Vacuum

A vacuum is a place where there is no matter, not even air. Sound cannot move in a vacuum. No place has a perfect vacuum, because a small number of particles remain, even in outer space. 

A space where only some of the air is removed is called a "partial vacuum". The space then has lower pressure, even if most of the air remains.

 Common uses 
A vacuum cleaner works by pumping away some of the air. The air and dirt in a room rush into the vacuum left behind, where the dirt is caught by a filter.
An automobile engine that burns fuel uses a vacuum to pull in air, which contains oxygen that allows the fuel to burn.
An incandescent lightbulb has a vacuum inside so the hot filament doesn't burn up.

 Industrial uses 

Vacuum is needed for some kinds of machines used for industrial production.  Vacuum pumps are used to pump air out of a vacuum chamber.  It is not possible to create 100% vacuum, but some vacuum pumps are able to create 99.9999% vacuum.  This is called "hard vacuum".  Most industrial purposes do not need hard vacuum.  

Industrial vacuums are mainly used in:
 Food industry
 Electronics industry
 Packaging
 Manipulation
 Coating and degasing

 Scientific experiments 
Vacuum chambers are also used in many scientific experiments in laboratories.  Some experiments in physics and chemistry need hard vacuum to keep any air or other gases from interfering with delicate surfaces or chemicals that can react.

Related pages
Vacuum cleaner

 External links 

 Vacuum (partial) -Citizendium

Category:Matter
Category:Physical phenomena