For many chemistry lessons are a real torment.But if you know something in this thing, you can spend an entertaining experience and enjoy it.And teachers can not hurt to interest their students.To do this, perfectly suited the so-called Pharaoh's snakes.
origin of the name
authentically origin of the name "Pharaoh's snakes" No one knows, but the Times his biblical events.In order to impress Pharaoh, the prophet Moses on the advice of the Lord threw his staff on the ground, and it became a serpent.Once in the hands of the favorite reptile became a staff again.Although in reality between how these experiments are obtained, and biblical events have nothing in common.
From what we can get, "Pharaoh's snakes"
most common material for the snakes is a mercury thiocyanate.However, experiments with them can be carried out only in a well-equipped chemical laboratory.The substance is toxic and has an unpleasant odor resistant.A "Pharaoh's serpent" in the home can be created out of tablets that are sold at any pharmacy without a prescription, or fertilizer from the hardware store.For the experiment using calcium gluconate, methenamine, soda, powdered sugar, nitrate and many substances that can be purchased at a pharmacy or store.
"Snake" of tablets containing sulfonamides
easiest way to stay at home experience "Pharaoh's snakes" of sulfa drugs group.That means such as "Streptocide" "Biseptolum" "Sulfadimezin" "Sulfadimetoksin" and others.These drugs are in almost every home."Pharaoh's snakes" of sulfonamides obtained shiny gray structure they resemble corn sticks.If carefully clamp or forceps to pick up the "head" of the snake, you can pull out of a pill long enough reptile.
In order to conduct chemical experiments "Pharaoh snake", you will need the burner or dry fuel and the above drugs.Several tablets laid out on a dry alcohol, which ignited.With reaction includes such substances as nitrogen, sulfur dioxide, hydrogen sulfide and water vapor.The following reaction formula:
S11H12N4O2S + 7O2 = 28C + 2H2S ↑ + 2SO2 ↑ + 8N2 ↑ + 18H2O
Such experience should be done very carefully, because the sulfur dioxide is highly toxic, as well as hydrogen sulfide.Therefore, if you can not be aired during the experiment room or turn the hood, it is better to do it on the street or in a specially equipped laboratory.
"Snake" of calcium gluconate
best to conduct experiments of those substances which are safe, even when used outside of a specially equipped laboratory."Pharaoh snake" of calcium gluconate is obtained simply.
To do this, take 2-3 tablets of the drug and a cube of dry fuel.Under the influence of the flame reaction begins, and from the tablet creeps gray "snake."Such experiments with calcium gluconate is quite safe, but it's worth to be careful in their conduct.The formula of a chemical reaction follows:
C12H22CaO14 + O2 = 10C + 2CO2 ↑ + CaO + 11H2O
As you can see, there is a reaction with the release of water, carbon dioxide, carbon and calcium oxide.It causes gas evolution and growth."Pharaoh's snakes" are obtained in up to 15 centimeters, but they are short-lived.If you try to take them in hand they split.
"Pharaoh snake" - how to make fertilizer?
If you have a vegetable garden on the farm or cottage, be sure there are different fertilizers.The most common, which can be found in the pantry of any summer resident and farmer - nitrate or ammonium nitrate.To experience required sifted river sand, half a teaspoon of ammonium nitrate, a half teaspoon of powdered sugar, a spoon of ethyl alcohol.
necessary to make a hill of sand deepen.The larger the diameter, the thicker the "snake".Well rubbed a mixture of ammonium nitrate and sugar poured into the recess and pour ethyl alcohol.The alcohol was then set on fire, gradually formed "the snake".
reaction with the following occurs:
2NH4NO3 + C12H22O11 = 11C + 2N2 + CO2 + 15H2O.
Liberation of toxic substances in the experience obliges to observe safety precautions.
"Pharaoh snake" of food
"Pharaoh's snakes" are obtained not only from medicines or fertilizers.For the experiment, you can use products such as sugar and soda.Such components exist for every kitchen.From river sand hill formed with a recess, and is impregnated with alcohol.Sugar and baking soda were combined in a ratio of 4: 1, and poured into the recess.The alcohol is ignited.
mixture begins to blacken and swell slowly.When the alcohol is practically ceases to burn, sand creeps few crinkly "reptiles."The reaction of the following:
2NaHCO3 = Na2CO3 + H2O + CO2,
C2H5OH + 3O2 = 2CO2 + 3H2O
mixture decomposes to sodium carbonate, carbon dioxide and water vapor.It gases are forced to swell and grow soda ash, which is not consumed during the reaction.
Another "reptile" from the tablet
There is another simple way to get the "Pharaoh's serpent" of drugs.This will require the purchase at the pharmacy drug "Urotropin."Instead, tablets can also be used dry fuel containing this substance.Still need a solution of ammonium nitrate.The drug "Urotropin" it is necessary to impregnate them.However, one can immediately be applied to the entire raw material solution, so it is necessary to add a few drops and dried.In this drying should occur at room temperature.
After that ignited the tablet.The result is not so much a "snake" as "the dragon."However, if you look, it's the same experience, "Pharaoh's snakes."But because of the properties of the components is more violent reaction, which leads to the formation of three-dimensional figures.
"Snake" of mercury thiocyanate
first chemical experience, "Pharaoh snake" has turned from a medical student in 1820.Friedrich Wohler mixed solutions of mercury nitrate and ammonium thiocyanate and received a white crystalline precipitate.The resulting precipitate thiocyanate mercury student dried and set on fire just for the sake of curiosity.From beginning to crawl out of the burning matter of black and yellow snake mass.
"Pharaoh's snakes" of mercury thiocyanate obtained easily.The substance is necessary to set fire to a heat-resistant surface.Subsequent reaction:
2Hg (NCS) 2 = 2HgS + C3N4 + CS2
CS2 + 3O2 = CO2 + 2SO2
under thermal influence decomposition thiocyanate mercury to mercury sulphide (attached "reptile" black), carbon nitride (answersyellow color for snakes) and carbon disulfide (carbon disulfide).Last flares and splits into gas - carbon dioxide and sulfur dioxide, which is expanded carbon nitride.He, in turn, captures the mercury sulfide, and the resulting black-yellow "Pharaoh's snakes."
This experience is by no means impossible to carry out at home!Besides being toxic gases, mercury vapor is released.Mercury is toxic in itself, and can cause severe chemical poisoning.
Security in experiments
Despite the fact that most of the substances of which may turn out, "Pharaoh's snakes," considered to be safe, the tests should be carried out very carefully.As can be seen from the above formulas, decomposition allocated fairly toxic components, which can lead to severe poisoning.All experiments can be carried out at home only in a ventilated area or in the presence of high power extraction.Experiments with mercury thiocyanate can be carried out only in specially equipped laboratories, observing all safety rules.
In conclusion we can say that by conducting chemical experiments in the classroom, "Pharaoh's snakes", the teacher may be interested in the subject of your students.The lesson is likely to be interested, even those who do not understand and do not like chemistry.And those who prefer to practice instead of boring theoretical calculations, will receive an additional stimulus to the study of science.