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Останнє оновлення:
27.03.2017


Case lesson "Fire - the fourth element"
Case lesson "Fire - the fourth element"

Section: Science, Nature and Man

The level (grade): 8 +

Subject: Natural phenomenon

Objective: To expand and systematize knowledge about fire, its scientific, technological, cultural, historical and philosophical significance

What information is waiting for me here?

  • What is the fire and what is burning?
  • What does produce the blue flame?
  • How does water burn?
  • How to ‘burn’ stars?
  • What fundamental and practical knowledge will be useful to me?
  • When does the fire help to create, but whendoes it become a destroyer, and how to avoid it?
6 scans of the subjects, phenomena and practices:
Introduction

What is fire? One of the four elements that according to ancient beliefs creates the diversity of our world (fire, water, earth and air).

How does it occur and what happen? How to "tame" it? People worshiped fire in ancient times. The fire turned human history; it was the turning point in the development of human civilization.

It became a central figure in philosophy, religion and people perceptions about the structure of the world. Fire launched the development of technology and gave humanity way from the alchemist to rocket science.

 

The fire may ignite and burn, highlight and repay, give warmth and pick it up (cold fire).

The fire has the strength and power that we learn to understand, opening more and more opportunities and avoiding negative consequences.

Chemistry

Flames are the visible manifestation of combustion.

But what is burning? At first glance, it is oxidation reaction (because burning is impossible without oxygen!). But breathing and rusting metal - is also oxidation!

And during the breathing we "breathe" heat.

Maybe it's also burning, but some slower? Find the answers to these questions!

Consequently, chemists say that the burning is oxidation that occurs with a fairly high speed and accompanied by heat and light:

 

Terms of burning:

• flammable substance,

• oxidant (oxygen),

• heating combustible material to ignition temperature:

Each substance has its ‘combustion’ temperature. For example, the air can be ignited from hot wire, and to ignite wood, it should be heated to several hundred degrees.

The most important for combustion condition is the presence of oxygen:

 

Many other processes also generate heat: rotting leaves, metal oxidation (rusting), aerobic breathing of creatures.

But this generating is slow because of the duration. But if a piece of wood burn rapidly or undergo a slow oxidation in air for years, anyway - in both cases it will release the same amount of heat. Thus, the difference between burning and slow oxidation is:

 

Any chemical reaction is accompanied by the release or absorption of energy. Most energy is released or absorbed as heat (at least - in the form of light or mechanical energy).

This heat can be measured. The result of measurement expressed in kilojoules (kJ) for one mole of moles reactant or reaction product. The amount of heat released or absorbed during a chemical reaction called the heat of reaction (Q).

For example, the heat of reaction of hydrogen combustion in oxygen can be expressed in any of the two equations:

2 H2(g) + O2(g) = 2 H2О(I) + 572 kJ

2 H2(g) + O2(g) = 2 H2О(I) + Q

This equation is called thermochemical reaction. Symbols «+ Q» means that the combustion of hydrogen released heat. In thermochemical equations often point aggregate state of matter. Reactions that occur with the release of energy are called exothermic (from the Latin "exo" - outside). For example, the burning of methane:

 

When the reaction proceeds with the absorption of energy, it is called endothermic (from the Latin "endo" - inside). For example, the formation of carbon monoxide (II) CO and hydrogen H2 from coal and water, that occurs only during heating:

 

Thermal effects of chemical reactions are necessary for many engineering calculations. For example, for rocket engines. If you know the energy (in kJ) you have to spend to deliver rockets with cargo from the Earth to orbit and other energy expenditure during flight, how to calculate the required supply of hydrogen and oxygen, which (in LP mode) are used in this rocket as fuel and oxidizer?

It is difficult to do it without the help of the heat reaction of water formation from hydrogen and oxygen. Thermal effect - is the same energy that must launch rocket into orbit. In combustion chambers of rocket this heat is converted into kinetic energy of the molecules of hot gas (steam), who escapes from nozzle creates jet thrust.

What is the color of light? Free radicals and molecules in excited states can occur in the area of combustion. If the glow intensity is high enough, it can be perceived with the naked eye. Flame color is determined by the frequency where radiation is in the visible spectrum.

