Alex via Neatorama
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Water, good ol' H2O, seems like a pretty simple substance
to you and me. But in reality, water - the foundation of life and most
common of liquid - is really weird and scientists actually don't completely
understand how water works.
Here are 5 really weird things about water:
1. Hot Water Freezes Faster Than Cold Water
Take two pails of water; fill one with hot water and the other one with
cold water, and put them in the freezer. The hot one would be frozen before
the cold one. But wait, you say, that's counterintuitive: wouldn't the
hot water have to cool down to the temperature of the cold water before
proceeding to freezing temperature, whereas the cold one has "less
to go" before freezing?
In 1963, a Tanzanian high-school student named Erasto B. Mpemba was freezing
hot ice cream mix in a cooking class when he noticed that a hot mix actually
froze faster than a cold mix. When he asked his teacher about this phenomenon,
his teacher ridiculed him by saying "All I can say is that is Mpemba's
physics and not universal physics."
Thankfully, Mpemba didn't back down - he convinced a physics professor
to conduct an experiment which eventually confirmed his observations:
in certain conditions, hot water indeed freezes before cold water*.
Actually, Mpemba was in good company. The phenomenon of hot water freezing
first, now called the "Mpemba effect" was noted by none other
than Aristotle,
Francis Bacon and René Descartes.
But how do scientists explain this strange phenomenon? It turns out that
no one really knows but there are several
possible explanations, including differences in supercooling (see
below), evaporation, frost formation, convention, and effects of dissolved
gasses between the hot and cold water.
*In reality - of course - it's much more complex than that: hot water
freezes first (it forms ice at a higher temperature than cold water),
whereas cold water freezes faster (it takes less time to reach the supercooled
state from which it forms ice) - see discussion on our previous
blog post about this topic.
2. Supercooling and "Instant" Ice
Everybody knows that when you cool water to 0 °C (32 °F) it forms
ice ... except that in some cases it doesn't! You can actually chill very
pure water past its freezing point (at standard pressure, no cheating!)
without it ever becoming solid.
Scientist know a lot about supercooling: it turns out that ice crystals
need nucleation points to start forming. These nucleation points could
be anything from gas bubbles to impurities to the rough surface of the
container. Without these things, water would continue to be a "supercooled"
liquid well below its freezing point.
When nucleation is triggered, then a supercooled water would "instantly"
turn into ice, as this very
cool video clip by Phil Medina of MrSciGuy
shows:
Note: Similarly, superheated water remains liquid even when heated past
its boiling point.
3. Glassy Water
Quick:
how many phases of water are there? If you answer three (liquid, gas,
and solid) you'd be wrong. There are at least 5 different phases of liquid
water and 14 different phases (that scientists have found so far) of ice.
Remember the supercooling we talked about before? Well, it turns out
that no matter what you do, at -38 °C even the purest supercooled
water spontaneously turns into ice (with a little audible "bang"
no less). But what happens if you continue to lower the temperature? Well,
at -120 °C something strange starts to happen: the water becomes ultraviscous,
or thick like molasses. And below -135 °C, it becomes "glassy
water," a solid with no crystal structure. (Source)
4. Quantum Properties of Water
At a molecular level, water is even weirder. In 1995, a neutron scattering
experiment got a weird result: physicists found that when neutrons were
aimed at water molecules, they "saw" 25% fewer hydrogen protons
than expected.
Long story short, at the level of attoseconds (10-18 seconds)
there is a weird quantum effect going on and the chemical formula for
water isn't H2O. It's actually H1.5O! (Source)
5. Does Water Have Memory?
In
the alternative medicine of homeopathy, a dilute solution of a compound
can have healing effects, even if the dilution factor is so large that
statistically there isn't a single molecule of anything in it except for
water. Homeopathy proponents explain this paradox with a concept called
"water memory" where water molecules "remember" what
particles were once dissolved in it.
