When hiking, fishing, especially in bad weather, you often need an ordinary heating pad. Of course, an ordinary rubber one is not bad, but it has one significant drawback: The water is heated very slowly for her on the fire. Let's try to make a chemical heating pad. For this we need the most common reagents.

When hiking, fishing, especially in bad weather, you often need an ordinary heating pad. Of course, an ordinary rubber one is not bad, but it has one significant drawback: it heats up water very slowly over a fire.

Let's try to make a chemical heating pad. For this we need the most common reagents.

To begin with, let's conduct uncomplicated experience. Go to the kitchen and take a pack of table salt. However, you won't need a pack. 20 g (2 teaspoons) will be enough. Then look into the cabinet where all kinds of household supplies and materials are stored. Surely there was some copper sulfate left there after the apartment was renovated. You will need 40 g (3 teaspoons). Wood chips and a piece of aluminum wire, presumably, will also be found. If so, you're done. Grind the vitriol and salt in a mortar so that the size of the crystals does not exceed 1 mm (by eye, of course). Add 30 g (5 tablespoons) to the resulting mixture. sawdust and mix thoroughly. Bend a piece of wire into a spiral or snake and place it in a mayonnaise jar. Pour the prepared mixture there so that the filling level is 1-1.5 cm below the neck of the jar. The heating pad is in your hands. To activate it, just pour 50 ml (a quarter cup) of water into the jar. After 3-4 minutes, the temperature of the heating pad will rise to 50-60° C.

Where does the heat in the jar come from, and what role does each component play? Let's look at the reaction equation:

CuSO4+2NaCl Na2SO4+CuCl2

As a result of the interaction of copper sulfate with table salt, sodium sulfate and copper chloride are formed. It is she who interests us. If we calculate the heat balance of the reaction, it turns out that the formation of one gram molecule of copper chloride releases 4700 calories of heat. Plus the heat of dissolution in the initial resulting drugs - 24999 calories. Total: approximately 29,600 calories.

Immediately after formation, copper chloride interacts with aluminum wire:

2Al+3CuCl2 2AlCl3+3Cu

In this case, approximately 84,000 calories are released (also calculated per 1 g-mol of copper chloride).

As you can see, as a result of the process, the total amount of heat released exceeds 100,000 calories per gram-molecule of the substance. So there is no mistake or deception: the heating pad is real.

What about sawdust? Without taking any part in chemical reactions, they at the same time play a very important role. By greedily absorbing water, sawdust slows down the course of reactions and extends the operation of the heating pad over time. In addition, wood has a fairly low thermal conductivity: it seems to accumulate the generated heat and then constantly releases it. A tightly sealed container will retain heat for at least two hours.

One final note: a jar is, of course, not the best vessel for a heating pad. We only needed it for demonstration. So think about the shape and material for the tank in which to place the heating mixture.

Chemistry often works wonders. This time we present to your attention another homemade product, which is based on the chemistry and properties of some substances. We are talking about making a chemical heating pad, which in its properties is in no way inferior to a classic one.

You can watch the process of making a chemical heating pad by watching the author's video

What do we need:
- copper sulfate;
- spoon;
- food foil;
- kitchen salt;
- plastic bottle;
- wooden skewer for barbecue;
- glue gun.

Pour salt and vitriol into the bottle.

Add water.

In progress chemical reaction hydrogen and heat will be released, which will accelerate it. In this case, you need to constantly bleed off the hydrogen and monitor the pressure in the bottle by opening and closing the lid, as well as shaking it periodically.

Some time later aluminium foil will begin to dissolve, and copper will be released from the solution.

Gerasimenko Elena

The work “Thermochemical reactions in the creation of a chemical heating pad” examines practical use theoretical material about chemical reactions.

The choice of the problem of interest is justified. The ability to create a “chemical heating pad” at home from inexpensive scrap materials can be very useful in extreme natural conditions.

