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this page, Physics - liquids properties, capillarity, optics French
Liquids/ surface tension (a liquid has a surprising cohesion, it gathers itsel)
the foams
-
liquids and dampening
(some matters doesn't like each other ; a liquid makes holes if an enemy is encountered ;
rinsing liquid)
-
liquid flow
(neck of bottle that pisses around, plane wing, the water and the sight ..)
- water and sight-
capillarity (a misterious climbing force)
-
Adhesives
(glues)
- liquids, surface tension : the water drop; the insects which go on water; bubbles, small or giant (of soap for the children or
special for shows); the aluminium coin that floats on water.
For each one of these cases, it is an effect of the surface tension of the liquids. This one comes from the cohesion of
the last molecules of the surface which form like a skin. The water drop is somehow
locked up in a soft and deformable bag ; objects of greater density than the liquid itself can be sustained on this
peal, dressing it a bit as a cup, like the quoted insects depress "the skin" of the water with their legs without
getting it cracked (otherwise they would drown themselves).
- Useful application ;
drying on the sink
; due to the
surface tension of the liquids, glass, pot, or carafe put down will keep around a cord of water making sealing
that will not dry.
Set glasses and dishes turned over on a fabric or a paper which will evaporate the water by capillarity, or tilt them or better lay them horizontally !
Small drops are not going to run down. Let them dry on open air or wipe them.
Overflowed liquid.
A water, milk or oil pool has its edges like contained in an invisible bag.
It is possible to collect the liquid, using a shovel or a spatula, most of the water, milk or oil which has been just reversed.
see Brico,
ennoyances) Liquids can be guided by a simple water pipe posed on a
concreted ground or a tiling: one can thus delimit a zone of cleaning by limiting the flood.
Funny:
the
paper clip, the
pin, the aluminum coin which floats whereas they are denser than water;
there is an easy way to reach bus that point actually they does not float but is posed on “the skin of water”, like the insect. To produce
this turn, it is necessary to choose a very small paper clip, a pin with small head, a coin of currency aluminum (old), or even an end of
thin copper or iron wire well straight. One cuts out a small piece of paper fine (cigarette, toilet paper.) and one flat poses it on water;
one gently poses the pin, trombone etc above, most horizontally possible and one waits until paper runs (or one helps it by gradually
inserting it on the edges using a stick). These objects float, slightly inserted on the skin of the water which becomes deformed around them, out of basin.
The compass, with the pin which floats, you will be astonished by not. to lose north; indeed, it will be directed, head
towards the south, if it is as what I noted.
liquids, dampener, not dampener
liquid of rinsing (dish washing machine).
There are many strange behaviour for the liquids which can thus "love or hate" certain matters (known
as dampening or not dampening): if a body is non dampening, the water, taken as example, runs above by
forming balls. The liquids of rinsing limit the water consumption getting the dishes and glasses non dampening at
the time of the rinsing cycle ; so that water does not stick to them, dislocates and carries the dirtiness separated
beforehand by surface-active component. At the contrary, a dampening surface attracts the water, which adheres and is
spreading out onto to it. It is what one can observe in a glass full of water : water goes up on the edges because
molecules of glass and water attract each other.
If you plunge a tube (cap of pen) in water, you will see very well water being like sucked and so going up a little around the
tube. One obtains even a pretty sucking noise when it is withdrawn.
AGGRAVATING, the midge in the glass : it is this phenomenon which irritates you when you want to catch a
midge in your glass : each time you approach the spoon, water cup up on a little length along the spoon and the
small beast slips on the slope, thus moves away a little and escapes from your bad projects !
The Teflon (*) which coats the frying pan :Teflon makes it non dampening and oil cannot
be spread onto (it forms little patches). Oil needs a certain thickness so that it agree "to cover" the bas of
the pan. In the same way the product "rain XY" for the windshield of the car, which get the glass non dampening so
that the water drops flee to the top at high speed, without flippers (the water drops cannot gather and amalgamate any
more, as they like to do by affinity).
