Page 46 - How It Works - Book of Amazing Answers To Curious Questions, 12

AMAZIG ANSWERS TO CURIOUS QUESTIONS -------------------

At what
temperature

is water at its

densest?

D ensity is a measure of how much mass
a material has in a specific volume of
space. Therefore the more atoms per unit
volume a material has and the more mass
those atoms have, the higher the density will How are ball bearings made?
be. When you heat something up, it takes up
more space and therefore becomes less T here are few different parts that make into another machine which rolls the ball
dense. Most materials will be at their densest up a ball bearing, including races, a around between two rill plates. Rill plates are
when they are a solid, ie when their atoms cage, and then the covering to protect the two hard plates of steel which wear away the
are closest together. Water does not follow bearing. The first stage in the process is a flash and smooths the surface of the ball. The
this rule as we all know that ice floats on cold or hot forming operation; a thick piece of ball is then heated to harden it after which it
water therefore ice is less dense than water! wire is fed into a machine where it is cut undergoes a grinding process similar to that
So when is water at its densest? Well, it down by slicing sections off each side. of the rill plates until it is ground down to its
turns out this happens to be around 4°C. This The machine then slams two hemisphere final, very accurate measurements which
is when the water molecules are closest cavities (a bit like a mould) into the piece of often require tolerances as small as a
together. Cooling water further than 4°C wire to make a ball shape. As a result of this millionth of an inch.
causes the density to decrease up to the process, the ball will have a ring of excess The last process is called lapping, which
point where it becomes a solid which is less metal around it, called a flash, which needs requires a similar machine that exerts less
dense than the liquid. This happens due to to be removed. The ball also needs further pressure combined with a polishing paste to
the unusual way that the water molecules polishing to make it perfectly round and give the balls their perfect shiny finish
arrange themselves when turning into a smooth. The ball with the flash is then fed without further reducing their size.
solid, it is known as a crystalline structure
and it is such an arrangement that the It is ground down to its final, very accurate
molecules are further apart from each other
as a solid than when they were a liquid. measurements which often require tolerances
�-&6'
as small as a millionth of an inch

How does How much

de-icer work? electricity does the

D e-icers work by lowering the freezing brain produce?
point of water causing it to turn back
from ice into liquid water. Usually this is due T he brain requires a relatively low power
to the addition of a chemical compound such to operate - around 20 watts, which
as sodium chloride (often called rock salt) or would be enough to power a weak light bulb.
calcium chloride. Most de-icers aren't 20 watts corresponds to 20 joules of energy
designed to melt every piece of ice they come per second. The generation of electricity in
into contact with - they break the bond the brain results from the movement of ions
between the ice and the surface allowing for (charged atoms) through the brain, as
easier manual removal of the ice. opposed to electrons moving through a wire.

46 How It TtOrks WorldMags.net
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