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Grade 7 Science
Homogeneous &
Heterogeneous
Mixtures
Homogeneous Mixture
• also called
solutions
• can be solid,
liquid or gas
Stainless steel
• the particles
are evenly
mixed so that
none of the
original
substances are
visible
Kool-aid
• they appear
to be ONE
substance
• light passes
through
unaffected
Heterogeneous Mixtures
• also called
mechanical
mixtures
• can be solid,
liquid or gas
Granola bar
Concrete
• the different parts
are visible to the
eye (may need a
microscope)
• the particles do
not evenly mix
• Light will
reflect
perpendicular
to the
direction of
the beam
Student Activity...
• Create a chart and list the
various homogeneous and
heterogeneous mixtures in
your home.
• Share with your shoulder
partner and add to your list.
The Tyndall Effect
• A phenomenon that can be used
to distinguish between solutions
and what appears to be a
solution
• cannot be used to distinguish
between a solution and a pure
liquid
In a Solution...
• Light passes
unaffected (if a student
looks at the beaker
perpendicular to the
direction of thebeam
they will NOT see it
In a Mechanical Mixture...
• The light will scatter
as it passes through
the mixture because
all particles arenot
dissolved (as shown
on the left)
Both Hetero and
Homogenoeus Mixtures?
Complete Activity 7-1C
Page 238 & 239
Post Activity Discussion...
Enrichment
Colloids
Dispersions
Emulsions