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