1. Density

2. Comparing Feathers and Rocks
Which do you think would have the greater mass?
Which do you think would have the greater volume?
1 kg of feathers
1 kg of rock

3. Density Density is defined as mass per unit volume.
Density is a measure of how tightly packed molecules are in an object.
Basically, it is the amount of matter within a certain volume.
Density is the amount of matter within a certain volume.

4. The Math… The Units: Mass = Grams (g) Volume (2 ways) Density (2 ways)
Ruler = cm3
Displacement = ml
Density (2 ways)
Ruler = g/cm3
Displacement = g/ml

5. IRON! It has the most mass for that volume.
What is Density?
If you take the same volume of different substances, then
they will weigh different amounts.
Water
Iron
Wood
1 cm3
0.50 g
1.00 g
8.00 g
Q) Which of these is most dense? Why?
IRON! It has the most mass for that volume.

6. Density for different things…
Substance
Density (g/cm3)
Hydrogen
Helium
Air (atmospheric air)
Carbon Monoxide
Carbon Dioxide
Gasoline
0.70
Ice
0.922
Water 20deg C)
0.998
Water 4deg C)
1.000
Milk
1.03
Magnesium
1.07
Water in the Dead Sea
(31.5% salt in the water)
1.24
Aluminum
2.7
Iron
7.8
Lead
11.3
Mercury
13.6
Gold
19.3
21.4
Each substance has it’s
own density.
It does not matter how
much of a substance you
have, it will have the same
density.
1 gram of water will have the
same density as 100 grams
of water
Distilled Water has a density
of 1 g/cm3
(This is the only density you need to memorize!)

7. Density for different things…
Substance
Density (g/cm3)
Hydrogen
Helium
Air (atmospheric air)
Carbon Monoxide
Carbon Dioxide
Gasoline
0.70
Ice
0.922
Water 20deg C)
0.998
Water 4deg C)
1.000
Milk
1.03
Magnesium
1.07
Water in the Dead Sea
(31.5% salt in the water)
1.24
Aluminum
2.7
Iron
7.8
Lead
11.3
Mercury
13.6
Gold
19.3
21.4
Objects with different densities
interact in a very predictable way
The more dense object will sink, the
less dense will rise to the top…

8. Different objects have different densities
Is the ice or the water more dense?
The water is more dense than the ice because the ice floats!
Objects with less than 1 g/cm3 density will float in tap water (ex: ice at 0.93)
Objects with more than 1 g/cm3 density will sink in tap water (ex: gold at 19.3)

9. Sidenote…
Sulfur hexaflouride. Density? Explain this.

10. The Math… The Units: Mass = Grams (g) Volume (2 ways) Density (2 ways)
Ruler = cm3
Displacement = ml
Density (2 ways)
Ruler = g/cm3
Displacement = g/ml

11. Find the mass of the object
Determining Density
Step 1:
Find the mass of the object

12. Determining Density STEP 2: Determine Volume
We have 2 ways to determine VOLUME.
Measure
Cube = L * W * H
Cylinder = Πr2H
Sphere = (4Πr3)/3
Calculate Displacement
Displacement is how much liquid is moved out of the way to make room for the object placed in water

13. Determining Volume: Displacement
Calculate Displacement
Displacement is how much liquid is moved out of the way to make room for the object placed in water

14. Determining Density Step 3: Calculate Density = Mass Volume Units:
For ruler: g/cm3
For displacement: g/ml

15. To find density:
Find the mass of the object
Find the volume of the object
Divide : Density = Mass / Volume
Ex. If the mass of an object is 35 grams and it takes up 7 cm3 of space, calculate the density.

16. To find density:
Find the mass of the object
Find the volume of the object
Divide : Density = Mass / Volume
Ex. If the mass of an object is 35 grams and it takes up 7 cm3 of space, calculate the density.
Set up your density problems like this:
Known: Mass = 35 grams Unknown: Density (g/cm3) Volume = 7 cm3
Formula: D = M / V Solution: D = 35g / 7cm3
D = 5g/cm3

17. Practice Problem 1 Osmium is a very dense metal. What is its
density in g/cm3 if g of the metal occupies
a volume of 2.22cm3?
1) g/cm3
2) 22.5 g/cm3
3) 111 g/cm3

18. Practice Problem #3
What is the density (g/cm3) of 48 g of a metal if the metal raises the level of water in a graduated cylinder from 25 mL to 33 mL?
A) 0.2 g/ cm B) 6 g/cm3 C) g/cm3
25 ml mL
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