SUSPENSIONS & COLLOIDS(UNIT TWO, LESSON 2.5)BY MARGIELENE D. JUDAN

LESSON OUTLINE

SuspensionsColloidsProperties of ColloidsSummary: Solution, Suspension, Colloid

3 TYPES OF MIXTURES

SolutionsSuspensionsColloids

SUSPENSIONS

cloudy and heterogeneous. Solute doesn’t dissolve and settle at the bottom

Large particles (can be filtered)

THE SOLUTE DOESN’T DISSOLVE. IF YOU LEAVE THE MIXTURE FOR A TIME, THE SAND PARTICLES WILL SETTLE AT THE BOTTOM.

COLLOIDS

Between a solution and a suspension

Molecules are bigger than in a solution but smaller than in a suspension

Components doesn’t separate out

COLLOIDS VS. SOLUTIONS

Both solutions and colloids have a homogeneous appearance.

But colloids can be determined by its light-scattering effect.

COLLOIDS VS. SOLUTIONS

Solution Colloid Light-scattering

COLLOIDS VS. SOLUTIONS

Solutions cannot scatter light because the particles are too small.

Light-scattering is known as “Tyndall effect”.

COLLOIDS

Colloids are not only for liquid mixtures. The medium could be solid, liquid or gas, and the dispersed substance can also be solid, liquid or gas.

Solution (left); Colloid (right); Notice their difference when light passes through.

PROPERTIES OF COLLOIDS

Tyndall effectBrownian movementAdsorption

1. TYNDALL EFFECT

Known as “light scattering”

Discovered by an Irish, John Tyndall

Tyndall effect in the sky; it happens when large particles are dispersed in the air.

Tyndall effect in the morning.

2. BROWNIAN MOVEMENT

Continuous, random motion of colloidal particles

Particles collideDiscovered by an English botanist, Robert Brown

Continuous, random motion of colloidal particles (notice the blue lines)

Q.) If the molecules are larger than of a solution, why do molecules don’t settle down like suspension?

A.) Electric charges on the particles repel each other and prevent them from combining to larger particles. But heating destroys a colloid because it destroys the electrostatic charges, making them settle down the bottom.

3. ADSORPTION

The binding of molecules to a surface

It is different from absorption.

(ex. Activated carbon – binds molecules to purify)

SUMMARY: SOLUTION, SUSPENSION, COLLOID

ASSIGNMENT: BRING A PERIODIC TABLE ON OUR NEXT MEETING.

ANSWER THIS IN A WHOLE SHEET OF PAPER.

How are colloids important to us? Cite some of its importance. How does it help or benefit you in daily life? (refer to p. 62 for some details) Minimum of two paragraphs (10 pts)

SOURCES:

Science Links 7 http://www.edinformatics.com/

math_science/solutions_suspensions_colloids.htm