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Municipal secondary education state-financed organization average
secondary school No. 19 MO Korenovsky district

Scientific and practical conference for schoolchildren “Eureka”

"Thermochemical reactions in the creation
chemical heating pad"

Completed by a student of class 11 A of MOBU secondary school No. 19Municipal district Korenovsky district

Gerasimenko Elena Mikhailovna Head teacher of chemistry Bobrovskaya L.F.

Korenovsk

year 2014

annotation

The work “Thermochemical reactions in the creation of a chemical heating pad” examines the practical application of theoretical material about chemical reactions.

The choice of the problem of interest is justified. The ability to create a “chemical heating pad” at home from inexpensive scrap materials can be very useful in extreme natural conditions.

Availability analyzed Supplies. The thermal effects of reactions are calculated using standard enthalpies of formation of substances.

In her work, the student carried out experiments using new laboratory equipment Mishab, on the basis of which she calculated the ash effects of reactions and established the most effective reactions.

The result of the work was formulated recipes and recommendations for creating “chemical heating pads” in an understandable and accessible form.

The work has practical application and deserves attention.

Introduction.

In the cold season, people whose activities involve performing certain
tasks on the street, there is always a desire to warm up. But this is not always the case
conditions. The problem can be solved by using heating pads.

In my work, I decided to explore the problem of creating a chemical heating pad. The heating pad can be reusable. For reusable “warmers”, crystalline salt hydrates, which can be stored supercooled for a long time, are best suited. There are similar heating pads on sale, filled with crystalline sodium acetate hydrate SNZS0 (Zha-ZN20. This salt melts in its own water of crystallization at 58 ° C. The salt, placed in a plastic bag, is melted in boiling water and then the melt can be cooled to room temperature and below without crystallization ( hypothermia). Then it is enough to crumple the bag - and crystallization begins with the release of heat. This process can be repeated many times."

I was more interested in the possibility of creating a real chemical heating pad, which works due to exothermic reactions occurring in it. These heating pads are disposable, which is convenient because after use they can be thrown away or recycled.

I managed to find several recipes for such warmers. The goal of my work was to choose the most convenient, reliable, accessible, cheap and effective recipe, testing and testing it in practice.

. .) ^ > * 1 3

During my work, I studied the theory of thermochemical reactions, calculated the thermal effect of the selected reactions, and conducted experiments with the selection of different recipes.

Study plan

In the study of chemistry, we become familiar with thermochemical reactions that occur with the absorption or release of heat. Energy stored in substances in the form chemical bonds, is released during the formation of new substances. In chemical production, this energy is used to heat reagents or produce vapors or heat water.

The thermal effects of chemical reactions are necessary for many technical calculations.

The effect of certain exothermic reactions can be used to create a customized portable heater.

The goal of the work was to investigate some chemical reactions to create a thermochemical heating pad. For this purpose, some experiments were carried out using the most available reagents.

I want to explore the problem of using the energy of chemical reactions in miniature individual heating systems “hot water bottles”. For this it is necessary:

1. Study the issue and determine whether there are similar heating pads;
2. Select the most suitable reactions for creating chemical heating pads;
3. Select the most efficient reactions in terms of calorific value during a chemical comparative experiment;
4. Choose the most convenient form for filling and application.

1. Thermochemical reactions.

Thermochemistry -- a section of chemical thermodynamics, the task of which is to determine and study the thermal effects of reactions, as well as to establish their relationships with various physicochemical parameters. Another task of thermochemistry is to measure the heat capacities of substances and determine their heats of phase transitions.

Thermochemical equations

Thermochemical equations of reactions are equations in which near the symbols chemical compounds are indicated states of aggregation of these compounds or crystallographic modification and the numerical values ​​of thermal effects are indicated on the right side of the equation.

The most important quantity in thermochemistry is the standard heat of formation (standard enthalpy of formation). Standard heat (enthalpy) of formation complex substance is called the thermal effect (change in standard enthalpy) of the reaction of the formation of one mole of this substance from simple substances in standard condition. The standard enthalpy of formation of simple substances in this case is taken equal to zero.

