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Case-lesson «Window to the World»
Case-lesson «Window to the World»

Category:Science, nature and man

The level (grade): 8+

Subject: Applied science

Objective: Learn about modern technology in such ordinary objects as window

What information is waiting for me here?

  • How can the windows help to keep warm?
  • Why the portholes are round?
  • Can the window be considered as an optical device?
  • What windows are the most durable?
  • What fundamental and practical knowledge will be useful for me?
  • What were the old windows?
  • How can you calculate the cost of the window?
6 scans of the subjects, phenomena and practices:

Window. For some people this word is synonymous with architectural delights, for someone – with lovely stained glass. For someone windows are primarily information technology Windows. For those who are thinking about energy saving window is a source of keeping warm. For engineers windows are an incentive to look for unusual technical solutions. And someone does not think anything but just enjoying the beautiful view from the window or rain drops on a window pane.


So, what are the scientific secrets and mysteries "can be seen from our window"?


The windows of our houses are not only a source of "visual information" and lighting. It plays very important role in the processes of ventilation and heat conservation inside. By what principle and with what physical laws do they retain heat?


Heat transfers through the window according to the law of internal energy conservation. Heat exchange begins if we consider a system consisting of two bodies with different temperature. In this process a heated body will give off heat (thermal energy), and cooler body will get it. But the total internal energy of these bodies must be maintained. Therefore, if internal energy of one body decreases, the internal energy of another body increases.

It can be used with thermal energy: the amount of heat given to the heated body is equal to the amount of heat obtained by the cold body (of course, it will be the value of the "modulo").


It is called the equation of thermal balance. Body internal energy is proportional to the mass and temperature of the body, and it is:


Specific heat indicates how much warm is required to heat 1 kg of substance by 1 degree. For window glass specific heat is 840 joules, and for air this value is not constant– it dependents on pressure, temperature and humidity:


Therefore, the task of the window is to keep warm in the winter and take away "extra" heat in the summer, that is – to minimize the heat transfer process.Otherwise in the winter the air in a heated room will give warm (the window and the air outside the window), at the same time being cooled. And in summer, conversely, it warms up, "taking" heat from the stuffy streets.


Consider, for example, how much heat is able to "accept" our window, if it is frost outside -5 , but inside is 18 (Celsius)?

Let's take an ordinary window glass of thickness 4 mm. Mass can be calculated based on the reference data:


If a size of the window is 1.0 m by 1.5 m, then the area will be 1.5 sq. m. Then the weight will be 10*1,5 = 15 kg, respectively. Considering thermal conductivity and temperature difference, we obtain:


This is comparable to the heat required for boiling of 0.9 liters of water (when the water heat capacity is 4.200 J/kg): 4200*0,9* (100 - 25) = 283.500 J = 283,5 kJ.

But is it possible just to write the equation of the heat balance for the window and use it to explain and calculate these two processes: protection against cooling in winter and heat in summer? No, because the window with the outer and inner air is much more complex system than two bodies with different temperature. Moreover, if we are talking about modern windows with different glazing units filling or special coating.


So, for windows we use the coefficient of thermal conductivity (K) and thermal resistance R0. The thermal conductivity characterizes the amount of heat in watts (W) that passes through 1 square meter of window (or other structure) when the temperature is different to 1 degree on either side of the window (often the Kelvin scale K is used). The unit of measurement is W/m*K. The smaller the value is – the less heat transfers through the window, so heat-insulating properties are higher. The value of heat transfer resistance characterizes it. But direct mutual conversion of these quantities is impossible because of peculiarities of measurement parameters. Certified windows are labeled by two indicators. The average resistance for different types of windows is:

Single glazing – 0,18 W/q.m*K

Double glazing – 0,39 – 0,42 W/q.m*K

Triple glazing – 0,55 W/q.m*K

That is why argon is used between frames as a substance with high thermal resistance and low thermal conductivity. It is like a kind of insulating material.


Look at the windows at your home: what material, how many layers of this material were used? What is its role in energy conservation at your home?