Much of the radiation, especially if there are the dust particles or soot particles in the flame, is in infrared part. It is seen by man as the heat from the fire. By adjusting the air flow (eg a special Bunsen burner, which burns propane) the color of the flame can also be changed:

 

1 - air supply in the burner is closed; 2 - supply of air from below almost is blocked; 3 - close to stoichiometric mixture (calculated based on the equation of the combustion); 4 - max air supply.

But has a fire been that color all times? Does the phrase "mountain it blue flame" have real reflection? Yes! Depending on the substance burns, burning range varies, and therefore changes the color of flame:

Liquids also can burn, such as oil, alcohol. But can "make” water to burn? It is possible!

Task:


Spend a mini-study on one of the themes and prepare a little message as the results:

• Which substances have the highest temperature combustion?

• What substances are burning with an unusual color?

Do not forget to bring appropriate chemical reactions!

Physics

First of all, the process of burning is thermodynamic process. So it is described by thermodynamic equation:

 

Although that it is said "there is no smoke without fire", but there is burning without fire! Unlike conventional combustion when there is a flame zone that glows, it is possible conditions for flameless combustion.

An example is the catalytic oxidation of organic compounds on the surface of the catalyst, such as ethanol oxidation on platinum mob. However, the term "flameless combustion" is not limited to the case of surface-catalytic oxidation, and indicates situations in which the flame is not visible to the naked eye (but it is!).

Sometimes the combustion process visually looks like a blizzard of sparks. For example, burning ammonia in the presence of chromium oxide:

Incandescent particles of chromium oxide (III) accelerate the reaction of ammonia oxidation by atmospheric oxygen. On the surface of chromium oxide particles is exothermic oxidation of ammonia. It is formed sheaf of sparks that are circling inside the vessel as snowflakes in a blizzard. These catalyst particles - chromium oxide (III), where there is the oxidation of ammonia. The oxidation of ammonia to oxygen is to nitric oxide (II).

How does fire burn in zero gravity?

Despite the fact that the fire experiment on the space station is very dangerous, 80 candles were burned in 1996 on the ISS "World".

It turned out that candle that burns completely on the Earth for 10 min, can be burned on the station during 45 minutes. But the flame was too weak and bluish, it could not even videoed and to prove the existence of the blaze, people had to bring to it a piece of wax and shoot as it melts:

The process of burning in zero gravity can be maintained only by molecular diffusion or artificial. Without ventilation heat radiation cell burning only cools it and eventually can stop the process, leaving even smoke. So to stop the fire in zero gravity it is enough to perform ventilation and wait a bit.

In weightlessness flame is smaller as usual and not as hot as ever, since there is not enough fresh air containing oxygen. Therefore, there is only little soot, because it is formed at a temperature below 1000 ° C. But even if it was enough, and then because of the low temperatures it would shine in the infrared range, and therefore color the flame in weightlessness is always bluish:

But because there is no upward movement of air in weightlessness, the flame has spherical shape. For the same reason, lit candle in weightlessness almost do not have smoke.

In the space boats demonstrated that balls of burning gas mixture allocate so little power (<1W), which is burning each of them can be several hours.

Fire in technology, in everyday life, in space ... what does allow fakir to "breathe" fire? Actually, "how the dragon works?" After the legends dragons had ability to breathe fire, and a circus attraction "exhaling fire like a dragon» (fire breathing) comes from India.

This attraction, according to its performers, doesn’t require special skills, but is considered the most dangerous attraction associated with fire. Not only because of the obvious danger of burns:

To make the stunt safer fire fakirs used those substances that have a high ignition temperature (flash point, FP) mixed with air. For safe tricks needed to FP was above 50 ° C.

This option is very important as it shows where temperatures can continue burning mixture, if the source of fire (torch) removed. For example, for gasoline FP = 43 ° C, diesel FP = 62 ° C, kerosene FP = 38-72 ° C, and for liquid paraffin FP = 90 ° C. Therefore, fakirs often use liquid paraffin, and they are not be afraid of uncontrolled explosion of combustible mixture.

