HETEROGENEOUS

1. HETEROGENOUS
SUSPPENSIONS AND COLLOIDS

2. RECAP

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Suspensions
Suspensions
What is the difference between a suspension and a solution?
• A suspension ….

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Suspensions
Suspensions
What is the difference between a suspension and a solution?
• A suspension is a mixture from which
particles settle out upon standing.

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A suspension differs from a solution
because the particles of a suspension
are much larger and do not stay
suspended indefinitely.
Suspensions

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A suspension differs from a solution because
the particles of a suspension are much larger
and do not stay suspended indefinitely.
Suspensions
• The particles in a typical suspension have
an average diameter greater than 1000 nm.
• By contrast, the particle size in a solution is
usually about 1 nm.

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Suspensions
•A solution is a homogeneous mixture.
•Suspensions are heterogeneous
because at least two substances can be
clearly identified.

9. Suspensions
The difference between a solution and suspension is easily
seen when the type of mixture is filtered.
The small size of the
solute particles in a
solution allows them to
pass through filter paper.
The particles of a
suspension can be
removed by filtration.

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Explain why a mixture of sand and water can
be separated by filtration, but a mixture of
salt and water cannot.

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Explain why a mixture of sand and water can be separated by filtration,
but a mixture of salt and water cannot.
A mixture of sand and water is a suspension,
and a mixture of salt and water is a solution.
The particles in the sand mixture are much
larger than the ions in the salt mixture. The
sand particles are too large to pass through
filter paper; the ions are not.

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Colloids
Colloids
What distinguishes a colloid from a
suspension and a solution?

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Colloids
A colloid is a heterogeneous mixture
containing particles that range in size
from 1 nm to 1000 nm.
•The particles are spread, or dispersed, throughout
the dispersion medium, which can be a solid,
liquid, or gas.

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Colloids
The first substances to be identified as
colloids were glues.
Some Colloidal Systems
System
Type Example
Dispersed
phase
Dispersion
medium
Gas Liquid Foam Whipped cream
Gas Solid Foam Marshmallow
Liquid Liquid Emulsion Milk, mayonnaise
Liquid Gas Aerosol Fog, aerosol
Solid Gas Smoke Dust in air
Solid Liquid Sols, gels
Egg white, jelly, paint, blood,
starch in water, gelatin

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Colloids
Colloids have particles smaller than
those in suspensions and larger than
those in solutions.

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Colloids
Colloids have particles smaller than those in suspensions and
larger than those in solutions.
• These intermediate-sized particles cannot
be retained by filter paper as are the
larger particles of a suspension.
• They do not settle out with time.

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Colloids
The Tyndall Effect
You cannot see a beam of sunlight unless the light passes through
particles of water (mist) or dust in the air.
• These particles scatter the sunlight.
• Similarly, a beam of light is visible as it
passes through a colloid.

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Colloids
The Tyndall Effect
The scattering of visible light by colloidal particles is called theTyndall
effect.
Flashlight
Solution Colloid Suspension

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Colloids
• Suspensions also exhibit theTyndall effect.
• The particles in solutions are too small to scatter light.
Flashlight
Solution Colloid Suspension

20. ColloidsThis table summarizes the properties of solutions,
colloids, and suspensions.
Properties of Solutions, Colloids, and Suspensions
Property
System
Solution Colloid Suspension
Particle type
Ions, atoms, small
molecules
Large molecules or
particles
Large particles or
aggregates
Particle size 0.1–1 nm 1–1000 nm 1000 nm and larger
Effect of light No scattering Exhibits Tyndall effect Exhibits Tyndall effect
Effect of gravity
Stable, does not
separate
Stable, does not separate Unstable, sediment forms
Filtration
Particles not
retained on filter
Particles not retained on
filter
Particles retained on filter
Uniformity Homogeneous Heterogeneous Heterogeneous

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KeyConcepts
 A suspension differs from a solution
because the particles of a suspension are
much larger and do not stay suspended
indefinitely.
 Colloids have particles smaller than
those in suspensions and larger than
those in solutions.
KEY CONCEPTS