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Name: Vicky J.
Status: educator
Age: 30s
Location: N/A
Country: N/A
Date: 10/27/2003

What is smoke -- solid or gas?


Smoke is particulate material suspended in a gas (air). The particulates may be very finely divided solids or aerosol particles composed of liquid materials.

ProfHoff 740

Hi Vicky!

Smoke is neither solid or gas, it is a colloidal dispersion that is a different arrangement of matter. The colloidal state/the colloids is a kind of matter defined by the size of particles involved, something between a real solution and a suspension, as solutions: 0.1-1.0 nm colloids: 1-100 nm suspension: > 100 nm ( 1 nm (nanometer)= 10 to the -9 of the m) The colloidal dispersions have other physical properties different from solutions and from suspensions. Their particles cannot be filtered by filter paper and also they cannot settle on standing. The colloids can be of several types depending upon the particle phase and the medium phase. The medium phase for smoke is usually the air (gas) and the particle phase are solid like dust or other polluters.

And thanks for asking NEWTON!

(Dr. Mabel Rodrigues)

Smoke is a suspension of solid and/or liquid particles in air. If the particle diameter is less than about 0.1 micrometers (100 nanometers), the particles are so fine that they behave like gases. The force due to gravity is not large enough to allow the particles settle, and their surface charge causes them to repel one another so that the microscopic particles cannot coagulate into larger particles. In addition, collisions with high speed molecules of atmospheric gases (Brownian motion, explained by Albert Einstein) keeps them "bouncing around". Of course wind also contributes to this mixing.

The special danger of nanometer dust particles is that they are "respirable", that is, if inhaled the particles settle out deep in the lungs and remain there. Larger particles slowly are "coughed up". These nanometer particles are especially dangerous if they are radioactive, as in the case of smoke from the detonation of so-called depleted uranium munitions (That is a whole topic itself that you can search on the Internet if you are interested.), or are certain crystal types of silica or asbestos.

Further, nanometer sized particles can pass through cell walls. To put things on scale a red blood cell, the smallest cell in the body is about 700 nm. So nanometer particles can be diffused throughout the body, carried along with body fluids across cell walls. So what characterizes "smoke" is not so much whether the particles are solids or liquids, but rather it is the particle size that dominates its behavior.

Vince Calder


Smoke is a colloid-a mixture in which the dispersed particles have at least one dimension in the range of 1 to 1000 nanometers (nm). The colloidal system smoke has solid particles (dispersed phase) in a gaseous medium (dispersing medium). A typical example of this type of colloid would be dust and particulates in smog. I hope that this answers your question.


Bob Trach

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