What is Colloid?
[[Image:Vintage cranberry glass.jpg|thumb|right|Vintage cranberry glass bowl]] [[Image:WaterAndFlourSuspensionLiquid.jpg|thumb|Not milk, but [[flour]] suspended in water]] A '''colloid''' is a [[mixture]] of one substance spread out evenly inside another substance. They can be in two different [[phase]]s or [[states of matter]]. One substance is the '''dispersion medium''', such as [[water]] or [[gas]]. The other is the [[Dispersed media|dispersed medium]], sometimes called the 'internal phase'. This is usually tiny [[solid]] [[particle]]s. Otherwise, if the dispersion medium is a gas, then the internal phase can be either tiny particles or tiny droplets of a [[liquid]]. Definition: A '''colloid''' is a substance microscopically [[Dispersion_(chemistry)|dispersed]] evenly throughout another substance.<ref>{{Cite web |publisher = Britannica Online Encyclopedia|url = http://www.britannica.com/EBchecked/topic/125898/colloid |title=Colloid|access-date = 2009-08-31}}</ref> The dispersed-phase particles have a [[diameter]] between about 5 and 200 [[nanometre|nanometers]].<ref>{{cite book|last=Levine|first=Ira N.|title=Physical Chemistry|edition=5th|publisher=McGraw-Hill|location=Boston|year=2001|isbn=0-07-231808-2}}, p. 955</ref> Examples: #[[Milk]] is an [[emulsion]], which is a colloid in which both parties are liquids. #[[Shaving cream]] and [[whipped cream]] are colloids of gas inside a liquid. #[[Gel]]s, such as [[agar]], [[jelly]] or even [[opal]]s, are colloids of liquids inside solids. #[[Styrofoam]] and [[pumice]] are gases inside solids. #The red colour of [[cranberry glass]] is caused by the reflection of light off [[gold]] particles in the glass. The glass is a colloid of solid particles inside the solid glass. #[[Mud]] is usually considered a suspension because the dirt will settle, but it may be a partial colloid, particularly with very fine-grained [[clay]].<ref>With a natural substance, it may be only partly colloidal.</ref> #[[Fog]] is a complex mixture in which [[air]] has both water droplets a