Sport & Water –
The Chemistry of Solutions
Sport & Water (swimming)
Activity on and in water dates back as long as human beings have
existed. Water, used for recreational activities, can be traced back over
many centuries with reports showing the Romans and Ancient Greeks
enjoying swimming, although not as an organised sport.
In 1837 the National Swimming Society of Great Britain was formed and
Started to hold competitions as we may recognise them today.
Swimming has been a part of The Olympic Games since 1896, although
between the 1908 and the 1996 Olympic Games, all swimming events
have taken place in the pool rather than in open water (open water
swimming was reintroduced into the Olympic Games in Beijing 2008,
although it had also featured as part of the triathlon events in 2000 and
2004.)
Other water sports and activities
In today’s world it is not just the sport of swimming which takes place
on or in the water. Here are a few more:
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Water polo
Synchronised swimming
Sailing
Rowing
Diving
Scuba diving
Water skiing
and of course there are many more…
The link between water sports
and chemistry
The chemical link this module will explore between water sports and
chemistry is in fact the chemistry of solutions.
Using water as our example we encounter it in three states:
 As a solid – ice
 As a liquid – water
 As a gas – water vapour
We commonly encounter water as a liquid as this is the state it is in
under normal conditions, this means at room temperature and under
normal atmospheric pressure.
A recap of the states of matter is important so that we can explore
some of the chemistry behind solutions.
The link between water sports
and chemistry
A solid can sometimes be dissolved in a liquid. This
can give the appearance of the solid disappearing,
or can colour an otherwise clear solution.
The biggest source of liquid in the World are our seas
and oceans. Of course sea water is not pure water,
it is a solution with many different substances dissolved
in it, the most recognisable being sea salt.
Definitions associated with
solutions
In order to further explore solutions we must first understand some
Definitions associated with them.
A solution is a liquid which has a substance dissolved in it.
The substance dissolved in the solution is known as the substrate.
The liquid that substrate dissolves in is known as the solvent.
Water is known as the universal solvent because so many different
substrates will dissolve in it.
Salt and sea water
Sea water is salty, as we know.
The definition of a salt, in chemistry, is the product formed from the
neutralisation of acids and bases. When salts are dissolved in water they
are called electrolytes.
Solutions of electrolytes can conduct electricity, a property shared with
molten salts.
Common salt is sodium chloride (NaCl), used in cooking and found in
abundance in the Worlds’ seas although many other salts are also
present.
A mountain of salt from a refinery
Dissolving substances in a liquid
When a solid is added to a liquid it will either dissolve or it will
not. A substance which will dissolve in a liquid is known to be
soluble, one that will not is known to be insoluble.
Only a certain amount of a solid will dissolve in a liquid at a given
temperature. (You will have seen this in your experiment adding
salt to a beaker of water).
When no more solid will dissolve in a liquid the liquid is said to
be fully saturated and the solution which has been made is
known as a saturated solution.
Exploring solutions and their
physical properties
Having learnt some of the terms associated with solutions we can now
explore how this changes the chemical and physical properties of the
solutions.
(It is important to understand that a solution can also have a solid
suspended in it, this solid has not dissolved but has formed a mixture with
the liquid or solution).
When a solution has been formed it is ‘thicker’ than the original liquid. (In
fact the solution is more dense)
The more dense a solution is the greater the
resistance encountered by an object moving
through that solution.
Exploring solutions and their
Physical properties
The resistance encountered when an object moves
through a liquid is known as water resistance or drag
and it is a force that acts in the opposite direction to
the movement of travel of the object moving through
a solution.
This has a direct effect on our water sports. The
greater the resistance the swimmer, boat or diver, encounters when
moving through the solution the more energy they will have to expend
to over come this. If they were to expend the same amount of energy
moving through a less dense solution, they would move faster as they
would encounter less resistance.
Exploring solutions and their
physical properties
In terms of swimming, it therefore stands to reason that, it is considered
to be harder to swim through sea water than it is through pool water,
and thus times for swimming the same distances are slower in sea
water than in pool water.
Developments in sports equipment have tried to overcome some of the
effects of water resistance and this can be no where better highlighted
than in the sharkskin suits many professional swimmers now wear to
reduce drag.
Buoyancy
There is, however, an advantage to taking part in water sports in a
more dense solution such as sea water. Buoyancy, the affect of
floating, is actually increased in a more dense solution.
Gravity pulls an object downwards through a solution, whilst the
solution produces a force upwards in the opposite direction known as
up thrust.
These forces combined with a number of other factors, including how
dense the object is in comparison to solution and the shape of the
object, determine whether that object floats, sinks or is semisubmerged in the solution.
Buoyancy continued
An object with a constant weight and
shape, such as a boat, will sit higher
in a more saturated solution, such as sea
water, than it would in a less saturated
solution such as pool water.
The Dead Sea
A great example of where the saturation level of a liquid is very high is
The Dead Sea. Here there is roughly eight and a half times more salt
Dissolved in the seas’ water compared to other oceans and seas.
People have reported the strange phenomenon of floating far higher in
the water due to this.
This affect is important to our water sports because if less of an object
is submerged in a solution when moving through it, it will encounter
less drag than an object which is further submerged. This means than
an object can move through the solution faster with the same amount of
force.
Summary
Through exploring both the effects of drag, due to solutions being of
higher saturation, and buoyancy it is clear that the chemical and
physical properties of solutions can impact on our water sports, and
performances there in, to a large degree.
It is important to remember however that many of the differences seen
in our water sports between performances in the pool and in open
water are actually due to external factors such as weather conditions,
tidal effects, water temperature and visibility, as well as the chemical
and physical properties of the solutions themselves.
Worksheet answers Q1 – Q3
1. A solution is a liquid which has a substance dissolved in it. What is
a liquid that will dissolve a solid called?
A liquid that will dissolve a solid is called a solvent.
2. What does the term soluble mean and what is the opposite of the
term soluble?
The term soluble is given to a solid that will dissolve in a solvent.
The opposite of the term soluble is the term insoluble which means
something that will not dissolve in a solvent.
3. When a solution will dissolve no more solid it is said to be fully
saturated (fill in the missing word).
Worksheet answers Q4 – Q6
4. What is the universal solvent and why is it known as this?
Water is known as the universal solvent and it is called this because
so many substances will dissolve in it.
5. What is another term for water resistance?
Another term for water resistance is drag.
6. Does the density of a solution increase or decrease with an
increase in the saturation level of a solution?
The higher the saturation level of a solution the more dense the
Solution becomes.
Worksheet answer Q7
7. What factors can you suggest for why a swimmer may be faster in
a pool than in the sea, if swimming with the same effort? (Include
buoyancy and water resistance in your answer as well as two other
factors).
The saturation level of sea water is higher than that of pool water
due to the amount of salts dissolved in it. This means that a swimmer
has to swim through a more dense solution when swimming in the sea,
so encounters more water resistance or drag, thus slowing the
swimmer down, however the swimmer would be more buoyant which
would counteract this affect slightly. Other, and probably more
important factors include weather conditions, tidal effects and
differences in temperature and visibility of the pool water compared to
the sea water.