Encyclopedia of Science

[SweetSammi]

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I have a test on Tuesday and I need to know what these mean Heterogeneous, Colloid, Alloy, Sol, Isotope, Suspension and Chromotography Ya I am alitte embarresed not to know these things but maybe you can help

[SweetSammi]

PLEASE HELP ME OUT

[dsoz]

Homogeneous, same throughout

Heterogeneous, different throughout

[treelover]

hetero means different gen beginning I BELIEVE AS THE GUY BELOW SAYS IS MEANS THAT WHAT IS THERE IS COMPOSED OF DIFFERENT THINGS (oops!!! sorry for the caps!!) Homogenous means 'the same'
or one bit is the same as another.

Theres lots of different usages, but since your word seem to be about materials, I would define heterogenous to mean well mixed.

Colloid - think of it as a collection of things. like things that like each other sticking together.

If you have fine material in water - like dust, any you want to remove it you will have to leave it to settle. This takes a very long time and the slightest disturbance to the water will stir it up again. Straining it out is very difficult, you need a extrememly fine mesh and the mesh would soon clog up.
Add a 'flocculant' and this attracts or glues the dust to it, This forms bigger clumps or 'colloids'. These colloids being larger and more massive than the surrounding fluid, sinks faster and the water clears faster.
A colloid in fluid is heterogenous.

Alloy is a mixture of two metals usually. Like brass of stainless steel.
Usually one metal is added in small amounts to another to change its physical properties. The distribution of the metals in the allow is usually considered to be even, therefore it is homogenous.

Sol and flux are opposites. sol is stable un-moving, flux is mobile and changing a gell is sol and water is flux, one moves the other doesnt.

Isotope - iso means the same. On one scale matter is atoms. Atoms are mixed up electrons neutrons and positrons.
Electrons are negatively electrically charged, positrons are positively electrically charged and neutrons are neutrally charged ( not positive or negative ).
Electrons live far from the centre of the atoms, positrons and neutrons live at the centre.

Positrons attract electrons. The number of positrons at the centre affect how may electrons there are living around the outsides of the atom ( p.s. they dont really 'live' - its just a way of describing the situation )

Electrons weigh next to nothing. Positrons and neurtons weigh the same and both weigh much more than electrons.

If an electron was a fly weight then positrons and neutrons are elephant weight!

The numbers of electrons and neutrons and positrons in an atom, are unique to that type of atom. Types of atoms are called elements.
Elements are like oxygen, copper and carbon.

If an atom had more neutrons than it should, that atom is said to be more massive. Electrically a more massive atom is identical to a normally massed atom and is called the same thing.

Carbons atomic mass is usually 12, but the rare few are more massive e.g. Carbon with an atomicweigh of 14.

Electrically, C12 and C14 are the same thats why they are both called Carbon, these lighter and heavier versions are called 'isotopes'
Usually, the 'heavier' isotopes are radioactive!!

Suspension. Some elements and compounds, in a fluid, dissolve and spread out to form a 'homogenous' (evenly spread) dissolved part of the fluid. This in water is the solute load. Some elements and compounds wont dissolve, or the water has dissolved as mush of it as it can. This if theres enough of it in large lumps (heterogenously distributed) its falls out of the fluid to the bottom and forms the bottom or bed load. Some elements and compounds are small emough to stay in the fluid and the motion of the fluid keeps then in the fluid. Those elelments andcoumpounds are said to be in suspension, that is suspended in the fluid. A fluid with suspended part to it is a suspension. Suspensions are heterogenous. Milk from different kinds of cows have different amounts of suspended fats and protiens in the milk fluid that carries them.
Mixing the milk of different cows forms a averaged out mixture and can be said to be homogenised. Other processes on milks change the character of the milk and this milk is also called homogenised milk

Chromatography. Chroma = colour, graphy= well... a graph!!

So 'colour-graph'. This word is used to name a technique in science based on a method of separating out a mixture of substances over a area.

Think of a graph, it is on a shhet of paper and it has axis, one in one direction, the other in another direction.
Single axis chromatography separates a mixture of substances along one axis. Usually a solvent is poured onto a filter paper with the mixed substance on.
The substances depending on whether they react to the solvent differently, will pass into solution with the solvent more quickly or slowly than thother parts of the mixture. They move with the solvent front its middle or dont move at all.
Chromatograpgy cal tell you what is in a mixture or you can use it as a way is separating parts of a mixture. You Take a homogenous mixture and create a heterogenous areas on the graph of filter paper.

Hope this helps.

BoB

[treelover]

ERRRR sorry NOT positrons PROTONS.

Sorry

BoB

[treelover]

More mistakes!!

Chromatography.
Last line should read Heterogenous to homogenous.

I'm tired!

BoB