Now it’s the time to announce the winners of the Amazing Trick contest, which ended on April 30th. Many thanks to those of you who sent their (more or less) lucky guesses, or knowledge bits. Not all of them were correct, but even the wrong ones were rewarded, because this blog uses the DoFollow plugin, thus offering commenters SEO accountable links to their sites.
The following entries qualified:
the air is hot around the flame, when putting the glass, a lot of hot air is captured
a time after the candle extinguishes, the air get cold down, as the volume and mass remain the same, the pressure inside goes down too
the pressure inside will be less than the pressure outside, and the water is pushed inside by the outside pressure
The hot air inside the glass is less dense (and thus at a lower pressure) than the cooler outside air. The difference creates suction, which pulls the water inside the glass.
The basic premise is the change in air pressure. When the open end of the cup is submerged in the water it creates a type of water seal preventing additional air from entering the space. When the candle is lit it begins to heat up the air around it, burning the oxygen up and according to Boyle’s law, when a gas (air) is heated its density is reduced. (This is the motive “force” behind hot air balloons by the way). The reduced density of the hot air in a closed container creates a vacuum.
The air pressure being exerted on the water outside of the jar is greater than that being exerted inside the jar so the water moves towards the path of less resistance and pushes itself inside. Technically if there were enough water and the candle was allowed to burn itself out, the water would fill approximate 1/5th of the volume available inside the jar since air is almost 20% oxygen.
Synopsis (I’d copy and paste but don’t want the duplicate content penalty )
1) Jar holds a finite amount of air
2) Candle heats up air
3) PV=nRT dictates that under finite volume hotter air increases pressure
4) High pressure air bubbles out of the jar
5) Candle burns out => air cools down
6) Air pressure in jar decreases
7) Water in jar rises until the pressure difference between the jar and the atmosphere equals the height of the column of water * density of water * gravity
All four entries are correct. Many thanks to all participants, and here we have the winners:
– One year free hosting for a domain: Mihai, Susan and Steve
– One free link to All Tips And Tricks plus one free review of her blog: Julie
The choice was made taking into consideration that Julie did not fully respect the terms of the contest (she did not link back to this site). However, because I liked her answer, I decided to give her the free review of her blog, as a consolation prize.
Congratulations to the winners! I’ll contact you via e-mail over the next few days, to arrange the details of your hosting accounts. You must have the domain names already bought, as the prize includes only the hosting.
More contests are coming soon! If you don’t want to miss them, make sure you subscribe to my feed.