(*) Teflon: this nonadherent matter was difficult to fix on the stoves, where it does not adhere
either ! the ustensils are thus dug micdo-cavities in which Teflon takes taken (clings), from where undoubtedly its
brittleness and its deterioration in small plates.
Soap, detergents,
soluble oil.
They
all are of greasy substances soluble in water, therefore
dampening, whereas they are not by nature. In the capacity
as greasy substance, they can dissolve another greasy
substance (thus to clean) and in the capacity as dampening
product, they can be rinsed with water (oil/grease usually
do not like water and does not mix it with). It is a special
process which got famous the "Marseille soap" in France,
which is to some extent "fat soluble in water". One can thus
clean dirty grease with oil (it is what one can use and not
gasoline), but it is necessary "to be ungreased" afterwards.
The soap makes both things at a time. Olive oil and
Benjamin Franklin ;
curiously and contradictorily, oil and water
which are not "in love" each other get along sometimes with
wonder, without however mixing (honour is preserved); since
Greek antiquity, it is known that the waves calm down if one
pours oil on the sea, process used sometimes by the
fishermen. Benjamin Franklin was interested in the surface
covered by oil and close to London, poured a spoonful of
olive oil in a pond; this spoonful covered approximately 100
square meters, which is considerable. Much later, Rayleigh
deduced from it that the oil film was with its minimum
thickness, that is to say thick as one oil molecule ! One
thus calculated the size of the first matter molecule, that
of the ' olive oil, approximately one millionth of meter
(one thousandth of millimetre, say one micron).
Amusing
; in
connection with dampener, here a question put by a scientist
: when it is raining, are we going to run or walking
normally ? indeed, one hit more water if one runs ! what is
right but. do you have the answer ? so much the better, you
are still wise.
liquids flow, the bottle or the pan which "pisses out" everywhere.
The flow of liquids is not always simple due
to affinities between materials themselves (see dampener/not
dampener ), but also because of the phenomena of internal
and atmospheric pressure. It is the case when one pours wine
which tends to run along the neck of the bottle. Why?
because of the curve of the valuable liquid at the exit of
the neck : the part of the wine close to the glass runs
faster than the external part (to the air) and so its
internal pressure on this side is lower (principle of
Bernouilli); the external atmospheric pressure thus push
liquid against the bottle. Let us retain that it is a
problem of curve of the liquid and difference in pressure
which results from it.
Another
phenomenon of curve, similar for its effects, conditions the
behaviour of a coffee spoon placed in the water jet of a tap
and it is the same for the wing of plane. Hold a spoon by
the end of the handle and push it slowly towards the jet of
the tap, back ahead (convex face), that is to say, the
hollow towards you. Arrived in contact with the jet, it jerk
abruptly ahead, as it is aspired; this phenomenon is used
for the wings of planes which are thick and curved on the
upper side (above). Although supported by the lower side
with the pressure of the air, the main lifting force of the
wing comes from an aspiration by the top ! Make the
experiment of the spoon, you will be astonished. Again, it
is different rates of flow speed which induce different
pressures.
Liquids,
capillary forces ; no, it is not about hair in a liquid but
speaking to the force which makes climb up a liquid in a
very fine tube (known as capillary, therefore fine like a
hair). They does not understand this phenomenon very well
but they nevertheless explain it ! . Well, let's watch at
the effects : the capillarity has practical applications :
to hoe the ground consists in making mounds which break the
capillary conduits of the ground, so that evaporation of
water is reduced. A hoeing is worth two watering because it
retains water.
Watering (vacation)
; if
you want watering your plants while having some vacation
days, you can place large cotton wicks on the ground of
the pot (three to five cm
stripes frorm a floor cloth) with the other side soaking in a basin
full of water. See "garden" in Physics
Sap of the
trees ; the force which push the sap up into a
plant would stem from capillarity but it is not really sure
at all ; some people think that phenomena would be due to
the evaporation, which, creating a vacuum, would suck the
sap. This theory is interesting but I cut down a branch of a
tree at half the lenght and it was dripping days and days despite the products
applied but mainly after having heightened it, pushing the
tip of the remaining branch up and higher than the other part (with a strong stack). Conclusion ? "it" push up and strongly !