In thermochemical equations, it is necessary to indicate the aggregative states of substances using letter indices, and the thermal effect of the reaction (TR) must be written separately, separated by a comma. For example, the thermochemical equation

4Ш 3 (g) + 30 2 (g) -+ 2Н 2 (g) + 6Н 2 0 (g), DN=-1531 kJ

shows that this chemical reaction is accompanied by the release of 1531 kJ of heat, at a pressure of 101 kPa, and refers to the number of moles of each substance that corresponds to the stoichiometric coefficient in the reaction equation.

In thermochemistry, equations are also used in which the thermal effect is related to one mole of the formed substance, using fractional coefficients if necessary.

Hess's law

Thermochemical calculations are based on Hess's law: The thermal effect (TE) of a chemical reaction (at constant P and T) depends on the nature and physical state of the starting substances and reaction products and does not depend on the path of its occurrence.

Corollaries from Hess's law:

1. The thermal effects of the forward and reverse reactions are equal in magnitude and opposite in sign.
2. The thermal effect of a chemical reaction (TR) is equal to the difference between the sum of the enthalpies of formation of the reaction products and the sum of the enthalpies of formation of the starting substances, taken into account the coefficients in the reaction equation (that is, multiplied by them)."

Hess's law can be written as the following mathematical expression:

∆ N in =∑(∆ N 0 reaction products) - ∑(∆ H 0 reagents)

Using data on standard enthalpies, I will calculate the thermal effect of reactions for chemical heating pads.

1. Recipes for chemical heating pads.

1. compound : One of the simplest chemical heating pads contains calcium oxide CaO ( quicklime), which reacts with water to form calcium hydroxide:

CaO + H 2 0 = Ca(OH) 2.

The reaction is accompanied by heat release. The temperature of the heating pad can reach 70-80°C.

1. compound : Another type of chemical heating pad uses the interaction of metals (in the form of shavings) and salts. A completely dry mixture of iron (Fe) shavings with copper salts (for example, CuCl 2 ) can be stored for quite a long time, and when water is added, the temperature immediately rises to almost 100°C due to the reaction:

F e + CuC1 2 = F eC1 2 + Cu.

At the same time, a heating pad in which copper chloride CuC1 2 turns into ferric chloride F еС1 2 , retains heat for about ten hours.

1. compound : Equipment: aluminum wire, copper sulfate, table salt, sawdust, water.

2A1 + ZSi S 0 4 - A1 2 (S 0 4 ) 3 + ZSi.

Sodium chloride is added to intensify the process; chlorine ions accelerate and facilitate the reaction with aluminum. Against the background of this reaction, there is probably also a reaction of aluminum with water, such as

2А1 + 4Н 2 0 => 2А10(0Н) + ЗН 2.

1. compound : To make a chemical heating pad, it is better to use copper chloride powder and aluminum filings. Mix 5-6 g of copper chloride with the same weight of aluminum sawdust and add 5-6 tablespoons of well-dried sawdust to the mixture. Pour the resulting mixture into a plastic bag. The heating pad begins to work when 30-40 ml of water is poured into the bag. Copper chloride, dissolving in water, reacts with aluminum:

ZSiS12+2A1=2A1S13+ZSi.

The reaction is accompanied by the release of heat. The sawdust acts as a "diluent" to prevent the reaction from proceeding too quickly.

1. compound : a mixture of potassium permanganate and iron powder in a steel cylinder. It was invented by the Japanese during World War II. Weighed about two hundred grams. As soon as you added a little water, this mixture began to warm up. The heating pad worked for up to 20-30 hours, and it outside temperature did not exceed sixty degrees, that is, it could not burn the skin. One such heating pad was enough to warm an adult.
2. compound : A flat polypropylene bag in which the oxidation of iron dust with atmospheric oxygen occurs, forming rust and generating heat. The mixture also includes water, salt (works as a catalyst), Activated carbon(distributes heat evenly), vermiculite (serves as a heat accumulator) and cellulose (filler). The heating pad is disposable, starts working after opening the sealed package (to ensure oxygen access) and is capable of providing heat for several hours.
3. compound : You can also add oxalic or citric acid(crystalline hydrates), which increases heat output. Such heating pads allow you to obtain temperatures from 100 to 300°C. To start them, a small amount of water is introduced into the reaction mixture of calcium oxide and oxalic acid crystal hydrate; during the reaction, the water released during neutralization will react with calcium oxide.

