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
• the different parts are visible to the eye (may need a microscope)
• the particles do not evenly mixConcrete
• 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 the beam they will NOT see it
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)
Both Hetero and Homogenoeus Mixtures?
Complete Activity 7-1C
Page 238 & 239
Post Activity Discussion...
Enrichment
Colloids
Dispersions
Emulsions