A substance has the highest thermal conductivity in a solid. I. Organizational moment. What is conductivity
1. Introduction.
The project is designed in accordance with the standard of medium general education in physics. When writing this project, the study of thermal phenomena, their application in everyday life and technology was considered. In addition to theoretical material, much attention is paid to research work- these are experiments that answer the questions "In what ways can the internal energy of the body be changed", "Is the thermal conductivity the same various substances”, “Why do jets of warm air or liquid rise upwards”, “Why do bodies with a dark surface heat up more”; search and processing of information, photographs. Time of work on the project: 1 - 1.5 months. Project goals: * practical implementation of schoolchildren's knowledge about thermal phenomena; * formation of skills for independent research; * development of cognitive interests; * development of logical and technical thinking * development of abilities for independent acquisition of new knowledge in physics in accordance with vital needs and interests;
Besides the question of the number of dimensions that outer space seems to have, string theory also poses some other problems that need to be solved before we can declare it as the ultimate unified theory of physics. We still don't know if all infinities destroy each other, and how exactly we can connect waves to a string with special kind particles that we observe. However, we may find answers to these questions within the next few years, and by the end of the century we know whether string theory is the long-awaited unified theory of physics.
2. The main part.
2.1. Theoretical part
In life, we do encounter thermal phenomena every day. However, we do not always think that these phenomena can be explained if you know physics well. In physics lessons, we got acquainted with ways to change internal energy: heat transfer and doing work on the body or the body itself. When two bodies with different temperatures come into contact, energy is transferred from a body with more high temperature to a body with a lower temperature. This process will continue until the temperatures of the bodies are equal (thermal equilibrium is reached). In this case, no mechanical work is done. The process of changing internal energy without doing work on the body or the body itself is called heat transfer or heat transfer. In heat transfer, energy is always transferred from a hotter body to a cooler one. The reverse process never occurs spontaneously (by itself), i.e., heat transfer is irreversible. Heat transfer determines or accompanies many processes in nature: the evolution of stars and planets, meteorological processes on the Earth's surface, etc. Types of heat transfer: thermal conductivity, convection, radiation.
But can there be such a unified theory? There is simply an endless series of theories that more accurately and accurately describe the universe. Some will plead for a third possibility on the grounds that if there were a complete system of laws, it would prevent God from changing his mind and intervening in the world. Kind of like an old paradox: can God make a rock so heavy that he can't lift it? But the idea that God would like to change his mind is one example of the deceit that St. Augustine showed when he presented God as existing in time: time is a property of the universe created only by God.
thermal conductivity called the phenomenon of energy transfer from more heated parts of the body to less heated as a result of thermal motion and the interaction of the particles that make up the body.
Metals have the highest thermal conductivity - they have hundreds of times more than water. The exceptions are mercury and lead, but even here the thermal conductivity is ten times greater than that of water.
He probably knew what he meant when he said it! With the advent quantum mechanics we began to understand that events cannot be predicted with absolute accuracy, and there is always a certain degree of uncertainty. If you like, you can attribute this random character to God's intervention, but that would be a very strange intervention: there is no evidence that it is intentional. Indeed, if it were intentional, by definition it would not be accidental. Today we have practically abolished the third possibility and defined the goal of science: our task is to formulate a set of laws that allow us to predict events only up to the limit set by the uncertainty principle.
When lowering a metal needle into a glass with hot water very soon the end of the spoke became hot too. Consequently, internal energy, like any kind of energy, can be transferred from one body to another. Internal energy can also be transferred from one part of the body to another. So, for example, if one end of a nail is heated in a flame, then its other end, which is in the hand, will gradually heat up and burn the hand.
In many cases, we increased the sensitivity of our measurements or made new observations only to discover new phenomena that are not predicted by the existing theory and take them into account, we had to develop a better theory.
We might expect to find several new layers of structure more fundamental than quarks and electrons, which we now regard as "elementary" particles. But gravity allows you to set a boundary on this series of "boxes in boxes." If there is a particle of energy above the so-called Therefore, it is quite possible that a number of increasingly accurate theories have a certain limit as we approach higher energies, so there must be a certain theory of the universe. Of course, the Planck energy is very far from the energy of 100 ohms, which is the maximum that we are currently in the laboratory.