. - « ■ (IV /1 V*

CaO + H20 = Ca(OH)2 + 10.6 kcal

Ca(OH)2 + H2C204*2H20 = CaC204 + 4H20 + 31kcal

1. compound: MORE EFFECTIVE composition chemical heating pads are a mixture of iron filings, potassium permanganate, coal and sand. Coal and sand serve as reaction retardant fillers. Heat is released as a result of adding water to this mixture.

The resulting reaction when water is added to the mixture is:

4Ee + 2H20 + 302=2(Ee203»H20) + 390.4 kcal

Such a mixture, placed in a housing, allows you to maintain a temperature of 100°C for 10-12 hours. An individual heating pad of this type is a rubberized bag filled with the specified composition with a neck for pouring water.

1. compound: And the best disposable chemical heating pad (namely a chemical heating pad, since a reusable heating pad has nothing to do with chemistry) is a mixture of iron and copper filings with salt. It fills with water and starts to warm up.

CaO + H 2 0 = Ca(OH) 2

DN° 298 = DN° 2 98 (Ca(OH) 2 ) -(DN 0 2 98 (CaO) + DN 0 2 9 8 (H 2 O))= -985.1-(-635.1-285.83)= = -64.17 kJ/mol

Ee + CuC1 2 = HeC1 2 + Cu

DN° 298 = DN 0 2 98 (ReS1 2) - DN°29 8 (SiS1 2 ) = -341.7+205.85 =135.85 kJ/mol2A1 + ZSi804 = A12(80)3 + ZSi

DN° 298 = DN 0 298(A12(8O)3) - DN° 298 (Ci804)*3= -3441.8 -(3*(- 770.9))=-1129.12А1 + 4Н20 => 2АУ(ОН) + ЗН2 DN° 298 = DN°2 98 (A10(0N))*2 - DN° 298 (N20)*4 =

ZSiS12+2A1=2A1S13+ZSi.

DN° 298 = DN° 298 (A1S13)*2 - DN°298(SiS1 2 )*3-585,2 *2 - (-205,85 *3) = - 552,45

4. Experiment.

For determination of practical outputheat of different reactions, I will conduct an experiment. IN

under the same conditions I will observe the heatcreative ability of mixtures and cooling time.

Conclusion, the greatest heat output is observed when aluminum interacts with

copper chloride. Based on this mixture, the heating pad will work most effectively, but you need to select the proportions of the reagents

5.0 determination of the thermal effect of the reaction 5 grams of CuC were added to 50 g of water l 2 *2 N 0 and some aluminum powder. By

change in water temperature d e la thermal effect of reaction.

b. Recipe for a chemical heating pad

To create chemical greeks, you need to prepare a mixture.

For 1 tablespoon of copper sulfate, take 1 tablespoon of salt and add 1 teaspoon of aluminum powder. The temperature of the heating pad will rise to 100° and

gradually decrease.

Conclusion.

Thanks to the experiments carried out, it was concluded that the most optimal way to create a thermochemical heating pad is the reaction of replacing a metal from a salt with a stronger metal.

The main task practical work was to create a portable heater from available reagents, which would be used in the cold season and serve as a heating pad in camping conditions.

To create the heating pad, some reactions were carried out:

1. .Interaction of copper chloride (||) with aluminum

A mixture of copper chloride, coal and sawdust is prepared. I poured in aluminum powder. Added water. Using the device it was measured Maximum temperature heating (100°C) and time to lower the temperature to 22°C (approximately 1.5 -2 hours)

1. .Interaction of copper chloride (||) with iron

I prepared a mixture of copper chloride (dry), coal and sawdust. Added iron powder. Added water. Using the device, I found out that the substances interact poorly. The temperature rose from 25°C to 35°C, and lasted no more than 40 minutes.

1. Lime slaking

Calcium oxide was taken for the reaction. Added water. The reaction did not occur (most likely due to long-term storage, calcium oxide has turned into calcium carbonate).

