The Colloid Connection
What is a colloid?
A heterogeneous mixture that
never settles.
Examples:
Aside from food products, are there
any other colloids we encounter?
Yes – both good and bad.
Let’s look at the good first…
When you turn on the faucet,
is the water clean or dirty?
Clean (we hope!) But why?
Colloids! But how?
Water is first taken from a stream, river, or
reservoir.
It then goes into a tank where LIME and
ALUM are added.
LIME
ALUM
The LIME and the ALUM form a
colloid that is a gel-like substance.
The gel-like substance traps
microorganisms and other particles.
The “dirty” gel then passes through fine
sand, where it is trapped.
Leaving…
Nice clean water.
Colloids aren’t always good though…
Pollution
Unburned particles
suspended in the air
Aka “soot”
On to our favorite colloid – gelatin (Jell-o)
Gelatin is large strands weakly
connected together.
When added to boiling water, the
strands split apart.
Water molecules get trapped between the
strands as the gelatin cools.
And the gelatin “hardens” into a
semisolid colloid.
Questions for Discussion
What does the hot water do to assist in
the formation of the colloid, gelatin?
It breaks the strands apart.
How does smoke fit the definition
of a colloid?
It contains carbon fragments that
do not settle out.