What happens if we put a soap in a microwave ? What we observe in this experiment that we can carry out in our house is something very similar to what happens when we make popcorn in a microwave. This appliance is nothing more than a generator of electromagnetic radiation in the range of microwaves (hence its name), the same ones used by airport radars, the GPS in our cars, bluetooth, wi-fi …
But why do they heat the water for tea or milk for breakfast? In essence, the microwaves generated in the oven (and that remain contained in it) cause the water molecules to begin to vibrate, thereby increasing the temperature. Let’s not forget that what we measure with our thermometers is nothing more than the visible reflection of the thermal agitation of the subatomic world : the hotter a material is, the greater the vibration to which its atoms are subjected.
Well, what happens in the experiment is that the soap contains small air bubbles trapped inside , where there is also water vapor. The water vapor heats up, causing it to expand and increase the pressure on the bubble wall. In addition, since the soap softens due to the increase in temperature, it is easier for it to deform in the way we have seen. Ultimately, what we have here is an example of physical change, in which no chemical reaction is involved.
Does it work with any soap? Yes, but the effect is more fantastic in those soaps that have a large amount of these air bubbles. We can recognize them by putting them in water: if it floats, that’s ours!
What happens if we put a raisin in a soda bottle?
We all know that the buoyancy of a body in a fluid depends on the relative density between the two. If the object is denser than the fluid, the fluid will sink. If not, it will float. The density of a raisin is greater than that of water , and therefore one expects it to sink. However, when we did the test in a container with soda or any carbonated drink we observed the result of this experiment.
What’s going on? Soda is nothing more than water to which high pressure carbon dioxide has been added (in addition to other components to give it that characteristic flavor) that causes it to dissolve in the water. It is precisely this gas that forms tiny bubbles on the surface of the raisin, which end up functioning as floats. When the bubble reaches the surface, it bursts and the raisins sink again.
In essence, we are witnessing in a bottle what happens when you want to refloat a sunken ship .
To find out more: the world’s first soft drink
Joseph Priestley (1733-1804) is a clear example of the radical and liberal scientist who flourished in France and England during the second half of the 18th century. The son of a Yorkshire tailor, he was raised to become a Protestant pastor. A radical humanist, scientist and politician, Priestley entered the field of research thanks to Benjamin Franklin, who suggested that he write aHistory and current state of electricity, with original experiments. A keen-minded man, he carried out his research in his laboratory in Leeds, where he served as a parish priest since 1767. Being a simple amateur who did not have the money to invest in expensive devices, he was forced to develop the ingenuity and build himself the necessary instruments.
In 1771 the famousCaptain Cookhe offered him the position of astronomer on his second expedition, having been impressed by Priestley’s early work in optics and astronomy. Unfortunately, his religious and political ideas cost him his job. But Priestley was not discouraged. He decided to do something that would contribute to the success of the expedition. His interest in investigating the characteristics of all the gases that fell on his hands had led him to a brewery near his home in Leeds. There he discovered an interesting property of the carbon dioxide released during the fermentation of beer. If you left a plate of water on top of the jar, it would acquire a pleasant, acidic flavor that was reminiscent of Seltz waters. A short time later, he discovered that he could obtain the same results by pouring the water from one glass to another on top of the jar for three minutes. The experiments convinced him that its medicinal qualities – in particular to treat scurvy – were due to the gas dissolved in it, and in 1772 he patented a mechanism that “impregnated” the water with it. Captain Cook installed him in theResolution and in theAdventure in time for the trip. On my own merits,soda waterbecame thefirst commercial success of the new chemistry. Poor Priestley did not see the commercial benefits his invention could have, but another amateur scientist and Swiss watchmaker did: Johann Jacob Schweppe (1740-1821).
Miguel Angel Sabadell