Based on the experiments conducted, it was concluded that to create a heating pad, the most optimal reaction is the displacement of metal salts by a more active metal.

Experience has shown that many exothermic reactions occur aggressively, with violent gas release, with a small thermal effect and are not suitable for creating a thermochemical heating pad.

Bibliography:

FindPatent.RU2012-2013

You can and should fight the cold when you are in nature far from home. Moreover, there are now many modern and technologically advanced portable devices, individual heating pads, available for sale various types and types, compact gas heaters and so on, the operation of which is based on various physical and chemical processes.

According to statistics, from 10 to 15% of people who died in nature became victims. Even the warmest clothes, with negative temperatures air, can ensure the maintenance of positive heat balance the human body for only a very limited time. Sooner or later, heat loss will be greater than heat production and the body will begin to cool. Prolonged exposure to the cold is dangerous. It paralyzes the will and dulls the instinct of self-preservation. This could ultimately lead to at least serious problems with health, or at most - to death.

Disposable chemical heating pads and thermal bags for heating in field conditions.

The cheapest and available means Individual heating is provided by various disposable chemical heating pads (thermal packs) for hands and feet. The heat in such heating pads is usually generated as a result of a chemical reaction between the contents of the package itself and oxygen. Such heating pads are very easy to use; sometimes, to start the heat generation process, it will be enough to remove it from the package. The operating temperature, depending on the purpose of the disposable heating pad, is from plus 40 to 60 degrees Celsius. Operating time: 4 hours or more.

The design of some disposable chemical heating pads allows you to temporarily stop the process of heat release from it. To do this, it is enough to stop the access of oxygen to its active content and the reaction stops. Disposable chemical heating pads will be convenient autonomous heat sources for fishermen, tourists, hunters and military personnel. They can be put in shoes, in gloves, in the inner pockets of clothes, to warm up equipment (photo and video cameras) when working in the cold, etc.

Reusable salt warmers for heating in field conditions.

Reusable salt warmers are a sealed container made of dense material, which is filled with supersaturated saline solution. The operating principle is based on the effect of heat release when changing phase state materials. A salt heating pad can have almost any shape and size. For example, a salt foot warmer can be in the form of an insole.

Inside the heating pad there is an applicator (stick or circle), which is used to launch it. The operating temperature of salt heating pads is 50 degrees and above. The operating time depends on the size of the heating pad itself and the ambient temperature - from 2 hours or more. After the end of the work cycle, the salt warmers are brought into working condition by placing them in boiling water for a while, after which they are again ready for reuse.

Reusable catalytic heating pads for heating in field conditions.

In addition to disposable chemical heating pads, there are reusable pocket catalytic heating pads. The principle of their operation is based on the catalytic flameless oxidation of alcohol or gasoline vapor, which is accompanied by the release of heat. The catalyst in such heating pads is platinum. A striking example— classic pocket catalytic gasoline heating pad Zippo Hand Warmer. More details about it are written on our website.

Prevention of hypothermia in conditions cold weather.

In cold weather conditions, you should try to adhere to the following simple rules.

1. Generate heat.

Eat often, but little by little, and high-calorie foods. When food is taken frequently and in small portions, it increases the overall metabolic rate of the body, since more calories are spent on the digestion process. This in turn leads to the production of more internal heat.

If necessary.

- Do warming physical exercises.
— Light a fire and use reflective surfaces.
- If possible, always position yourself on the south side to receive solar heat to the maximum.
- Drink warm or hot liquids with sweets or sugar dissolved in them.

2. Reduce heat loss.

— Wear weather-appropriate clothing and shoes.
- Especially insulate the head and neck.
- As soon as possible, immediately change from wet clothes to dry ones.
- Find or make a protective shelter or shelter.
— Isolate the body from cold surfaces as much as possible.
- Quit alcohol completely.

