ice2.txt
ice2.txt - - - - meth805.zip\txt\pnt Heat from cold wood ashes,Slaking Lime,
The Thermit(e) reaction,Making your own hand-warmer,
goal:safe, portable heating up on the glacier. by Exothermic and endothermic
chemical-reactions. When a chemical reaction takes place, chemical bonds in
the reactants are broken and new bonds are formed. Depending on the nature of
the bonds involved, a reaction will either release energy to, or absorb energy
from, the surroundings, as heat. When a process releases energy to the
surroundings it?s called exothermic (from the Greek thermo meaning heat, and
exo meaning outside). The best seen 'exo' is a rise in the temperature of the
mixture. but, some processes soak heat-energy from the surroundings, they are
endothermic reactions (endo in Greek, means within). The best example of an
'endo' is a fall in the temperature of the mixture.
All combustion-reactions(eg. burning of coal) are exo. know this, the
reaction between iron and moist air to produce rust is very exo. and generates
lots of heat. but so slowly its undetectable. but, Pyrotechnics, explosives
and fuels, all have a very fast exo. For our hand warmer, do we need to use
an exo. or an endo. process? To make heat and release it to the room,
we need an exo.process and one that fits a hot pack for warming the hands. it
must be portable and easy to renew. make and keep heat, not hot nor too cold.
and safe, and not use hazardous chemicals.
We will try three different exothermic processes: 1.Heat from cold wood ashes
2.Slaking lime , 3.The thermit(e) reaction.
Heat from cold wood ashes: is dissolving potassium carbonate (K2CO3) in water.
Potassium-carbonate is one chemical left behind in the ashes of burnt wood.
You can extract it by boiling ashes in water and filtering off any solids.
The potassium carbonate dissolves in the water, along with some other salts.
evaporate off much water, and filter it (a cloth?), this will leave a clear
liquid, mostly potassium-carbonate. If you evaporate off nearly all the water,
solid potassium-carbonate will fall out. It can then be dried.
When we dissolved our dry, solid p-c in water, a rise of only a few degrees
Celsius occured. so its no suitable for our purposes. dissolving p-c in water
is an exo. but not a chemical reaction, because no chemical bonds are broken
or formed. But it generates heat, so its an exo.
Slaking lime: slaking of quicklime, has a chemical reaction or two.. We took ordinary chalk (calcium carbonate, CaCO3) and heated between 1,200and1,400C. At this heat the calcium carbonate releases carbon dioxide gas (CO2) and is
changes to quicklime (calcium oxide, CaO). When you add water to the
quicklime, a process called slaking, a reaction takes place, and lots of heat. The product is a compound,slaked-lime (calcium hydroxide, Ca(OH)2).
soluctions of 'slaked' lime are alkaline, but represent lo caustic hazard. Given enuff lime, the heat will be suitable, portable and reproducible.
The thermit(e) reaction(sometimes spelt thermite).
This is a strong + hi exo.reaction, used to weld railway lines together. higher than 1,600C. The thermit reaction is the reduction (reduction is/was the chemical removal of oxygen from, or the addition of hydrogen to, a compound. Reduction is more accurately known as a process in which atoms, molecules or ions gain electrons) of certain metal oxides by aluminium (Al) powder. We got our aluminium powder by filing down old drinks cans. We chose to use iron(III) oxide, or Fe2O3, known as rust. We got ours off an old corrugated iron shed at the sawmill. When we mixed our aluminium powder and rust in the right proportions, and kick-started the reaction, a glowing mass of molten iron was formed, along with an amazing amount of heat and light.
(read also about carbon-rod arch-lamps, arch-welders?)
This was a little too much a reaction to be used in making hand warmers.
The best reaction for use in our hand warmers was the slaking of lime. It
generated enough heat for our purposes, and involved chemicals (water, calcium-oxide and calcium-hydroxide) that are safe, and available.
TO MAKE YOUR OWN HAND WARMER YOU WILL NEED :
2 sealable polythene bags (approx. 10cm × 10cm)
14g powdered lime (calcium oxide), 10cm3 of tap water, a teaspoon,
plastic pipette or eye dropper, and a bucket of cold water
Before you try the following experiment, make sure that you are wearing
protective glasses nd latex or rubber gloves. Do NOT handle these chemicals with your bare hands. Don?t use a Nylon garment.
NOTE: Be careful: when mixing the contents you may find they become so hot, they may cause serious burns.
Take a small, self-sealing polythene bag and place it inside another bag of the same type and size. Using the teaspoon, carefully add 14g of powdered lime to the inner bag, and use the pipette or eye-dropper to add about 10cm3 of water to it. Seal up both bags securely, and mix the contents together by
carefully manipulating the powder and the water with your fingers. After a few seconds, you will notice that the temperature of the hand warmer.
we found that so much heat was generated by them that some of the
plastic bags actually melted. If this happens when you try the experiment, drop the bags into a bucket of cold water and dispose of the resulting solution. Be sure to wash your hands in plenty of cold running water.
