February 14, 2019 Thursday
Bedtime Story
Why Mixtures are a Single-Phase Substance
I am sure you are aware that magnets have
polarity (this I think even the least initiated are aware of perhaps because of
the popularity of the concept of a compass and the use of magnet in it).
Just as an aside, compass is one of the
Four Great Inventions of ancient China the other three being the papermaking,
printing and the gunpowder.
In the case of molecular polarity
concerning solvents it means that the polar solvents have molecular dipoles.
Molecules that have dipoles or dipolar molecules
are those molecules that have greater electron concentration on one side of
their molecule than the other.
Because of this difference in density even
in such tiny molecules the part with greater electron density will experience a
partial negative charge as will the other end experience a partial positive
charge.
If such molecular diploes of solvent come
across ions of solute that are either ions or also exhibit electrostatic
bipolarity then they will arrange and orient themselves automatically around
the solute molecules such that they form a solvation shell around each molecule
of solute.
This also means that the solvent molecules
that are in the immediate vicinity of such solute molecules will exhibit a
different kind of arrangement than those present in the other localities of
solvent.
In contrast to mixture colloids do not
exist in such a uniform state and very unique and different mechanisms come
into play in colloids.
One such mechanism that is found in colloids
is that of excluded volume.
An “excluded volume” of a molecule is
defined as the volume of that molecule that is inaccessible to other molecules
in the system.
This mechanism ensures that there is no
overlap between two hard particles thereby maintaining two separate phases.
There are of course other “traditional forces”
that come into play in colloidal systems as well such as electrostatic interaction,
van der Walls forces and others each contributing in their own ways into making
colloidal systems a unique one.
We cannot go into the detailed chemistry of
it as we are only interested in the narration of our story and not keen in
pursuing a bachelor’s degree program.
I have the luxury to do and say so since I
have gathered a sufficient number of formal degrees - some of them admittedly elusive
and which surprises me even today on seeing them lining the walls of my shop -
in my life journey and perhaps they are the only objects of significance that I
have achieved in my life.
Thus blood is a colloid and not a suspension
nor a mixture.
So in case of blood being a colloid the
erythrocytes would not normally sediment primarily because of the existing zeta
potential and secondly because of the continuous pumping of the heart.
Stay tuned to the voice of an
average story storytelling chimpanzee or login at http://panarrans.blogspot.com
Good night Mon Ami and my fellow cousin ape.
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Another great educator and a teacher that I am aware of is
Professor Subhashish Chattopadhyay in Bangalore, India.
While I narrate stories, Professor Subhashish an electronic
engineer and a former professor at BARC, does and teaches real mathematics and
physics.
He started the participation of Indian students at the
International Physics Olympiad.
Do visit him here:
All his books can be downloaded for free through this link:
For edutainment and English education of your children, I
recommend this large collection of Halloween Songs for Kids:
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