On the Internet you can find many designs for homemade chemical heating pads for fishermen and tourists. The operation of the heating pad is based on a chemical reaction involving water, salt, aluminum and copper sulfate. A heating pad is used to warm numb fingers when fishing. You can use it to warm up cold food.
It must be admitted that the reagents are not cheap now, it may be easier and more profitable to take a catalytic heating pad, one refill is enough for 6-8 hours of operation, after 200-300 uses the platinum element is simply changed. But, according to the author of the development we are considering, the Chinese catalytic heating pad has its downsides. If you come across a weak one, the catalyst will last for a week. In addition, this heating pad is temperature sensitive. In the outer pocket the body cools down, the fuel stops evaporating and the heating pad without fuel stops producing heat. She is capricious in this regard. Even the case doesn't help. And if you take it with frozen hands, it will cool down very quickly.

The author of the video tutorial first demonstrates the mechanism of operation of a chemical heating pad. To do this, he took copper sulfate bought in a store and ground it in a coffee grinder. However, he had to grind the vitriol only to demonstrate the operation of the device, since large crystals crack when heated. Copper sulfate calcined in order to increase the initial temperature of the solution, so as not to wait a few extra minutes before the reaction begins, but you can do without it.

What aluminum is used in the heating pad? Food foil. Width 28 cm, length 20 cm, thickness 14 microns. The ratio of copper sulfate and kitchen salt is 2:1. A bamboo skewer is glued into the cork using hot glue.

In the experiment it is very cold water. The mixture is heated to room temperature by dissolving anhydrous copper sulfate. Shake the bottle with the mixture to speed up the chemical reaction. The foil on the skewer will heat the liquid in the bottle evenly. During the reaction, hydrogen and heat will be released, which will speed up the reaction. The pressure in the bottle must be monitored and the hydrogen must be constantly released. Aluminum dissolves and copper is released from the solution. If no gas is released within a minute, the reaction is over. In principle, you can even boil water, but the bottle will not withstand such heat.

And now about how not to make a chemical heating pad.

Wanting to reduce reaction time to a minimum, the author of the video decided to increase the aluminum contact area. For this purpose, he crushed aluminum plates. Next, as usual, I put salt and copper sulfate in the bottle in the required proportions. Filled it with water. Stirred. I threw in the aluminum blank and screwed on the lid. Having opened the lid slightly to vent the hydrogen, he received a charge of dirty hot liquid on himself.

Watch the video experiment showing the chemical reaction behind the heating pad and how to make one yourself. Well, if you want to see immediately “what the violation of technology resulted in,” that is, about the dangers of chemical heating pads, then from the moment 3:41.

Features of the heating pad made from copper sulfate proposed by the author.

A similar recipe has been floating around the internet for decades, but it all boils down to mixing salts, adding sawdust, aluminum and water. And yet not
it is clear how to regulate the reaction speed, the temperature of the heating pad and how to remove the released gases. The author chose a simple path. A short but active chemical reaction produces heat that holds the salt mixture. This allows you to save reagents and keep the temperature in a comfortable range.
As the heating pad cools, you can add new portions of aluminum.

The rate of a chemical reaction depends on the concentration, temperature, and surface area of ​​the reactants. Therefore, aluminum is in the form of foil, and not wire, pipes, corners and other things. Because The concentration of salts decreases during the reaction, then there should be an excess of salts. The solubility of copper sulfate in 100 grams of water at 25 degrees Celsius is 23 grams. I don’t recommend taking more than 4 times the amount because... During the reaction, copper is released in the form of a fine powder, which thickens the salt solution and prevents the circulation of the solution. Copper sulfate was calcined in order to increase the initial temperature of the solution, so as not to wait a few extra minutes before the reaction began, but you can do without this.

The wooden skewer is designed to sink the foil bundle and isolate it from the walls of the bottle. Otherwise, the foil becomes covered with many bubbles and floats. In this case, all the heat is released in the upper part of the bottle, which leads to strong heating and deformation of the walls. In the case of a skewer, gas bubbles cause the liquid to circulate, so it is not necessary to constantly shake the bottle and release gas. It’s enough just to let the bottle sit for a couple of minutes without tightening the cap. The army works on the same principle.
flameless food heaters.

The other is a safe heating pad with a very interesting operating principle.