Separating Mixtures

• 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

http://www.youtube.com/watch?v=jWdu_RVy5_A

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.

• What is the mass of 50 mL of water? (Density of water is 1 g/mL)

• Given that the density of iron is 7.9 g/cm3, what would be the volume of a 15.8 g piece of iron?

12 grams3

mL

= 4 grams/mL

m = Dv

1 g/mL x 50 mL = 50 grams

v = m/D

15.8 grams7.9 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.

• 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.

• 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?

36 grams

4.0cm x 3.0cm x 2.0 cm

= 1.5 grams/cm3

= 2.3 grams/mL

v = m/D

31.5 grams10.5 g/cm3

= 3.00 cm3 or 3.00 mL

8.0 grams

23.5mL – 20.0mL

15 mL + 3.0 mL = 18mL

Episode 203