Grade 7 Science

1
Grade 7 Science

• Homogeneous
• Heterogeneous
• Mixtures

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Homogeneous Mixture

• also called solutions
• can be solid, liquid or gas

Stainless steel
3

• the particles are evenly mixed so that none of
  the original substances are visible

Kool-aid
4

• they appear to be ONE substance
• light passes through unaffected

5
Heterogeneous Mixtures

• also called mechanical mixtures
• can be solid, liquid or gas

Granola bar
6

• the different parts are visible to the eye (may
  need a microscope)
• the particles do not evenly mix

Concrete
7

• Light will reflect perpendicular to the direction
  of the beam

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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.

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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

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In a Solution...

• Light passes unaffected (if a student looks at
  the beaker perpendicular to the direction of the
  beam they will NOT see it

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In a Mechanical Mixture...

• The light will scatter as it passes through the
  mixture because all particles are not dissolved
  (as shown on the left)

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Both Hetero and Homogenoeus Mixtures?
Complete Activity 7-1C Page 238 239
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Post Activity Discussion...

• Enrichment

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Colloids
15
Dispersions
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Emulsions