Liquids, the water and the sight?
Somebody in the swimming pool, the broken stick).
A bird which plunges trap the fish whereas this last is not where it sees it (he
makes the necessary correction).
The fish which jumps out of water made the same correction to catch the insect! if you look at somebody in the
water up to the neck, you see the part of his immersed body ridiculously deformed: it does not have almost any more a chest
and its legs as its basin are packed and broad. This effect comes from the
luminous rays which are broken (deviated) between the two mediums which are
water and the air (excepted vertical rays); the angle
which the considered ray forms is defined by a "index of
refraction", which depends on the nature of the liquid or gas. While plunging a
stick in water, one sees it "broken" under
the surface. However, it is always right! conclusion,
the end of the stick is not there or it is seen.The photograph here-after shows
very well this phenomenon :
1/ sight over the surface of water :
the caiman appears flattened, with almost horizontal short
legs (I lined up the outline) whereas 2/ : through the vertical pane, one sees legs hanging until the bottom,
enormous because increased by an effect of magnifying glass (what is experienced diving with a mask).
Click to see the caiman behind the vertical pane
of the basin.
Surfusion. The easiest overfusion to observe is that of water: it may not be in the state it should adopt. The second is ice water which can still be liquid at just under zero degrees (and who takes a single shot at the slightest disturbance).
The sea ice, given the salinity, of course, since salt also changes the freezing point, can still be liquid when it should be icy, at almost five degrees less than the theoretical point. Under the effect of a disturbance, it can then freeze abruptly at once.
This phenomenon involves the agitation of the water, the dissolved gases, the impurities around which the first crystals form, etc. You can't explain everything, and especially you can't predict. There have been instances where hot water poured freezes faster than cold water.
"P"
Worrying: the state of over-fusion of winter rain in cold weather.
It is not so uncommon for of rainwater to fall into a state of overfusion (slightly below zero, it should be ice). You're in the car and the rain doesn't make you fear anything. But as soon as it hits the ground, but also your windshield, it instantly turns into ice! So beware,
Evaporation.
A hot liquid evaporates and produces cold by relaxing. But if you pour water into a hot frying pan, two cases occur: if the pan is
medium-hot, the water (it's funny), and gradually disappears.
If the temperature of the pan is sufficient, the water forms small balls that roll and jump
before gradually disappearing. It is a way for a cook to know the temperature of his stove, which then reaches at least 180 degrees,
temperature needed to seize meat.
Flow,
Let's see here the coherence of liquids, that is, their ability to meet and regroup, into a single massive malleable body. Different liquids
poured into a glass separate into layers of affinity and not just density. This property is also shared with
other bodies, including grains that, like liquids, can move. Forces assemble external molecules
of a liquid that contain it in a kind of skin. A liquid does not like to be separated and
groups in scattered droplets if the support does not absorb them, or in puddles, waiting for the opportunity to
merge. Water can remain in fine droplets even vertically (glass), until drying on site.
Etalé, the liquid takes more or less at ease, always to spread, depending on the nature of the medium and the rules of gravity.
! The varnished wooden plank of a bench looked clean when this lady, whom we met afterwards, sat on it. Las, it had rained and she really soaked her butt!
the water that had remained on it, "contained in his skin", was not a thin film but a thick layer that I later chased out of my hand! maybe a little half-inimeter.
A fluid oil like olive oil spreads on water until the last molecule flattened. The iration of oil on the ground comes from the refraction and diffraction of light on its thin layers.
Cohesion of a liquid.Pour, the liquid forms a flow that is held and also gives rise to a vortex phenomenon in the sink's sink (coiling due to the earth's rotation).
Hunted water is body and aspire literally the water of the reserve, even managing to bring it up to follow the flow.
We know the strength waves and the bumper blows they are able to strike; the same is true in pipes where a runoff can,
by the force of inertia, gut the pipes.
The bodies of water reflect on an obstacle and go in another direction. The phenomenon can be observed at the seaside, near
a that returns water and sailors are familiar with the cross-seas, a meeting place for waves that have been pushed or from
different directions, including the island of Sein, meeting the North Sea and the Baltic, near, between groups of islands or shoals, and in many other places.
