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.

 

Solution

Suspension

Mixture

Mixture

Clear

Cloudy

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