Our windows are rectangular. But the portholes of submarines, space ships and airplanes are round (oval) shape. Why?


The round shape is due to the fact that it weakens construction. A square window has four 90-degree angles, so it has four weaknesses. Under pressure (namely, portholes are used in such circumstances) the impact on corners and cracks go in these places. When it is round the pressure is distributed evenly over the entire surface. And from the point of technology view such portholes are better – easier to manufacture and install.

In contrast to the theoretical strength, the real strength of the glass is not physically reasonable parameter. It depends on the chemical composition and production technology of glass, technology of samples manufacturing and their sizes, physic-chemical properties of the environment and test temperature, speed and duration of loading.

Modern planes have a small hole in the glass portholes. At first glance it is through, but it is not so. The hole is made only in the inner glass.


The porthole is an original glass where the outer glass is stronger than the internal because it is affected by pressure and the inner protects from thermal effects. The hole in the inner glass allows equalizing the pressure, "sucking" or, conversely, pushing air from the space between glass panes.

What are the portholes used on space shuttles and stations? Because the conditions of operation are the most stringent among total number of portholes.

The porthole of a spaceship is a constructive element as well as an optical device at the same time.


Glass breaks differently than other materials. First, there is a microscopic crack followed by destruction of all glass. Therefore, it is important to protect the glass from micro meteoric flows. For this, the glass space ships are polished more carefully than the lenses of optical instruments to strengthen the surface as much as it is possible. Moreover, the portholes are a part of the optical spacecraft hardware.


Portholes are protected with a special coating (oxide of tin or indium applied by means of cathode sputtering) to increase the glass light transmission. This is very important for portholes manufacturing. For example, when a spacecraft flied to a comet, inside of it two cores have been found. It was recognized as an important scientific discovery. But when apparatus returned it was found that the second core "appeared" due to the fogging of the window that led to the optical effect of the prism.

Gradually the traditional glass will be replaced by other more sustainable material: acrylic plastic. This is necessary not only from the standpoint of optical effects and pressure, but also from the point of view of temperature effects. Thermal wear can happen when apparatus enters in the atmosphere.

For example, acrylic plastic was used for portholes of the spacecraft Orion, designed to deliver cargo and astronauts into orbit.


So, in the future windows will be with a special coating or polymeric materials (e.g. acrylic-based). These windows are designed to be multifunctional: protection, optical device and the light source.


During the history "evolution" of windows went in two directions: on the one hand we can study the evolution of forms, size, and decor, on the other – materials used for manufacture.

Kind of traditional window formed in Antiquity. Most often windows were square or rectangular with different decor. Over time windows were transformed into windows with semi-circular top. Semi-circular or round windows were used much less frequently. The main goal was additional lighting.


Windows of the Romanesque style became "heirs" of all the styles that had been before: windows of Rome, windows of Greek, windows of buildings of the Ancient East. Therefore, there were a lot of shapes: rectangular, arched, and even similar to two neighboring arches. The size of windows was changed and it was small. Why? Vaulted roofs replaced flat roofs; load of bearing walls was increased. Therefore, in order not to weaken the wall people began to use small windows. In addition, these windows could be easily changed from the source of light to loopholes. For that outer side of the window was more internal.


Romanesque style was replaced by Gothic. High lancet windows and roses (round windows) became independent works of art. Very often windows of cathedrals, churches and palaces were made of stained glass:


The splendor of Baroque was replaced by Gothic grandeur. Windows were change, too: windows of various forms were used, but almost always they were made with small hinged articulations. They were richly decorated and used for lighting and decoration of the facade.


The windows of the period "Classicism" were dainty and symmetrical. Most often they were separated by casements. These windows had been dominating in the architecture during nearly 100 years (XIX century).


The windows of XX century are diverse in form and decoration. At this time a whole galaxy of styles has come: modernism, art Nouveau, art Deco, constructivism, and many others.


Modernity is not far behind in the variety of window styles, because now almost all the historic types of windows are used with adding of a few modern directions. For example, the direction of biotech. Basic idea is expression through using natural forms.


