper

• From the previous table, we saw that the density
  of copper is 9.0 g/mL.
• What does this mean?
• Well, if we have a piece of copper that has a
  mass of 18.0 grams, it must have a volume of 2.0
  mL.
• Density mass volume
• volume mass density
• volume 18.0 g 9.0 g/mL
  2.0 mL

7
The Density of Copper

• But, what if we cut that piece of copper in half,
  so its new mass is 9.0 g and its new volume is
  1.0 mL. What is its density?
• Density mass volume
• Density 9.0 g 1.0 mL 9.0 g/mL STILL!!!
• DENSITY DOES NOT DEPEND ON SIZE OR SHAPE, ONLY ON
  THE SUBSTANCE ITSELF.
• Therefore, we can use density to identify
  substances

8
All That Glitters Lab

• Today we will calculate the densities of three
  pieces of metal. For each piece of metal, you
  will
• Measure mass of metal
• Measure volume of metal (using volume
  displacement)
• Calculate density
• Identify what types of metal we used

9
All That Glitters Data Table

• Your data table will look like this

10
Using the Golden Pennies

• As a last step, you will calculate the density of
  the penny we made golden in the previous lab.
• You will use this density to determine if the
  penny is really gold.

11
What you are to do

• Take the measurements given in the directions of
  the lab.
• Answer all questions (1-9) in complete
  sentences.
• Turn in the lab with your name on it! (one per
  person, NOT ONE PER GROUP)
• Begin homework Density calculations
• TONIGHT Please print the Unit 1 Review from the
  website.