Add a Pinch of Salt


| 2 Comments

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While listening to two of my roommates bicker over whether or not the myth of adding salt to water makes it boil faster I began to also wonder whether or not it was true. My one roommate, Athyna, supported the null hypothesis of that adding salt to a pot of water actually did nothing while my other roommate, Emilie, supported the alternative hypothesis saying that adding salt to a pot of water does cause it to boil faster. I on the other hand also threw out the idea that there may be confounding variables that allow you to believe that the water is boiling faster. I said that the unaccounted factor might be your mind. This placebo affect changes Emilie's perception of the boiling water because it causes her to think that there is less time going by as she boils water. By adding the salt to the pot of water Emilie may believe that the water is boiling faster in order to reduce dissonance from her original belief when in fact the boiling water could just occur by chance. Maybe she uses less water than Athyna; she could also be more distracted while cooking than Athyna and her completing other tasks may cause her to think that the water boiled relatively fast.

A scientific study that was performed was helpful because it provided a chemical explanation for the failure to reject the null hypothesis. The study showed that if you took two identical amounts of water and added salt to one then the pot with salt will not boil any faster than the pot without salt. The chemical explanation dealt with water's heat capacity. Although with 100 grams of water 80 grams contains pure water and 20 grams contains pure salt; the mixture would have a lower boiling point than pure water. "Please note that this will not hold true if you take two identical pots containing one gallon of water each and add the salt to one pot because then the volume of liquid in the salted pot will be greater than the one gallon starting point." The study was helpful because if you truly wanted to have a pot of water boil faster then you could do so by adjusting the proportions of salt and water in the pot.

Another study explains the hypothesis of whether or not salt helps water boil faster in terms of the vapor pressure in the presence of a solute. The addition of the salt content to the water "lower's the vapor pressure which means that a higher temperature is necessary to boil the water in the solution, hence boiling-point elevation."  On a positive note the study provided a possible confounding factor of a higher temperature that may have caused Emilie to believe her pot of water with salt in it boils at a faster rate than a pot without salt. The study was not helpful though in terms of providing truth to reject or fail to reject the null hypothesis in terms of boiling speed.

A third study provided truth in rejecting the null hypothesis concluding that there is a significance with the addition of salt added to a potential pot of boiling water. The experimenter provided evidence from an experimental study conducted and explained "when salt is added to the mix, the molecules start to move around rapidly and randomly making the water temperature rise and the water to boil faster." The study was unhelpful in terms of the consistency of each pot used. I was unable to tell if they had less water and a specific portion of salt in a pot as the first study had shown, or if both of the pots contained the same amount of water and the other just added salt.

With the chemical reasoning from each study I myself concluded to neither fail to reject or reject the null hypothesis. I believe that the speed of the water boiling with the addition of salt has to do with heat capacity. All three studies seem to agree on the fact that when salt is added to water its heat capacity rises allowing it to boil at a greater temperature. So therefore I am now faced with the task of informing my roommates that they were both wrong because salt only affects the temperature at which water boils not the speed. But what do you think? Is it the salt that helps the water boil faster because of the molecules bouncing around? Do you believe that the same results would hold true if a different compound was used in the place of salt? 

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2 Comments

Hi Laura! I would first like to let you know that I really enjoyed reading your post and liked how you combined information from class lecture with your own material. With that being said I am a person that adds salt to water to help it boil faster, this is something that I have always accepted as a fact because for as long as I can remember anyone who has ever boiled water in my family has always added salt in first. Your blog post opened my eyes and now has me thinking that salt may not contribute to the boiling rate of water. I liked how you used three different studies to back up your opinion, and now I almost believe that salt slows down the speed at which water boils if your theory is correct. In your final paragraph you talk about how you feel as though salt contributes to waters heat capacity, meaning that water will now boil at a hotter temperature rather than the 212 degrees fahrenheit that we know it to boil at. So if salt allows water to boil at a higher temperature meaning anything above 212 degrees wouldn't that take a longer period of time? However, if it does not take a longer period of time then that would mean that water boils at a faster rate with salt. Overall it doesn't appear that anything is conclusive, therefore I will continue to add a couple pinches of salt to my water before boiling just incase it does in fact increase the speed at which the water boils. Overall I really enjoyed reading your blog post, it forced me to think on a deeper level and felt as though I was sitting in an orange chair right in Andrew's classroom.

This post was different from others I have read, I was never aware of salt helping water boil faster or slower. When my mom makes spaghetti she adds salt to the water after it's already come to a boil to add taste to the spaghetti. After reading your hypothesis and seeing the results, I agree with Jonathan that the results are kind of inconclusive so if you add salt in your water or not it doesn't seem like the water will come to a boil faster or not. This blog was interesting since I've never heard of this theory before and it was a different way to explain the salt in the water since you did an experiment with it and found out if your friends hypothesis was correct or not!

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