This made no sense to Madeleine Ennis, a pharmacologist and professor
at Queen's University in Belfast, Northern Ireland. Ennis, who also happened
to be a vocal critic of homeopathy, devised an experiment to disprove
"water memory" once and for all - but discovered that her result
is the exact opposite!
In her most recent paper, Ennis describes how her team looked
at the effects of ultra-dilute solutions of histamine on human white
blood cells involved in inflammation. These "basophils" release
histamine when the cells are under attack. Once released, the histamine
stops them releasing any more. The study, replicated in four different
labs, found that homeopathic solutions - so dilute that they probably
didn’t contain a single histamine molecule - worked just like
histamine. Ennis might not be happy with the homeopaths’ claims,
but she admits that an effect cannot be ruled out.
So how could it happen? Homeopaths prepare their remedies by dissolving
things like charcoal, deadly nightshade or spider venom in ethanol,
and then diluting this "mother tincture" in water again and
again. No matter what the level of dilution, homeopaths claim, the original
remedy leaves some kind of imprint on the water molecules. Thus, however
dilute the solution becomes, it is still imbued with the properties
of the remedy.
You can understand why Ennis remains skeptical. And it remains
true that no homeopathic remedy has ever been shown to work in a large
randomised placebo-controlled clinical trial. But the Belfast study
(Inflammation Research, vol 53, p 181) suggests that something is going
on. "We are," Ennis says in her paper, "unable to explain
our findings and are reporting them to encourage others to investigate
this phenomenon." If the results turn out to be real, she says,
the implications are profound: we may have to rewrite physics and chemistry.
(Source)
So far, other scientists failed to reproduce Ennis' experimental findings
(throughout, Ennis herself was skeptical of the result's interpretation
that water has a "memory" but maintained that the phenomenon
she saw was real).
See also Jacques
Benveniste's Nature controversy | Louise
Rey's thermoluminescence study
More recently, a team of scientists at the University of Toronto, Canada,
and Max Born Institute in Germany, studying
water dynamics using fancy multi-dimensional nonlinear infrared spectroscopy
did find that water have a memory of sorts - in form of hydrogen
bond network amongst water molecules. Problem for homeopathy was, this
effect lasted only 50 femtoseconds (5 x 10-14 seconds)!
Bonus: Ice Spikes
photo: SnowCrystals
Ice spikes are, well, spikes that grow out of ice cube trays. They look
like stalagmites found in caves, and you can make 'em yourself using distilled
water. Kenneth G. Libbrecht of SnowCrystals
explains:
How do Ice Spikes Form?
Ice spikes grow as the water in an ice cube tray turns to ice.
The water first freezes on the top surface, around the edges of what
will become the ice cube. The ice slowly freezes in from the edges,
until just a small hole is left unfrozen in the surface. At the same
time, while the surface is freezing, more ice starts to form around
the sides of the cube.
Since ice expands as it freezes, the ice freezing below the surface
starts to push water up through the hole in the surface ice (see diagram).
If the conditions are just right, then water will be forced out of the
hole in the ice and it will freeze into an ice spike, a bit like lava
pouring out of a hole in the ground to makes a volcano. But water does
not flow down the sides of a thin spike, so in that way it is different
from a volcano. Rather, the water freezes around the rim of the tube,
and thus adds to its length. The spike can continue growing taller until
all the water freezes, cutting off the supply, or until the tube freezes
shut. The tallest spike we've seen growing in an ordinary ice cube tray
was 56mm (2.2in) long. (Source)
Bonus 2: Make Instant Snow with Boiling Water
What do you get when you throw boiling water to the air in subzero weather?
Instant snow. Interestingly, it only works with boiling hot water:
[YouTube clip]
These aren't the only things weird about water. We didn't talk about
how water density changes with temperature (ice, for instance, is less
dense than water so it floats - a key property of water that made life
possible in the oceans and lakes). Nor did we talk about the weirdly strong
surface tension of water, ordered clustering of liquid water, and so on.
If you are interested, check out the Anomalous
Properties of Water article by Martin Chaplin
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