Sport & Water – The Chemistry of Solutions

1. Sport & Water – The Chemistry of Solutions

2. 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.)

3. 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: • Water polo • Synchronised swimming • Sailing • Rowing • Diving • Scuba diving • Water skiing and of course there are many more…

4. 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.

5. 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.

6. 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 solventbecause so many different substrates will dissolve in it.

7. 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

8. 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 saturatedand the solution which has been made is known as a saturated solution.

9. 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.

10. 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.

11. 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.

12. 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 semi- submerged in the solution.

13. 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.

14. 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.

15. 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.

16. Worksheet answers Q1 – Q3 • 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. • 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. • When a solution will dissolve no more solid it is said to be fully saturated (fill in the missing word).

17. Worksheet answers Q4 – Q6 • 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. • What is another term for water resistance? Another term for water resistance is drag. • 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.

18. Worksheet answer Q7 • 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.