Physical Properties of Water Video Lecture - Chemistry Class 11 - NEET

water it's all around us makes up 70% of
the Earth's surface and about 60% of
your body let's start with the basics
water is a colorless and transparent
substance when it is pure it has no
smell and no taste if you've ever
thought that one type of tap water
tastes different to another you're not
wrong
tap water in different areas may have
slight impurities from various metal
ions water is a liquid at room
temperature it freezes at 0 degrees and
boils at 100 degrees at standard
pressure but have you ever wondered why
the boiling point of water is higher
than for example methanol well you might
know from this video that water is a
polar molecule with slightly positively
charged hydrogen and slightly negative
oxygens imagine a bunch of water
molecules in a beaker they are in liquid
form so can move around each other but
the Delta positive hydrogen's from one
molecule are weakly attracted to the
Delta negative oxygen of another this is
a type of intermolecular force and it
has a special name hydrogen bonding
because of this the water molecules need
quite a bit of energy to overcome the
hydrogen bonds and escape from the
beaker as a gas water is a very good
polar solvent so good it's often called
the universal solvent that's a bit of an
exaggeration but it's certainly true
that many common chemical compounds will
dissolve in water
here's just a few hydrochloric acid and
many other acids sodium hydroxide along
with other bases soluble salts such as
table salt sodium chloride
and sugars here's a challenge though can
you think of a large and important type
of compound that won't dissolve in water
and instead floats on its surface more
importantly can you think why they do
this pause the video think carefully and
resume when you've got the answer well
the answer is lipids or in plain English
oils or fats they don't dissolve in
water because they're nonpolar and
therefore hydrophobic meaning they don't
like mixing with water one of the most
unusual qualities of water is that it
can act as either an acid or a base a
water molecule can either accept a
proton and become a hydronium ion with a
+1 charge or donate a proton and become
a hydroxide ion with a minus 1 charge
this is one of the reasons why water is
so useful in all sorts of organic
chemistry reactions we already use water
third bathing laundry many industrial
processes and of course drinking but
perhaps even bigger things lie ahead
you see many scientists all over the
world are working on developing hydrogen
as an alternative fuel source we know it
works for this purpose but there are
problems with storage transportation and
refuelling that are holding us back
nonetheless a lot of people believe that
in the not-too-distant future many of
our machines and industries will be
powered not by hydrocarbons for hydrogen
gas and where are we going to find an
almost limitless potential source of
hydrogen to use for these purposes you
guessed it the humble water molecule
you