Flame color depends not only on the material that is burning, but on the temperature of combustion. If you pay attention, flame or fire has match uniform in color. It has several colored zones with different temperatures:

 

Task:


Watching the fire (fireplaces, furnaces, fire, candle, torch, matches, etc.), determine what color have the flames and make a conclusion about its temperature. Form table of its observations:

 

 

Compare your observations in the classroom and make a general conclusion.

Astronomy / Cosmology

Stars are a huge fiery ball of gas. And they are fire, the color of stars can say about the temperature of combustion. The coolest stars will be red and hot stars blue.

What determines the temperature of stars? In fact, it all comes down to its masses:

Dependence color dawn of its temperature

There are many stars. There are the most unusual among them.

Or:

The most common stars in the Universe are the relatively tiny red dwarf stars. These stars can have as little as 7.5% the mass of the Sun, and top out at about 50%. Red dwarfs use their stores of hydrogen fuel very slowly; it’s believed that a red dwarf star with about 10% the mass of the Sun may live for 10 trillion years or more.

Chemical and physical transformations occur in stars over millions years! This is combustion process, stretched to incredible intervals, but it is thermonuclear burning.

The star begins its life as a cold sparse interstellar gas cloud. Gradually it is compressed under its own gravity and takes the form of balls.

During the compression gravity energy is converted into heat and the temperature of the object increases. When the temperature in the center reaches 15-20 million K (Kelvin), thermonuclear reactions begin and compression stops. The object becomes a star:

 

The first stage of stars life likes the sun - it is dominated by the reaction of hydrogen. In this state, it is a big part of its life until it "fuel supplies" runs in its nucleus. When all the hydrogen is converted to helium in the center of the star, helium nucleus is formed, and continues thermonuclear burning of hydrogen in the periphery of the nucleus.

What, then, are solar flares? This is explosive process of energy release (light, heat and kinetic) in the solar atmosphere. Flashes cover all layers of the solar atmosphere:

Energy releasing a powerful solar flare could reach 160 billion megatons of TNT, which, by comparison, is estimated volume of global electricity consumption by 1 million years.

History / Philosophy / Technology

Meeting man with fire marked the beginning of religious beliefs, philosophical concepts and technologies. Let us consider how these trends have evolved. In Paleolithic man began to use fire and protect it as one of the most important values:

 

There was further development of religious ideas associated with fire, and technology improvements in the Neolithic. One of the most common ways to get fire - friction:

 

In ancient Egypt Fire "gets" own goddess - Sekhmet, the goddess of cosmic fire. In philosophical and religious concepts of that period fire was associated with vivifying force mother home. This approach was very common, and the use of fire as a religious practice was very often. Fire was also the object of worship and symbol, and way of sacrifice:

 

Ancient times were marked not only a new approach to technology use of fire, but also to religious values and religious fire. The fire was perceived as one of the elements, entities, lying on Greek ideas at the heart of the world. It was also "a military ally." For example, look at "grenades" with Greek fire:

 

Elements were presented as universal qualities. Relations between the two phenomena explain the diversity of the world. Therefore, the theory of the four elements (earth, water, air and fire) was the theoretical basis for further alchemy and one of the foundations of Western astrology.

In Greek and Roman mythology, several deities (Hephaestus, Prometheus, Vesta, Hestia, etc.) were identified with the fire. In ancient Indian mythology Agni was the personification of fire, in Celtic mythology Brihid was the goddess of fire.

The splendor of fire has been throughout history the central symbol of Zoroastrianism. According to traditional views Zoroastrian, fire pervades the whole being both spiritual and physical. For Zoroastrianism it is typical to select some Fire incarnation:

• Highly saving - one that burns before Ahura Mazda in paradise.

• Good friendly - one that burns in the bodies of humans and animals.

• Pleasant - one that burns in plants.

• Efficiently - fire lightning.

• Holy - ordinary earthly flame, including fire Varahram (Victorious), the churches burning.

