YOUCHEMISTRY: February 2012

29 Feb 2012

Lightbulb in liquid nitrogen

from TheBlueginjava



A bare wolfram lightbulb filament in a beaker of liquid nitrogen can be connected to an electric current safely and without decomposition of the filament, shining as a normal lightbulb. The liquid nitrogen is a non conductive and almost inert material that isolates the wolfram filament from the atmospheric oxygen that would burn it out. The video explains it very well!!

25 Feb 2012

Liquid Nitrogen Explosion

Steve Spangler Science




Liquid nitrogen (boiling point -196 ºC) evaporates very quickly (explosively) in contact with hot water....

Brainiac Alkali Metals

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!!...

Plastic sulfur

from chemToddler



I have never seen this typical lab demonstration so well performed!!....the most amazing thing is that this grouse black polymeric sulfur goes back to its yellow powdery S8 form if you give it some time...

23 Feb 2012

SUGAR AND KClO3

from nuclearrabbit




Under thermal conditions or ignited by sulfuric acid, KClO3(s) decomposes to KCl(s) and 3/2 O2(g), which is a disproportionation reaction. The O2(g) generated oxidises very quickly carbohydrates as sucrose, C12H22O11(s,) liberating lots of heat, CO2(g) and H2O(g)...the presence of a bit of CuCl2(s) gives the bluish colour to the flames...very spectacular!!...

21 Feb 2012

Conductivity of Glass

from NatSciDemos

Insulating glass becomes a conductor of electricity when heated with a blowtorch.

At the beginning I thought it was a fake as when heating the remains of the broken bulb, the two metallic filaments inside it were put into contact again. However, the changes observed on the intensity of the working bulb when changing the temperature of the "glass switcher" make me thought that this is well real!!




Two ceramic lightbulb sockets are wired in series to a household AC power cord. When two incandescent bulbs of the same Wattage rating are screwed into the sockets and the cord is plugged in, they both pass the same amount of current and so they both light with the same intensity. When one bulb is unscrewed, the circuit is broken and the other bulb goes out. If we can replace the missing bulb with a conductive material, the circuit will once more be complete and the remaining bulb will light again.

14 Feb 2012

Thermoelectric generator

from henders007



The thermoelectric effect refers to phenomena by which either a temperature difference creates an electric potential or an electric potential creates a temperature difference. Converting temperature to current is known more specifically as the Seebeck effect.

This effect has been used for decades to power space vehicles (Apollo ,Voyager probes, Mars rovers, etc..) using radioisotope thermoelectric generators, where the heat released by the radioctive materials is converted into electricity using an array of thermocouples.

Commonly used thermoelectric materials in such applications are semiconductors, as for example bismuth telluride (Bi2Te3).

What are the car companies waiting for to install these devices in our cars!!

13 Feb 2012

Giant Smoke Rings

Remote-controlled smoke rings!!!...VERY FUNNY!!

11 Feb 2012

HYDROGEN AND CHLORINE

from chempics

H2 + Cl2 = 2 HCl

For the reaction to start an initiator is needed in order to overcome the activation energy. This can be a flame (as in this video) or just UV light...

VERY NICE LABCOAT by the way!!!

8 Feb 2012

FARTING DRY ICE

from Chazmolanicus

The rapid expansion of CO2 when dry ice comes into contact with another surface results in some interesting sounds as it tries to escape.....really FUNNY!!