The Effect Salt Has On The Boiling Point Of Water

Introduction

When boiling water, whether it be for pasta or some vegetables, it is always recommended to add salt into the water as the water begins to heat up to help speed up the boiling process. I will check to see whether or not this “cooking tradition” is effective or not, more specifically whether the salt actually affects the boiling point of water, by measuring the boiling point of 300ml of water at first without any salt and then gradually administrating teaspoons of salt to see if there is any variety between the results.

A liquid comprises of particles which are bonded closely together, however, they are able to move around each other significantly easier than those of solids. There are frailer forces between the particles of a liquid, which makes it virtually impossible for liquids to retain their own shape, this means the liquid will take up the shape of the container that it is being held in. Liquids contain more kinetic energy than any solid due to the weaker bonds but less energy than gases.

Gas particles, contrasting to those of liquids and solids, are completely separate and randomly arranged. The bonds that hold the particles together are tremendously weak which allows the particles to freely move in all directions at all times, this can cause the particles to collide with each other or onto the sides of the container that the gas is being contained in – this causes pressure.

Water boils when the molecules are able to break free from intermolecular attractions and overcome the vapour pressure of the surrounding air to turn from a liquid state, where water molecules are loosely held together by attractions, to a gaseous state, where these attractions are profusely weaker, to a point where molecules are able to freely move around. This occurs due to the introduction of thermal energy which animates the particles which causes the kinetic energy of those particles to increase. Once the kinetic energy within the particles become too substantial for the bonds to hold in place, the boiling water reaches a point where the bonds can no longer hold on and break away, releasing the molecules and converting the liquid into a gas.

I decided to use a saucepan for my experiment rather than another pot to boil the water because a saucepan is very efficient in distributing the heat being emitted from the boiling water and it is also smaller and more convenient for me to use, which in turn lowers the risk factor of this experiment which helps to improve my safety and the validity of the experiment.

Aim: To investigate whether or not salt affects the boiling point of water.

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Hypothesis: The more salt added to the water the higher the boiling point will be. This will mean that the water will take longer to boil once salt is added to it than before. This is due to the fact that the salt (sodium chloride) particles is affecting the chemical bonds between the oxygen and hydrogen atoms, so that more energy is needed to turn water into vapour, which in turn means It will take longer to boil.

When the salt content of the water increases, on account of the teaspoons of salt being added to the water, the boiling point of the water increases. This is evident in the results in the following ways: when there is no salt in the water the boiling point is only 95.250C, whereas when 4 teaspoons of salt is added to the water the boiling point increases to 1040C.

After salt is added to distilled water, a phenomenon known as “boiling point elevation” occurs. The process isn’t limited to only water though. In actual fact, the process transpires at any time when a non-volatile (dissolved) solute (salt) comes into contact with a solvent (for example; water). This is due to the fact that when the sodium chloride (salt) is completely dissolved into the solvent (water), the salt changes to charged sodium and chlorine ions. These stimulated particles alter the molecular structure of the bonds that envelop the water particles, this affects the ion-dipole interactions between the hydrogen and oxygen atoms.

An ion-dipole interaction is the electrostatic connection amongst a charged ion and molecule, which is a dipole. Each and every water molecule is considered to be a dipole, this means that one side of the molecules (oxygen) are more negatively charged than the other side (hydrogen). The positively charged sodium ions are attracted to these positively charged molecules and align with the oxygen atoms contained in the water molecules, and the negatively charged chloride ions are more attracted to the positively-charged hydrogen atoms. The ion-dipole interaction is considerably stronger than simply the hydrogen-based bonds of water alone, which means it needs more kinetic energy (heat) to influence the water molecules to convert to a gaseous state. Distilled water that contains the solute salt throughout it boils at a higher temperature for this very reason.

• a) The third trial of the 2 teaspoon amount of salt and the second trial of the 4 amount were outliers. The boiling point of each of these tests were considerably higher than the rest of the tests conducted with the relevant amount of salt. This occurred due to the fact that the amount of the salt distributed between each teaspoon may not have been equal, in this case it was more than the rest of the other test amounts.
• b) This error could have been improved by utilising the use of an object to ensure that each teaspoon had an equal amount of salt on it, therefore increasing the accuracy of the experiment. An example of an object that would work is a knife or a chopstick which could have been used to flatten out the teaspoon, ensuring an even amount of salt on each teaspoon.

In terms of a science experiment, reliability is defined as “the degree of consistency of each measurement with in an experiment”. A positive aspect of the experiment conducted is the fact that each amount of salt was tested 4 times. This reassures the fact that any effect triggered by any outliers would be recognised and neutralised, an example of this is the two outliers present in the experiment results (test 3 of 2 teaspoons and test 2 of 4 teaspoons), these results contained clear outliers which were disregarded in the making of the graph. The repetition of trials also negated the chance of arbitrary errors affecting the final average results and the trend of each experiment. A negative aspect of my experiment was the fact that each testing process was only repeated four times per amount. If I had decided to repeat each test 5 times it would have helped to solidify the overall reliability of my experiment. Overall my experiment was shown to be reliable, even though the reliability could have been increased by repeating the experiment five times as opposed to four, the experiment was still considered to be reliable due to the three repetitions that were done on each amount of salt.

Conclusion

To determine whether the hypothesis was true or not, the scientific experiment was carried out by measuring the boiling point of 300mL of distilled water in a saucepan and then proceeding to add specific amounts of salt to the water, the water with the salt incorporated in it then had its boiling point measured by the use of a thermometer. The results from this experiment portray that the boiling point of distilled water was 95.250C, which when compared to water with one teaspoon of water added to it had an average boiling point of 97.50C, this shows that the distilled water had a lower boiling point. To conclude, the results from this experiment support the hypothesis that salt does have an effect on the boiling point of distilled water, this effect is increasing the boiling point slightly every time more salt is added to it.

Bibliography

1. Owlcation. (2019). What Is the Particle Model: A Guide to Solids, Liquids and Gases. [online] Available at: https://owlcation.com/stem/what-is-the-particle-model [Accessed 24 Mar. 2019].
2. https://owlcation.com/stem/what-is-the-particle-model
3. https://van.physics.illinois.edu/qa/listing.php?id=1447&t=salt-and-the-boiling-point-of-water