 

The technology the use of fire also improved, for example, for the production of weapons. Japanese katana that period was considered one of the most accomplished kinds of knives, "born of fire":

In the Middle Ages technological importance of fire has significantly increased. And not only through metalwork. Glass, ceramics, salt, perfumery, manufacture of medicines, dyes, alchemy were simply impossible without it. New alloys and materials have expanded the opportunities for other items:

At Christianity that period fire was ambiguous: on the one hand, it was the personification of hellfire, but on the other - Easter Holy Fire:

In medieval alchemy and mysticism in the element of fire were their spirits that lived in it - salamanders:

 

From medieval alchemical experiments chemistry appeared that would be impossible without the use of heat, evaporation, rectification, ashing and many other processes that formed the basis of modern chemical synthesis and high-tech industries have grown in our days.

But how was the fire fueled at that time? Before the invention of matches the fire was fueled using flint:

More unusual way - to fuel the fire with the help of sunlight:

This method is possible only with adequate treatment of glass or other materials that focus light. Experiments show that the quality of the lens can be used even there is decorated ice! These videos are online.

Modern metallurgy is successor to forge fire. But the processes used in modern industry, are more difficult and impossible without the current level of "ownership" of fire:

Task:


Take a mini-project "Fire in the modern world." Select one of the directions of fire use in industry nowadays and describe it. You can prepare a small presentation about it. In preparation must note what properties of fire, since you've already learned, are applied.

Art

Fire can be a "canvas", a "brush" and "model" for modern artists.

Fire instead of patterns and palettes. For example, Adil Kusiv creates stunning photographs of fire. He pours flammable liquid on the table, ignites it and waits for a good shot. The author of fiery pictures says that not everyone can see cats, dogs, people in his photographs. Do you see?

 

 

Fire instead of brushes is art foundation of wood burning:

Fire-shows are popular in today's world, the descendants of ancient fakirs and fire jugglers. It is kind of street performance, much of which is to perform tricks with fire and use fire to the creative planning, ideas. Fire show is usually performed by a group of several artists and is traditionally called Fire theater:

In your opinion, what the technique was used to paint this picture?

 

It was used a special program to create it – «fire drawing»: flamepainter.ru

You can also try to create your masterpiece.

Fire may become a tool for hairdressing:

According to a theory this procedure not only looks impressive, adds uniqueness to hair, but it is beneficial to the hair.

Safety / Health

Fire is not only beauty, philosophy, science and technology as "one element". It is fraught with potential danger that non-compliance with the rules can become very real and devastating.

Basic safety rules:

 

If a fire does happen, the main thing you should do - do not panic! Then follow these rules:

 

What is used to extinguish the fire?

Water is considered the most common tool in the fire. It is able to cool the burning object, and reduce the temperature of the fire. If you fill the place of fire above, water fire knocks from the surface of the object, and flowing down, it does not flare up again and spread to other sites.

Water conducts electricity, so it is not recommended to fill objects that are connected to the network. There is a risk of a short circuit. Therefore, if the electric lights object burns, you first need to disconnect the plug and disconnect the general switch in the house. Only then can use water, sand and fire extinguisher.

You also can not fill with water flammable liquids, such as gasoline and kerosene, especially if there is an outbreak in the room. Such fluid is much lighter than water, so they just float to the surface and burn on. The area of the outbreak may increase as the water will spread on the surface.

It should be used sand, earth and fire extinguisher to extinguish flammable liquids.

You can also get rid of the fire using blankets, coats and thick cloth soaked in water before that.

Compliance with the rules. No matter how trite it may sound, it is a guarantee that the fire will only heat source and inspiration, not destruction and misery.

Interactive methods
"Combustible, non-combustible"

The essence of the game: The children are in a circle, or occupy space in the room so that you can throw and catch the ball. The principle of the game is built the same way as for the famous game "edible-inedible." Leader calls some stuff, but the one whom he throws the ball, should tipped the ball, if the substance is incombustible or catch if the substance is flammable. Teachers should focus on topics of material chemistry course dedicated to processes of oxidation and combustion.

