Kind: captions
Language: en
[Applause]
have you ever made ice cubes and then
found that when you take them out of the
freezer there are spikes on them this
phenomenon has caused a lot of curiosity
and some concern the truth is there's a
simple physical process responsible for
Ice Cube spikes ice cubes cool first
from their top surface where they're in
direct contact with the cold freezer air
and from which evaporative cooling can
occur so the first ice crystals form on
the surface of the Ice Cube and along
its edges
now as that ice freezes it expands by
roughly 8% that is due to hydrogen
bonding between the water molecules
which makes them on average slightly
further apart than they are in water so
as the ice grows in from all sides the
water in the middle has nowhere to go
and it is forced up and out through a
hole in the ice these holes are often
triangular in shape because ice crystals
tend to meet at 60° angles as the water
comes up through the hole it freezes
around the edges is forming a hollow
Spike and as the ice continues to grow
more water is forced up the spike making
it longer this continues until all of
the water has frozen or until the end of
the spike freezes shut if you want to
make ice cube spikes they can be created
in most ordinary freezers and there are
three steps you can take to increase
your chances number one the ideal
temperature seems to be not too cold
between -5 and - 8 C that's cold enough
to freeze the water but not so quickly
as to freeze off off the tip of that ice
cube Spike number two distilled water
seems to work better than tap water
because even small concentrations of
salt prevent Spike formation number
three a fan in the freezer seems to help
Spike formation by increasing the
circulation of the air and increasing
evaporative cooling and given just the
right conditions very large ice spikes
can form for example on bird baths in
these cases the spikes are known as ice
bases for obvious reasons when looking
at these structures it's interesting to
contemplate that they only form because
of water's unique property of expanding
when it freezes if water didn't expand
when it froze the whole Earth would be
dramatically different because well
since ice is less dense it forms on the
surface and actually insulates the water
underneath so it remains liquid and
allows life to survive in it but if
instead ice were denser than water it
would sink to the bottom allowing for
further cooling of that water and more
ice formation and the ice would build up
from the bottom upwards giving less and
less water for organisms to live in
until if cold conditions persisted for
long enough all bodies of water would
completely solidify as ice meaning that
virtually no life could live in them and
at that point the Earth would also be
completely white so it would reflect
more of the Sun's light into space
leading to further cooling so if water
didn't expand when it froze the whole
Earth would be a cold lifeless
snowball but it all depends on your
starting conditions because if there
wasn't very much ice on the earth to
begin with it would all sink to the
bottom of bodies of water including
Arctic sea ice and that means the
Earth's surface would be less reflective
so it would absorb more heat from the
sun and it would get a lot
warmer so if ice didn't float if ice was
denser than water either the Earth would
be much colder than it is now or much
hotter than it is now and in either case
life on Earth might not exist but if it
did we wouldn't be able to make ice cube
spikes
very of
[Music]
Truth