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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
Volume vs. Mass
Volume is the amount of space something takes up
Mass is the amount of matter in an object (how “heavy” something is)
Finding Volume of a Regular Shape
An object with a “regular” shape is measurable and symmetric
1.Measure length (L), width (W) and height (H)
2.Multiply L x W x H3.Make sure units make sense (cm3, m3)
4 cm x 6 cm x 5 cm = 120 cm3
Conversion Factor: 1 cm3 = 1mL
Finding Volume of an Irregular Shape
An object that can not easily be measured
1.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
• 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/mLDepends on the units used
for mass and volume
Density of Phases of MatterWhich phase of matter is the densest?
Which phase of matter is the least dense?
*Usually the solid phase of a substance will sink in it’s liquid phase because it is more dense• Water is an
exception!• Because water
expands when it freezes, solid water (ice) is actually less dense than liquid water
SOLID
GAS
SolidsBone 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
Densities of Common Substances (g/mL)
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 it’s shape or sizei.e. the density of pure water is always 1 g/mL
Finding Density
Formula:
M = mass
V= volume
D = density
D = M / V
M = D x V
V = M / D
Density (D) is mass (m) per unit volume (v)per = divided byD = m/v (m ÷ v)
Divided by Multiplied by
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
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
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