OBJECTIVE: Active breathing, mobilization, training of concentration, attention, coordination, while fixing material curriculum.
Lesson summary:

Name

Зміст

1

A result of Case Knowledge Hypermarket can add the following findings of students:

 

2

What 3 sites helped to get information?

http://edufuture.biz/

https://sites.google.com/site/himulacom/zvonok-na-urok/8-klass/urok-no23-gorenie-i-medlennoe-okislenie-teplovoj-effekt-himiceskih-reakcij

https://ru.wikipedia.org/wiki/%D0%93%D0%BE%D1%80%D0%B5%D0%BD%D0%B8%D0%B5

 

3

To help the student and coach:

http://edufuture.biz/

https://ru.wikipedia.org/wiki/%D0%9E%D1%81%D0%B2%D0%BE%D0%B5%D0%BD%D0%B8%D0%B5_%D0%BE%D0%B3%D0%BD%D1%8F_%D0%B4%D1%80%D0%B5%D0%B2%D0%BD%D0%B8%D0%BC%D0%B8_%D0%BB%D1%8E%D0%B4%D1%8C%D0%BC%D0%B8

https://ru.wikipedia.org/wiki/%D0%97%D0%BE%D1%80%D0%BE%D0%B0%D1%81%D1%82%D1%80%D0%B8%D0%B7%D0%BC

http://bezopasnost-detej.ru/spravochnik-zashchita-detej/30-p/40-pozhar-pravila-povedeniya-detej

 

4

Where to take information for the Case:

http://edufuture.biz/

https://sites.google.com/site/himulacom/zvonok-na-urok/8-klass/urok-no23-gorenie-i-medlennoe-okislenie-teplovoj-effekt-himiceskih-reakcij

http://fas.su/page-508

https://ru.wikipedia.org/wiki/%D0%93%D0%BE%D1%80%D0%B5%D0%BD%D0%B8%D0%B5

http://pikabu.ru/story/plamya_v_nevesomosti_2019575

http://fizika-vnutri-nas.narod.ru/mol_physics/fire.html

http://v-kosmose.com/zvezdyi-vselennoi/temperatura/

https://ru.wikipedia.org/wiki/%D0%A1%D0%BE%D0%BB%D0%BD%D0%B5%D1%87%D0%BD%D0%B0%D1%8F_%D0%B2%D1%81%D0%BF%D1%8B%D1%88%D0%BA%D0%B0

https://ru.wikipedia.org/wiki/%D0%9E%D0%B3%D0%BE%D0%BD%D1%8C

https://ru.wikipedia.org/wiki/%D0%9E%D1%81%D0%B2%D0%BE%D0%B5%D0%BD%D0%B8%D0%B5_%D0%BE%D0%B3%D0%BD%D1%8F_%D0%B4%D1%80%D0%B5%D0%B2%D0%BD%D0%B8%D0%BC%D0%B8_%D0%BB%D1%8E%D0%B4%D1%8C%D0%BC%D0%B8

https://ru.wikipedia.org/wiki/%D0%97%D0%BE%D1%80%D0%BE%D0%B0%D1%81%D1%82%D1%80%D0%B8%D0%B7%D0%BC

http://bezopasnost-detej.ru/spravochnik-zashchita-detej/30-p/40-pozhar-pravila-povedeniya-detej

5

Locations of the lesson:

Case lesson takes place in the classroom. Carrying classes at the museum, park, library...

6

Race:

Teams of boys and girls.

The score of the competition between teams was…

Targets for them:

1. Try to play game "Fuel - non-flammable" on the basis of the game "edible - inedible." Each correct answer - 1 point. The winner team - leader in points.

2. With what the physical and chemical phenomena is fire associated? The winner is the team that gives more correct answers.

3. Offer an icon - the image of fire. Every team will present and defend its project.

7

Hometask:

Try to fantasize "What would happen to our world if people have not learned to use fire?" The results can be presented in the form of stories, work, reflection, pictures and presentations.

8

Duration of Case

90 minutes(double lesson).  

9

Ability to circuit classes with student-double for:  

possible

10

The results produced and competence:

 Understanding the relationship of chemical and physical processes associated with fire.

The ability to find, organize and analyze the received information quickly.

Ability to critically interpret and compare the information, establish causal relationships on the example of the historical processes of fire development by mankind.

11

Теги:

Burning, oxidizer, ignition temperature, the amount of heat, the heat of reaction, evolution of stars, alchemy, elements, metallurgy, fire. 

12

Tags:

Grabowska Larissa L.

13

Took part in case apgrade:

 

The End

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