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Density

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Density Which do you think would have the greater mass? Greater volume? Why? 1 kg of feathers 1 kg of rock Same mass! Larger volume Same mass! – PowerPoint PPT presentation

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Title: Density


1
Density
2
Which do you think would have the greater mass?
Greater volume? Why?
  • 1 kg of feathers
  • 1 kg of rock
  • Same mass!
  • Larger volume
  • Same mass!
  • Smaller volume

3
Volume vs. Mass
  • Mass
  • is the amount of matter in an object (how heavy
    something is)
  • Volume
  • is the amount of space something takes up

4
Finding Mass
  • Place the object on a scale or balance
  • Units should be grams (g) or kilograms (kg)

5
Finding 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
6
Finding 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
7
DENSITY
  • 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
8
Density 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

9
Densities 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
10
Finding 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
11
Practice 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
12
Practice 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
13
Practice 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
14
Practice 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
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