Separating Mixtures
http://www.youtube.com/watch?v=jWdu_RVy5_A
• The components of a mixture can be separated
based on the physical properties of:
– Magnetism
– Density
• An instrument that uses this property to separate
mixtures when tiny solid particles are dissolved in a liquid
is called a centrifuge.
• Some techniques used to separate the
components of a mixture are:
– Filtration
• used to separate liquids from solids
– Evaporation or distillation
• used to separate solutions
Episode 203
Density
• Mass per unit volume
– Per means “divide”
• Density = mass/volume
• Common units for
density:
– g/mL
– g/cm3
Episode 203
Suppose we have an object with a mass of 5.0
grams ans a volume of 2.0 mL. What would the
density of this object?
5.0 grams
2.0 mL
2.5 grams/mL
Episode 203
Problem Set One
• Given a mass of 12 g and a volume of 3 mL,
calculate the density.
12 grams
3 mL
= 4 grams/mL
• What is the mass of 50 mL of water?
(Density of water is 1 g/mL)
m = Dv
1 g/mL x 50 mL
= 50 grams
• Given that the density of iron is 7.9 g/cm3,
what would be the volume of a 15.8 g piece of
iron?
v = m/D
15.8 grams
7.9
g/cm3
= 2.0 cm3
Episode 203
Problem Set Two
• Find the density of a block with a length of 4.0 cm, a width of
3.0 cm, a height of 2.0 cm, and a mass of 36 grams.
36 grams
4.0cm x 3.0cm x 2.0 cm
= 1.5 grams/cm3
• Find the density of an 8.0 g rock if the water in a graduated
cylinder rises from 20.0 mL to 23.5 mL when the rock is placed
into the cylinder.
8.0 grams
23.5mL – 20.0mL
= 2.3 grams/mL
• You have a piece of silver with a mass of 31.5 g. Silver has a
density of 10.5 g/cm3. What would be the new level of water if
this piece of silver is placed into 15 mL of water?
v = m/D
31.5 grams
10.5 g/cm3
= 3.00 cm3 or 3.00 mL
15 mL + 3.0 mL = 18mL
Episode 203