Welcome back! Today I would like to share with you why I decided to get on the scientific pathway.
I have always been fascinated by nature in general and animals. I remember, as a kid, my dream was to become a vet, in order to save the precious life of our beloved house pets but also to cure weird and exotic animals all over the world. However, as soon as I realised that being a vet involved to anaesthetise and operate animals, but also possibly put them down to avoid pointless sufferance, I put my future vet career aside and decided to look around for something less bloody and possibly less heart breaking.
Even though I have always been a keen student and I have always worked very hard even on subjects that were as far away as possible from science, nothing in particular seemed to make me say the words: “Wow! That’s what I want to do for the rest of my life”. Nonetheless, I kept watching many documentaries and I kept being interested in everything that was “nature” related.
It was only when I started the third year of high school that I got hooked by what we can define “the real science”. I still remember the first day my Chemistry and Biology high school teacher entered in the class and, after taking the attendance, she asked us a really difficult question: “Why do you think it is important to study Chemistry?”. Everybody seemed a little bit confused by this question: obviously nobody ever asked (or even better, explained) us why we had to study Italian literature, Physics or learn ancient Greek and their importance for the lives of teenagers, too focused on trying to deal with pubescence in the South of Italy. Anyhow, she asked us that question and after few minutes of silence and weird looks in between us kids, she started talking: “The fact that you guys are listening/thinking/looking lost is due to electric signals going around in your brain thanks to chemicals being released. EVERYTHING that you do, from the moment you were born is a chemical process. From the origin of the universe to this right moment chemistry and physics have driven and will be driving everything around us and it is best to proper understand how these two work.”
Clearly the looks on our faces were in between astonishment and misunderstanding. It is kind of difficult to catch every teenagers’ attention mentioning electric signal and the origin of the universe, but she continued: “If you still are not convinced about the importance of Chemistry and Biology in your life, just think about the pasta you guys will have for lunch (Italian stereotype, but still, this is the example she made!). I think all of you will be hungry and in a hurry to eat, so let’s think about when it is the best moment to add the salt to the water: before or while the water is boiling?”
And to answer this question I would like to (hopefully) easily summarise the basic principle behind the best moment when to add the salt in the pasta water.
“Science Related Fact” (SRF):
Let’s briefly recapitulate the fundamental states of matter: solid, liquid and gas. The main difference in between these states is the strength of the bonds holding the molecules together: in the solid state these bonds are very strong, in the liquid one the bonds are more loose, while in the gas state there are virtually no bonds in between the molecules. The transition between the different states depends on the energy we give the the system, allowing for the molecules to start moving and loosing up their reciprocal bonds.
When we heat up the water in the pot, we give the water molecules energy to make them transitioning to the gas state, until all the molecules have sufficient energy to become aqueous vapor and the water starts to boil. This happens at the so-called boiling point, that for the pure water is 100°C. When we add salt to the water, the molecules of salt, composed by the two ions sodium and chloride, get literally in the way of the water molecules during the transition to the gas state. Since salt physically impedes the water to leave the liquid phase, the boiling point will be higher than 100°C, even though the effect is pretty small, due to the low quantity of salt used. Moreover, the process of salt dissolution in water, that consists in the water molecules surrounding the salt’s ions to separate their bond, requires heat: if we would measure the temperature of water before and after the addition of salt, we would find out that the temperature is higher before.
Due to this increase in the boiling point and the heat needed by the water to dissolve the salt, if you are really hungry and are looking forward to eat your pasta soon, the best moment to add the salt in the water is while it is boiling, a bit before adding the pasta. In this moment, the addition of salt will not affect the boiling point of water (it is already boiling!) and the decrease in the temperature due to the salt’s dissolution will be neutralised by the heat present at the boiling point.