The contraction and relaxation of the mercury is due to changes in the surface tension of, and charge on, the mercury drop. When the mercury is not in contact with the iron nail, it's surface becomes oxidized and the positive mercury ions repel each other, causing the mercury pool to relax (ie. lower its surface tension). The relaxation causes the mercury to come into contact with the iron nail, which has a sufficiently negative electrochemical potential to reduce the mercury ions to mercury metal. The surface tension of the mercury increases and the pool contracts, causing the contact with the nail to be broken. The mercury surface reacts with the acid and becomes oxidized again, thereby, completing one cycle of the oscillation.
28 Feb 2011
25 Feb 2011
Alkali metals and water
from scientist303
Alkali metals react with water reducing its protons to H2(g) and leaving an alkaline aqueous solution due to alkali metal hydroxide formation. When going down in the group from lithium to cesium the alkali metals give its electrons to the protons of water more easily and the reaction goes faster. As the reaction release heat, if this heat cannot be dissipated quickly enough the hydrogen released will get ignited, sometimes very violently, and react with atmospheric oxygen forming water again.
M(s) + H2O(l) = M(OH)(ac) + 1/2 H2(g) + lots of energy(*)!!...
H2(g) + ½ O2(g) + ignition energy(*) = H2O (g)!! + lots of energy!!...
Alkali metals react with water reducing its protons to H2(g) and leaving an alkaline aqueous solution due to alkali metal hydroxide formation. When going down in the group from lithium to cesium the alkali metals give its electrons to the protons of water more easily and the reaction goes faster. As the reaction release heat, if this heat cannot be dissipated quickly enough the hydrogen released will get ignited, sometimes very violently, and react with atmospheric oxygen forming water again.
M(s) + H2O(l) = M(OH)(ac) + 1/2 H2(g) + lots of energy(*)!!...
H2(g) + ½ O2(g) + ignition energy(*) = H2O (g)!! + lots of energy!!...
24 Feb 2011
Acetylene Explosion
why in spain chemistry lectures are not like that???
2 HCCH + 5 O2 = 4 CO2 + 2 H2O
2 HCCH + 5 O2 = 4 CO2 + 2 H2O
22 Feb 2011
Watermelon versus liquid nitrogen
from mattmcc1234
Liquid nitrogen, with a boiling point of -195.79 °C, just does not like to remain liquid at room and evaporates inside a coke bottle generating lots of pressure...very impressive!!
Liquid nitrogen, with a boiling point of -195.79 °C, just does not like to remain liquid at room and evaporates inside a coke bottle generating lots of pressure...very impressive!!
Microwavable Grape Plasma
It is relatively easy to generate a plasmoid using a microwave and a medium that will initiate the formation of a plasmoid, this can be caused by the carbon microparticles in the smoke from a naked flame or match, which ignites and moves about as plasmoids, and some biological cells are known to produce plasma under microwave conditions, such as grapes (electrons try to move through highly resistive grape-skin, and plasmoids may form) This is due to the fact that microwaves, being high frequency electromagnetic radiation in the GHz range, are capable of exciting electrodeless gas discharges in air, similar to the process used in Sulfur lamps.
21 Feb 2011
HIGH SPEED EXPLOSIONS
A comparison of the fuel-air flame speeds in butane/air and hydrogen air mixtures
20 Feb 2011
NUCLEAR CHAIN REACTION
Representation of a nuclear chain reaction using ping pong balls and mousetraps
17 Feb 2011
16 Feb 2011
15 Feb 2011
OSCILLATING REACTION
Very complicated cascade of reactions. Here's how it works: http://chemistry.about.com/cs/demonstrations/a/aa050204a.htm
14 Feb 2011
Carbonized sugar
by koen2all
This is the dehydration of sugar (sucrose) with sulfuric acid. The sulfuric acid removes water from the sugar in a highly exothermic reaction, releasing heat, steam, and sulfur oxide fumes. Aside from the sulfurous odor, the reaction smells a lot like caramel. The white sugar turns into a black carbonized tube that pushes itself out of the beaker...
This is the dehydration of sugar (sucrose) with sulfuric acid. The sulfuric acid removes water from the sugar in a highly exothermic reaction, releasing heat, steam, and sulfur oxide fumes. Aside from the sulfurous odor, the reaction smells a lot like caramel. The white sugar turns into a black carbonized tube that pushes itself out of the beaker...
13 Feb 2011
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