Experiment: using the tyndall effect to identify colloids
these supplies are needed:
3 clear glasses with smooth sides
laser pointer or flashlight
red jell-o®
red food coloring
sugar
water
procedure:
using the regular recipe, mix up the jell-o® and fill one glass with the mixture. let the jell-o® chill until it gels. fill another glass with water and let it settle until the air bubbles disperse. fill the third glass with water and add 2 drops of food coloring and two tablespoons of sugar. stir until you are sure the sugar is completely dissolved.
when all three glasses are ready, line them up in any order and shine the laser (or flashlight) through all three glasses at the same time.
answer these questions:
what did you observe?
what is the tyndall effect?
which glass displayed the tyndall effect?
what does that tell you about the substance in the glass?
which glass represents a pure substance?
which glass represents a solution?

What did you observe?

When the mixture of Jell-O is shined with the light you observe that the mixture becomes opaque or misty.

In the other two glasses the mixture remains clear

The Jell-O mixture dispereses the light while the other two glasses let the light pass through them.

What is the Tyndall effect?

The Tyndall effect is the dispersion of light by colloid particles. This happens becasue colloid particles present in the mixture are bigger than solvated particles.

Colloid particles are so small that they cannot be in the mixture, but are big enough to disperse the light.

Which glass displayed the Tyndall effect?

The glass with the Jell-O displayed the Tyndall effect.

What does that tell you about the substance in the glass?

The mixture of this glass is a colloid, because they are the only mixtures that may look clear but becomes misty when the light passes trhough them.

Which glass represents a pure substance?

Only the glass with pure water represents a pure substance, one of the glasses that did not disperse the light.

Which glass represents a solution?

The other glass that did not disperse the light is a solution.

Pure substances and solutions do not disperese water. Diluted coloids look clear but disperse light.