HETEROGENEOUS AQUEOUS SYSTEMS

Chapter 15.3

OBJECTIVE

• I will be able to distinguish between suspensions, solutions, and colloids

SUSPENSIONS

• Definition: A heterogenepous mixture from which particles settle out upon standing

– Particles are larger (greater than 1000nm)

– Particles don’t stay suspended forever

COLLOIDS

• Definition: A heterogeneous mixture containing particles that range in size from 1nm to 1000 nm– Particles spread throughout the dispersion

medium (solid/liquid/gas)– Examples: glue, paint, gelatin aerosol sprays,

milk, smoke

• Biggest difference between all three is size of particles

– Solutions and colloids both appear to be uniform throughout, however particle size is different

– Suspensions and colloids can both be cloudy/milky in appearance, however particle size is different

COLLOIDS

• Distinguishing Colloids

1.

2.

3.

4.

COLLOIDS

• ________________

– The scattering of visible light by colloidal particles

COLLOIDS

• ________________– Chaotic movement of colloidal particles

• Under the microscope, flashes of light (scintillations) are seen due to the reflecting and scattering of the light by particle movement– Colloid particles collide with molecules

which keeps particles from settling out

COLLOIDS

• ________________

– Destroying a colloidal system by adding ions with opposite charges of the colloidal particles

• Colloidal particles can adsorb (hold on its surface) ions and take their charge

• This keeps colloidal particles suspended because like charges repel

COLLOIDS

• ________________

– Colloidal dispersion of a liquid in a liquid

• Examples:

– Soap and detergent

– Butter/margarine

– Mayonnaise

COLLOIDS