217
Bermuda Bubbles
What
the pump
button to
down
to release
airwith
bubbles.
What to
to do:
do: Hold
Use the
fill the
red bottle
compressed air.
What
boatyou
normally
floats
because
it is less
dense
What happens:
happens: The
When
open the
valve,
the water
in the
tankthan
fills water.
with air
The
air
bubbles
mix
with
the
water,
lowering
the
density.
Now
the
boat
is denser
bubbles and the boat sinks.
than the water beneath it and so it sinks.
HOW IT WORKS
1. Things float when they are lighter (less dense) than the fluid that
surrounds them. A wooden boat floats even if it is
full of water, because wood is less dense than water
(Not true of a few very dense woods).
wood
A ship made of steel is less dense than
water because it is hollow. Its average
density is much less than water so it floats
with most of its hull out of water.
steel ship
water inside and
it still floats!
air
2. If, however, the water is full of air bubbles, it is a much lighter
(less dense) fluid than ordinary water, so may not be dense enough
to support the ship.
Water full of
bubbles can’t
hold the ship up
USA
solid
(growin
Bermuda
Florida
Costa Rica
South
America
3. The name of the exhibit comes from the “Bermuda Triangle”, an area
of the Atlantic between Bermuda, Florida and Costa Rica, where
ships have disappeared in mysterious circumstances. It has been
suggested that sudden eruptions of carbon dioxide gas from the sea
bed may be responsible!
d
ng)
4. In this region, as in many places around the world, there are large
4. Salt-bearing strata in the sea bed in that region are periodically
deposits of methane gas. When submarine landslides or slight
exposedinbytemperature
underwateroccur,
landslips,
set of
offmethane
by earthescape
movements
increases
“burps”
from and
the
sea
bed
erosion.
These
slats
dissolve
quickly
in
the
sea
water
and
reserves in the seabed. These gas bubbles decrease the density of
produce
lot of gas,
the same
way as an Alka-Seltzer
the
water, a
causing
shipsinonmuch
the surface
to sink.
However,
in awhen
recent
survey by in
Lloyds
of London, no evidence was
tablet does
it dissolves
water.
found to indicate that there were significantly more shipping losses
in this area.
salt
salt
salt
.
DID YOU KNOW?
• Ships float at different depths in different “sorts” of water. If the
water is warm, it is less dense, so the ship floats lower in the water.
If the water is salty, it is more dense, so the ship floats
higher in the water. The “Plimsoll Line” on the side of
ships shows the legal holding limit of the ship in
various oceans (e.g. Winter, Salt Water). Samuel Plimsoll
was the M.P. for Derby in the 1860s who
campaigned against the dangerous overloading of
merchant ships.
Compressed air in
air out
dive
water in
water out
rise
• Fish are like submarines (or vise versa). They
have a bladder of air inside their body which
they can adjust to permit them to float under
water. Sharks are different - they have no
swim bladder and have to swim all the time
to avoid sinking to the bottom!
TF - Tropical Fresh Water S - Summer, Salt Water
F - Fresh Water
W - Winter, Salt Water
T - Tropical Salt Water
• Submarines float submerged, which means that
their average density has to be the same as the
water that surrounds them. They have tanks
inside the hull which can either contain water or
air, so the average density of the submarine can
be adjusted to “hover”, dive or come to the
surface in any sort of water.
A submarine is even more susceptible to sinking
in bubble-filled water than a surface ship
because of the fine balance required to keep it
hovering under water.
sharks have to swim
all the time!
THINGS YOU CAN TRY YOURSELF.
• When you are swimming, if you breathe out fully, you will feel yourself sinking.
Make sure it is air you then breathe in, otherwise you will sink even faster!
bony fish float
WANT TO KNOW MORE?
swim bladder
STUART STREET
CARDIFF
CF10 5BW
See the Hot Air Balloon exhibit. The balloon will float up through the
atmosphere, like a submarine rising through the sea, provided the air inside it is good
and hot.
T 029 20 475 475
F 029 20 482 517
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