"P"
The mascaret is another illustration, two masses of water that meet. The river that flows towards the sea, that of the sea that rises with the tide.
In Canada, there is a northern road that is only open to hGVs in the winter; for good reason, since it a river
jelly. But under the ice the water, which is still very lively, suffers the weight of the gear and goes forward and towards the banks as under the effect of the bow of a boat.
This effect becomes very troublesome in the corners, even dangerous because the ripples under the ice collide at the slope of the turn, in his elbow, and return back, causing a agitation of the water
likely to break the ice. Faced with the risk, the drivers, all experienced, are listening to the ice and take the necessary precautions. However, it was considered useful to study the phenomenon, which led to a change in the course of the river's curves in order to
return differently and disperse the underwater wave.
Memory of Water.The memory of pure water is in no way comparable to that of metal alloys that return to a shape formerly given to a
other temperature (good for magic tricks!). This is in fact a highly controvered hypothesis that pure water would retain the properties of bodies that would have
were formerly dissolved, so disappeared. The theory implicitly defends the homeopathic effect whose active elements are so diluted that virtually nothing remains. Its defenders
argue that pure water does not exist and that if there is a memory, it must be searched in the countless particles that were there at the event, which are still there and which could keep track of it. We are at that point, and we hardly talk about it anymore.
Except that a certain Martin Chaplin, London South Bank University, claims that the properties of liquid water are difficult to predict because it contains dissolved substances, that it interacts with the environment, solid or gaseous, and that no
doesn't really know how it's structured. Water, which has such a small and simple molecule, is nevertheless able to satisfy all the needs of life. The structure of its oxygen atom and its two hydrogen atoms, however, is not so obvious that one
believes : in what forms can they associate? he represents it as an example as Mickey's head with a large round and two ears (oxygen atom and two hydrogen) to show that its structure, or layout of its constituent elements can vary,
under the action of other substances, and consist in different volumes (e.g., tetrahedrons).
It is already known that it has water of different densities, including the famous heavy water, which is structured differently, while remaining water.
Beyond that, other researchers assume the presence of water lighter than normal and another heavier than ice. From there to preserve the memory of past compositions, there is not far.
Foams; Research on the bubbles (bubbles kind those of soap) was always very active because they are amusing
us. One seeks to produce them as well as possible, for a better effectiveness of the detergents (detergents,
liquid of cleaning).
A bubble consists of a very thin matter film, whose molecules hold together like an elastic skin (see liquids
tension). With liquids with very strong cohesion (surface tension), one manages to create rather large bubbles so that a person can get
inside without destroying them (spectacle of illusionnists).
The idea of the bubbles walked on there after to the creation of the gas concrete: it was not a question of carrying out more
rank bubble of very fine concrete to enter the Guinness of records, but of making foam a compact material by nature. This light gas
concrete, filled with bubbles of air, is a very effective insulating ; one gains in quantity of product, in weight to
carry then to stand up, by ensuring a good insulation at the same time.
Undoubtedly can one reproach him his friability and his lack of resistance, but associated with a framework, it is very interesting.
Why now not make foam the metal ? this dream is like reality. Let us Imagine all the properties of the light aerated concrete
transposed to the metal, with a great more resistance, what for a stake !! monopiece body of aluminium foam cars,
titanium foam parts, handles of stainless steel foam knives. The final act would be played moulding, as for the lght foamed concrete and
there would not need anymore to work cor weld. One would mould complex structures of only one blow.
;
the force which makes stick (to adhere) the adhesive on another material comes from the attraction of atoms between them, since they are very close to each other (force
of Van der Waals). The phenomenon, not encircled very well, is always the subject of research; the polymers, joining of molecules forming of the giant
molecules, play a dominating role in the manufacture of the adhesives. See also "glue and use".
This Post-it note magnified 225 times can be reused several times because a gooey film of glue is released by a few bubbles containing the glue
when the paper is pressed to a surface. When all the bubbles have been used, it doesn't stick anymore.
Liquids/ surface tension
molecules, play a dominating role in the manufacture of the adhesives. See also "