Sciencemadness Discussion Board

mixtures and properties

toxin - 4-9-2005 at 13:43

Are alloys mixtures or compunds, is mixing together molten copper and iron considered a compund or a mixture(homogeneous or heterogeneus), why ?

Do mixtures maintain the chemical properties of the separate molecules that they are composed of or are there cases in which they don't ?

What is vinigar made out of, is it a mixture ?

Are the properties such as hardness and softness considered chemical or physicial properties, why ?

[Edited on 4-9-2005 by toxin]

12AX7 - 4-9-2005 at 18:00

A subject of much debate between people who think they know things. :D

Quote:
Originally posted by toxin
Are alloys mixtures or compunds, is mixing together molten copper and iron considered a compund or a mixture(homogeneous or heterogeneus), why ?


I would call it a mixture, since the iron solidifies first, at room temperature, the two are present as seperate phases of copper and ferrite (alpha iron). Nickel and copper, gold and silver, nickel and iron (as gamma phase so within some temp limits), etc. form solid solutions so in as much as crystalline metallic lattices are compounds, they do form compounds.

Quote:

Do mixtures maintain the chemical properties of the separate molecules that they are composed of or are there cases in which they don't ?


Hum, dunno. Far as I know, solid solutions range smoothly from one to the other (as you'd expect; they have to be since the ions have to be similar in the first place), while mixtures have the chemistry of both, for example alka-seltzer is what, baking soda and citric acid pressed together? If you could test it without them reacting, you'd observe citric acid and sodium bicarbonate seperately.

Quote:

What is vinigar made out of, is it a mixture ?


Solution, liquid solution. Acetic acid and water are miscible in all proportions.

Quote:
Are the properties such as hardness and softness considered chemical or physicial properties, why ?


Physical. It has little to do with the specific chemistry. Obviously it has to do with bonding and whatnot but, carbon is carbon and diamonds and graphite are quite different!

Tim