About the evolution of materials: it passed beginning from the bullish bubble to modern plastic and glass with a special coating.


Modern windows like an echo of the Romanesque style can also be stained:


Sometimes we hear unusual names of windows: blind window, French window, Venetian window, dormer window, and attic window. What types of windows we are talking about?


Modern architecture allows using different types of windows, and only skills and imagination of architects and designers will show whether they are still functional.


What windows would you like to see in house of the future?


Human psychology gives ground for illusions. Especially if people are accustomed to the stereotypes: water is wet, a tree is solid, and a window is rectangular...

Look closely, what is a form of this window?

This window is trapezoidal! There is a secret of illusion:

Device for demonstration of this illusion consists of the trapezoidal surface shape. On both sides of this form the window openings and the shadows were drawn in such a way that observer thinks that it is rectangular window turned at a slight angle!

In fact, the window has a trapezoid shape. We are so used to rectangular windows that this window seems rectangular but rotated at some angle (if there are not enough indications of depth and distance, which would indicate that it is actually not tilted and rotated).

Trapezoidal window is mounted on the vertical rod and rotated by a small motor (speed of rotation — from 3 to 6 turns per minute). If you look at the rotating window with one eye from a distance of approximately 3 m, or with two eyes from a distance of 6 m or more, it seems like the window (turning 180°) immediately stops and reverses the direction of rotation. It sways along the axis of the rod. So, it is not seen as a revolving trapeze but as swinging rectangle, changing direction of rotation every 180°.


The window is a modern information technology, too. How does it work? The gist of it is that a rectangular sector of the window is given for each program on the screen. Window is an element that became the foundation of the Windows operating system. User does all operation in this program. When using multiple windows, information or other objects are constantly moving between them.

Windows are user-visible objects (and a part of invisible, too). Application windows are top-level windows. Windows that open in-app are subordinates. Parent window (a window from which they were invoked) is identified for each of them.

For example, the window to insert the SmartArt element and the parent window is the Word.


Each window has a size and coordinates. The coordinates can vary: for parent windows relative to the top-left corner of the screen, for subordinated – relative to the top left corner of the parent window. There are messages to interact between windows. Every event (mouse click, for example) causes sending a message to the appropriate window. The program for this operating system consists of these messages processing. Each type of window has own class – specific set of data and functions.


All modern houses are built with new windows. In old houses, where it is possible, people try to replace old windows with new energy saving windows. It is important to take into account the architectural appearance of building as well as historical and architectural value of old windows.

What is the price of new energy-efficient windows?


Installation of energy efficient windows is not only expensive but also the possibility to save heat and, accordingly, money on heating a room. It is very important to choose the right design and type of the window to balance "light-energy-efficiency-price".

Lesson summary:




The results of the lesson-case can be complemented by  findings of students



What three websites helped to find important information?







To help the student and the coach:







Where can you get information for the case?











Location of the lesson:

Кейс - урок проходит в классе. Возможно проведение в музее, библиотеке.



Teams of boys and girls.

The score was:....


1.What materials are used for modern windows manufacturing?

2. Calculate the amount of heat that a glass is able to take (thickness of 5 mm and a size of 1.7 square meters) when it heats at 5 degrees? 



 Сформулировать по пять вопросов к материалу кейса (индивидуальное задание).



90 мин (спаренный урок)



The possibility to conduct the lesson with a student-understudy 



The acquired knowledge and developed competence:

 Знание о физических закономерностях, лежащих в основе энергосберегающих технологий.

Знание о технологических особенностях современных окон.

Получение практических навыков применения полученной информации.

Знание о принципе работы оконной информационной технологии.

Получение конкретных знаний по физике, истории, психологии и других разделов (приведены в развертках).



thelawofenergyconservation, heatbalance, thermalconductivity, теплоемкость, сопротивление теплопередаче, иллюминатор, иллюзия, операционная система, родительская программа, окно



 Грабовская Лариса Леонидовна


Participated in the case upgrading:



The End

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Цікаві факти

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