Title: Density
1Density
2Which do you think would have the greater mass?
Greater volume? Why?
- Same mass!
- Smaller volume
3Volume vs. Mass
- Mass
- is the amount of matter in an object (how heavy
something is)
- Volume
- is the amount of space something takes up
4Finding Mass
- Place the object on a scale or balance
- Units should be grams (g) or kilograms (kg)
5Finding Volume of a Regular Shape
- An object with a regular shape is measurable
and symmetric - Measure length (L), width (W) and height (H)
- Multiply L x W x H
- Make sure units make sense (cm3, m3)
- 4 cm x 6 cm x 5 cm 120 cm3
Conversion Factor 1 cm3 1mL
6Finding Volume of an Irregular Shape
- An object that can not easily be measured
- Use displacement
- Fill a graduated cylinder or overflow can with
water - Measure how much water goes up/spills out when
object is placed in water
Remember 1 cm3 1mL
7DENSITY
- Density is defined as mass per unit volume. It
is a measure of how tightly packed and how heavy
the molecules are in an object. - Density is the amount of matter within a certain
volume (how much stuff is crammed into
something)
Units of Density g/cm3 or g/mL Depends on
the units used for mass and volume
8Density of Phases of Matter
Which phase of matter is the densest? Which
phase of matter is the least dense? Usually the
solid phase of a substance will sink in its
liquid phase because it is more dense
SOLID
GAS
- Water is an exception!
- Because water expands when it freezes, solid
water (ice) is actually less dense than liquid
water
9Densities of Common Substances (g/mL)
- Solids
- Bone 2
- Brick 1.8
- Cork 0.2
- Ice 0.92
- Marble 2.7
- Paraffin 0.9
- Rubber 1.2
- Bamboo 0.3
- Oak Wood 0.7
- Pine Wood 0.6
Metals Aluminum 2.7 Copper 8.9 Gold 19.3 Iron 7
.8 Lead 11.3 Silver 10.5
Liquids Pure Water 1.0 Sea Water 1.03 Alcohol 0.8
Gylcerine 1.3 Milk 1.03 Turpentine 0.9 Mercury 13
.6 Gasoline 0.7
Note The density of a substance will always be
the same, regardless of its shape or size i.e.
the density of pure water is always 1 g/mL
10Finding Density
Density (D) is mass (m) per unit volume (v) per
divided by D m/v (m v)
Formula
D M / V M D x V
V M / D
M mass V volume D density
Divided by
Multiplied by
11Practice Problem 1
If the mass of an object is 35 grams and it takes
up 7 cm3 of space, calculate the density.
Given Mass 35 grams Volume 7 cm3 Density
? (g/ cm3)
Formula D M / V Solution D 35 g / 7
cm3 D 5 g/cm3
12Practice Problem 2
A rectangular block of copper metal has a mass of
1896 g. The dimensions of the block are 8.4 cm by
5.5 cm by 4.6 cm. From this data, what is the
density of copper?
Given M 1896 grams V 8.4 cm x 5.5 cm x 4.6
cm 212.52 cm3 D ? (g/ cm3)
Formula D M / V Solution D 1896 g /
212.52 cm3 D 8.92 g/cm3
13Practice Problem 3
Find the mass of 250.0 mL of benzene. The density
of benzene is 0.8765 g/mL.
Given V 250.0 mL D 0.8765 g/mL M ? g
Formula M D x V Solution M 0.8765 g/
mL x 250.0 mL M 219.13 g
14Practice Problem 4
What volume of silver metal will has a mass of
exactly 2500.0 g. The density of silver is 10.5
g/cm3.
Given M 2500.0 g D 10.5 g/cm3 V ?
cm3
Formula V M / D Solution V 2500.0 g /
10.5 g/cm3 V 238.10 cm3