Mixtures and

solutionsMR. BANKS

7TH GRADE SCIENCE

Mixtures

A mixture is a physical

blend of two or more

substances.

These substances can be

atoms and/or compounds.

Unlike a compound, the

atoms in mixtures are not

bonded together.

Mixtures

Mixtures can exist as

solids, liquids, or gasses.

Mixtures

Mixtures are made by

combining together two

or more substances that

don’t react.

Each part of a mixture

keeps its own properties.

The substances in a

mixture don’t react with

one another.

Mixtures

There are two types of

mixtures.

Homogeneous

Heterogeneous

Mixtures

Heterogeneous mixtures

are mixtures where the

substances that make

them are not evenly

distributed.

Usually there are mixtures

of two solids.

Mixtures

Homogeneous mixtures

are mixtures where the

materials are evenly

distributed throughout.

English lesson!

The prefix “homo” means

“same”

If you take a sample from

any part of the mixture it

will be exactly the same

as any other part.

The prefix “hetero” means

“different”

If you take a sample from

a part of the mixture it will

look different from

another part.

Heterogeneous vs Homogeneous

What is it?

Cheerios

Homogeneous

What is it?

Trail Mix

Heterogeneous

What is it?

Kool - Aid

Homogeneous

What is it?

Water

Homogeneous

What is it?

White Vinegar

Homogeneous

What is it?

Italian Salad Dressing

Heterogeneous

Raisin Bran

Orange juice

Air

Chunky Soup

Hamburger

Cake Batter

Paint

Salad

Rock

Answers:

Raisin Bran – heterogeneous

Orange Juice – homogeneous

Air – heterogeneous

Chunky Soup – heterogeneous

Hamburger – heterogeneous

Cake Batter – homogeneous

Paint – homogeneous

Salad – heterogeneous

Mineral Rock - heterogeneous

Solutions

Solutions are mixtures that

consist of microscopic

particles.

Solutions are formed when

one substance dissolves in

another.

Solutions are almost always

homogeneous mixtures.

Solutions are always liquids

after the substance has

dissolved.

Solutions

A solution always has a substance that is

dissolved and a substance that does the

dissolving.

The substance that is dissolved is the solute.

The substance that does the dissolving is the

solvent.

Kool-aid Mix(solute)

Water(solvent)

Kool-aid(solution)

Separating mixtures

When two or more

substances are mixed.

They are combined, but

do not chemically

change or bond.

They retain their normal

properties.

This means that all

mixtures CAN be

separated.

Separating mixtures

Hand separation – basically using your hands to

separate things.

Only possible when the things mixed are large,

can be picked up, and can be distinguished by

sight.

Separating mixtures

Magnetic attraction – if one of the substances in

the mixture is made of a magnetic metal you can

use a magnet to separate that part out.

Useful for separating things made of iron from

other materials.

Separating mixtures

Filtration – useful for

separating solids from

liquids, or larger solids

from smaller solids.

Involves passing the

mixture through a porous

material (a material with

holes).

Fluid and smaller solids will

pass through, but not the

larger solids.

Separating mixtures

Settling – sometimes mixtures

will separate themselves out

over time just due to the

materials having different

densities.

Useful for separating liquids

from solids or liquids with

different densities from each

other.

Separating mixtures

Evaporation – By

heating a liquid

mixture up, the liquid

will evaporate

leaving behind the

solids and substances

that were dissolved in

the liquid.

Useful for separating

solutions.

Separating mixtures

Chromatography – used

to separate different

dissolved substances in a

solution from one another.

Using properties like

electric charge, size, and

how easily things dissolve,

the materials can be

separated.

Chromatography

Chromatography

Separating mixtures

There are many other ways to separate mixtures.

Many of which combine multiple of these

strategies to do it.

Solutions

Solutions are mixtures that

consist of microscopic

particles.

Solutions are formed when

one substance dissolves in

another.

Solutions are almost always

homogeneous mixtures.

Solutions are always liquids

after the substance has

dissolved.

Solutions

A solution always has a substance that is

dissolved and a substance that does the

dissolving.

The substance that is dissolved is the solute.

The substance that does the dissolving is the

solvent.

Kool-aid Mix(solute)

Water(solvent)

Kool-aid(solution)

Solubility

The ability of one

substance to dissolve in

another substance is its

solubility.

There is a limit to how

much solute a solvent

can dissolve.

Solubility

Solubility can be changed dramatically by

changing the temperature of the solvent.

For solid solutes, more solute will dissolve as the

temperature of the solvent goes up.

Solubility graphs

Solubility graphs show how much of a solute will

dissolve in a solvent at a given temperature.

Potassium chloride (solute) in vinegar (solvent)

Solubility graphs

When there is less solute dissolved than a solvent

can hold it is known as an unsaturated solution.

Potassium chloride (solute) in vinegar (solvent)

Solubility graphs

When there is the maximum dissolved for a

specific temperature it is a saturated solution.

Potassium chloride (solute) in vinegar (solvent)

Solubility graphs

When there is more solute dissolved then it is

known as a supersaturated solution.

Potassium chloride (solute) in vinegar (solvent)

Solubility graphs

Supersaturated solutions are made when solute is

dissolved in a heated solvent that is then cooled.

Potassium chloride (solute) in vinegar (solvent)

Supersaturated solutions

Supersaturated solutions are very unstable and

the solute often “falls out” of solution and reforms

crystals. The crystals form on the surfaces of other

crystals or objects in the solution.

Solubility rate

The speed at which

something can dissolve

can also be changed.

Temperature

Mixing

Surface area

• Potassium nitrate

• Sodium nitrate

• Sodium Chloride

Separating mixtures

Extraction – if you have a

substance that can be

dissolved and one that

can’t you can separate

them by dissolving the

one that can be dissolved

and then filtering what’s

left.

Water

Water is known as the

“universal solvent” since

many, many materials

can be dissolved in

water.

Ocean water is basically

a solution of salt in water.

Body fluids are also water

solutions.

Separating Mixtures

Suppose you had a mixture of iron nails, salt and

water…

How would you separate this mixture completely?

Based on which physical properties would you

base your method on?

Separating Mixtures

How would you separate the components in tap

water?

Distillation

A liquid is boiled to produce vapor that is then

condensed again to a liquid

Separating Mixtures

Mixtures

Sample problem

How can a mixture of iron fillings and

aluminum fillings be separated?

1.-Analyze: Plan a problem solving strategy

List the properties of iron and aluminum and

look for something that would be useful in

separating the mixture

Mixtures

Iron:

Metal

Grayish

Not soluble in water

Attracted to a

magnet

Aluminum:

Metal

Grayish

Not soluble in water

Not attracted to

magnets

2.- Solve: Apply the problem-solving strategy.

Make use of a property that differentiates the

metals; use a magnet to attract the iron fillings.

Mixtures

3.-Evaluate: Does the result make

sense?

Because the magnet attracts iron

but not aluminum filings, the iron

would be removed while the

aluminum would be left behind.

Practice Problems

What physical properties could be used to separate iron filings from salt?

Which of the following are homogenous? heterogenous?

1.-Spaghetti sauce 4.-Cough syrup

2.-Glass 5.-Mixture of nitrogen gas

3.-Muddy Water and helium gas