Unit 5

5a.  Give a complete description of how someone can “suck” soda through a straw and explain why the word “suck” is somewhat misleading in this context.

  • “Sucking” a liquid through a straw is not as simple as one may think.  In actuality, you cannot “suck” a liquid.  The straw itself acts as a conducer for the soda to move through.  When you “suck” soda through the straw, you are actually moving air in your mouth out of the way and slightly lowering air pressure.  Now that the air is pressing down on the soda in the cup, it is forced up the straw (https://www.forbes.com/sites/quora/2018/01/08/why-drinking-straws-dont-work-in-space/#3b4a30b93c87).  This happens until the “sucking” stops, or until the pressure is equalized. 

5b.  Give a complete explanation of how we the “pressure fountain” demonstration worked in class.

  • In the flat-bottomed round flask, the water was in liquid form had been boiled into a hot gas form.  After BR put the straw with a stopper into the flask and took it off of the heat source (which had caused the water to boil), he flipped it upside down into a container of water.  The gas particles inside the beaker began to cool, condensing and contracting them; this allowed for water from the container to slowly seep through the straw into the beaker.  The air pressure in the room was pushing down on the water, and then allowed it to freely flow into the straw.  Once the water made its way into the beaker, more of it flowed furiously into the beaker until it was almost full because it cooled the gas in the beaker down.

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