-no end-
The Thermit(e) reaction,Making your own hand-warmer,
goal:safe, portable heating up on the glacier. by Exothermic and endothermic
chemical-reactions. When a chemical reaction takes place, chemical bonds in
the reactants are broken and new bonds are formed. Depending on the nature of
the bonds involved, a reaction will either release energy to, or absorb energy
from, the surroundings, as heat. When a process releases energy to the
surroundings it?s called exothermic (from the Greek thermo meaning heat, and
exo meaning outside). The best seen 'exo' is a rise in the temperature of the
mixture. but, some processes soak heat-energy from the surroundings, they are
endothermic reactions (endo in Greek, means within). The best example of an
'endo' is a fall in the temperature of the mixture.
All combustion-reactions(eg. burning of coal) are exo. know this, the
reaction between iron and moist air to produce rust is very exo. and generates
lots of heat. but so slowly its undetectable. but, Pyrotechnics, explosives
and fuels, all have a very fast exo. For our hand warmer, do we need to use
an exo. or an endo. process? To make heat and release it to the room,
we need an exo.process and one that fits a hot pack for warming the hands. it
must be portable and easy to renew. make and keep heat, not hot nor too cold.
and safe, and not use hazardous chemicals.
We will try three different exothermic processes: 1.Heat from cold wood ashes
2.Slaking lime , 3.The thermit(e) reaction.
Heat from cold wood ashes: is dissolving potassium carbonate (K2CO3) in water.
Potassium-carbonate is one chemical left behind in the ashes of burnt wood.
You can extract it by boiling ashes in water and filtering off any solids.
The potassium carbonate dissolves in the water, along with some other salts.
evaporate off much water, and filter it (a cloth?), this will leave a clear
liquid, mostly potassium-carbonate. If you evaporate off nearly all the water,
solid potassium-carbonate will fall out. It can then be dried.
When we dissolved our dry, solid p-c in water, a rise of only a few degrees
Celsius occured. so its no suitable for our purposes. dissolving p-c in water
is an exo. but not a chemical reaction, because no chemical bonds are broken
or formed. But it generates heat, so its an exo.
Slaking lime: slaking of quicklime, has a chemical reaction or two.. We took ordinary chalk (calcium carbonate, CaCO3) and heated between 1,200and1,400C. At this heat the calcium carbonate releases carbon dioxide gas (CO2) and is
changes to quicklime (calcium oxide, CaO). When you add water to the
quicklime, a process called slaking, a reaction takes place, and lots of heat. The product is a compound,slaked-lime (calcium hydroxide, Ca(OH)2).
soluctions of 'slaked' lime are alkaline, but represent lo caustic hazard. Given enuff lime, the heat will be suitable, portable and reproducible.
The thermit(e) reaction(sometimes spelt thermite).
This is a strong + hi exo.reaction, used to weld railway lines together. higher than 1,600C. The thermit reaction is the reduction (reduction is/was the chemical removal of oxygen from, or the addition of hydrogen to, a compound. Reduction is more accurately known as a process in which atoms, molecules or ions gain electrons) of certain metal oxides by aluminium (Al) powder. We got our aluminium powder by filing down old drinks cans. We chose to use iron(III) oxide, or Fe2O3, known as rust. We got ours off an old corrugated iron shed at the sawmill. When we mixed our aluminium powder and rust in the right proportions, and kick-started the reaction, a glowing mass of molten iron was formed, along with an amazing amount of heat and light.
(read also about carbon-rod arch-lamps, arch-welders?)
This was a little too much a reaction to be used in making hand warmers.
The best reaction for use in our hand warmers was the slaking of lime. It
generated enough heat for our purposes, and involved chemicals (water, calcium-oxide and calcium-hydroxide) that are safe, and available.
TO MAKE YOUR OWN HAND WARMER YOU WILL NEED :
2 sealable polythene bags (approx. 10cm × 10cm)
14g powdered lime (calcium oxide), 10cm3 of tap water, a teaspoon,
plastic pipette or eye dropper, and a bucket of cold water
Before you try the following experiment, make sure that you are wearing
protective glasses nd latex or rubber gloves. Do NOT handle these chemicals with your bare hands. Don?t use a Nylon garment.
NOTE: Be careful: when mixing the contents you may find they become so hot, they may cause serious burns.
Take a small, self-sealing polythene bag and place it inside another bag of the same type and size. Using the teaspoon, carefully add 14g of powdered lime to the inner bag, and use the pipette or eye-dropper to add about 10cm3 of water to it. Seal up both bags securely, and mix the contents together by
carefully manipulating the powder and the water with your fingers. After a few seconds, you will notice that the temperature of the hand warmer.
we found that so much heat was generated by them that some of the
plastic bags actually melted. If this happens when you try the experiment, drop the bags into a bucket of cold water and dispose of the resulting solution. Be sure to wash your hands in plenty of cold running water.
-no end-
posted by Arise! at 5:12 PM
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