Physical Science 8R

Notes 6-1


What is a Suspension?


A suspension is a mixture of two or more materials that separate upon standing.

· Ex. Soil and water

· Suspensions settle in to layers with the heaviest particles at the bottom since they settle out first.


The particles are very small in a suspension, but they are larger than the particles of a solution.


Properties of solution compared to suspensions.








Particles are evenly mixed

Particles settles out on standing

Particles are too small to be seen

Particles can be seen


Common suspensions are:

A)       Salad Dressing

B)       Dust and air

C)     Smoke

D)     Clouds


Physical Science 8R

Notes 6-2


How can a suspension be separated?


Particles in a suspension will settle upon standing.

-       The smaller the particles the slower the settling.


Filtration is the removal of particles of a suspension by passing the suspension through a filter.

-       Filters have pores that are big enough to let some of the mixture through, but too small to let everything.


Coagulation is when chemicals are added to a suspension to cause the particles to clump or stick together.

-       Clumps settle out more quickly.

-       Alum causes blood to clot or coagulate.


Spinning or centrifuging is spinning the suspension at high speeds.

-       The particles are forced to the bottom of container.

-       Red blood cells can be centrifuged from suspension.


Physical Science 8R

Notes 6-3


What is an emulsion?


When one solution is suspended in another the result is an emulsion.

-       Oil and water

-       Milk

-       Temporary emulsions will settle out.


Permanent Emulsions do not separate upon standing.

-       The particles are smaller than a temporary emulsion.

-       Homogenization is the formation of permanent emulsion. Such as in milk.

-       Particles are broken into very small particles to stay in suspension.


Many detergents are emulsifying agents.

-       An emulsifying agent keeps a emulsion from separating.

-       Soap allows oils to dissolve in water.

-       Gelatin and egg yolk can make emulsifying agents.


Physical Science 8R

Notes 6-4


What is a colloid?


A colloid is a suspension in which the particles are permanently suspended.

    - They can be of different phases of matter.

    - Glass, Paint, Smoke

- Homogenized milk, Fog, Sea foam


Particles in a colloid are not as small as a solution, but they are smaller than the particles of an ordinary suspension.

-       Filtration doesn’t work since the particles are so small.

-       The particles are smaller than the pores of the filter.


When light hits the particles of a colloid they tend to spread out.

-       This is called the Tyndall effect.

-       That is why a colloid appears cloudy like headlights through fog.


Physical Science 8R

Notes 6-5

What are air and water pollution?


Pollution is the adding of harmful substances, called pollutants, to the environment.

-       They can be solid, liquid, or gas.


Most pollution is caused by humans.

-       Car and truck exhaust is a huge contributor to air pollution.

-       Factory wastes pollute air, water, and soil.

-       Burning fossil fuels such as coal and oil release pollution into the atmosphere.


There are many sources of water pollution:

-       Farm pesticide runoff

-       Sewage

-       Hot water from nuclear power plants


Water that is safe to drink is called potable.

-       Water can be made potable by going through a series of steps to purify it.

-       Chlorine is added to kill bacteria.

-       Settling and filtration are also involved.


Air pollution can cause breathing problems and respiratory illness.

    Ways to cut down on Air Pollution:

A)       ride a bike

B)       walk

C)     Car pool

D)     Turn down home thermostat

E)       Drive more efficient cars