2.2. Practical part.
Let us study this phenomenon by doing a series of experiments with solids, liquids and gases.
Experience #1
Have taken various items: one aluminum spoon, another wooden spoon, a third plastic spoon, a fourth stainless steel spoon, and a fifth silver spoon. We attached paper clips to each spoon with drops of honey. They put spoons into a glass of hot water so that handles with paper clips stick out of it in different directions. The spoons will heat up, and as they heat up, the honey will melt and the paper clips will fall off.
In the foreseeable future, we are unlikely to reach the Planck energy! However, the most early stages The universe is the arena where such energies must arise. In my opinion, exploration of the early universe and the requirement of mathematical strength offer a good chance of getting to a complete unified theory while we're alive, if we haven't blown up before.
What does it mean if we actually found the ultimate theory of the universe? But if a theory is mathematically validated and always produces predictions that agree with observations, we can almost be sure it's true. This would bring to an end a long and glorious chapter in the history of man's intellectual battle to understand the universe. But it will also lead to a revolution in man's usual understanding of the laws that govern the universe. In Newton's time educated person could have an idea of all human knowledge, at least in general terms.
Of course, the spoons should be the same in shape and size. Where heating occurs faster, that metal conducts heat better, is more thermally conductive. For this experiment, I took a glass of boiling water and four types of spoons: aluminum, silver, plastic and stainless. I lowered them one by one into a glass and timed the time: in how many minutes it would heat up. That's what I did:
Conclusion: spoons made of wood and plastic take longer to heat up than spoons made of metal, which means that metals have good thermal conductivity.
Experience #2
Let's bring the end of a wooden stick into the fire. It will ignite. The other end of the stick, which is outside, will be cold. So the tree has poor thermal conductivity.
We bring the end of a thin glass rod to the flame of an alcohol lamp. After a while, it will heat up, while the other end will remain cold. Therefore, glass also has poor thermal conductivity.
If we heat the end of a metal rod in a flame, then very soon the entire rod will become very hot. We can no longer hold it in our hands.
This means that metals conduct heat well, that is, they have a high thermal conductivity. On the shta-ti-ve go-ri-zon-tal-but fortified-lyon ster-zhen. On the rod, through one-on-one space, ver-ti-kal-but fasten-le-na with the help of wax metal carnations.
To the edge of the rod, they put a candle under it. Since the edge of the rod is on the gre-va-et-sya, then in a degree-pen-but the ster-zhen pro-gre-va-et-sya. When the heat reaches the place where the carnations with the rod are fastened, the ste-a-rin melts, and the carnation falls. We see that in this experiment there is no pe-re-but-sa-substance, so-respectively-but, ob-observe-yes-there-is-warm-lo-water- ness.
Experience #3
Different metals have different thermal conductivity. In the physics room there is a device with which we can make sure that different metals have different thermal conductivity. However, at home, we were able to verify this with the help of a home-made device.
An instrument for displaying the various thermal conductivities of solids.
We have made a device for displaying different thermal conductivity of solids. To do this, we used an empty aluminum foil jar, two rubber rings (homemade), three pieces of wire made of aluminum, copper and iron, a tile, hot water, 3 figurines of little men with arms raised, cut out of paper.
The order of manufacture of the device:
bend the wire in the form of the letter "G";
strengthen them from the outside of the can with rubber rings;
hang paper men from the horizontal parts of the wire segments (using molten paraffin or plasticine).
Checking the operation of the device. Pour hot water into a jar (if necessary, heat a jar of water on an electric stove) and observe which figure will fall first, second, third.
Results. The figurine attached to the copper wire, the second - on aluminum, the third - on steel.
Conclusion. Different solids have different thermal conductivity.
The thermal conductivity of different substances is different.
Experience No. 4
Consider now the thermal conductivity of liquids. Take a test tube with water and begin to heat its upper part. The water at the surface will soon boil, and at the bottom of the tube during this time it will only heat up. This means that liquids have low thermal conductivity.
Experience No. 5
We investigate the thermal conductivity of gases. We put a dry test tube on the finger and heat it upside down in the flame of an alcohol lamp. The finger will not feel warm for a long time. This is due to the fact that the distance between gas molecules is even greater than that of liquids and solids. Therefore, the thermal conductivity of gases is even less.
Wool, hair, bird feathers, paper, snow and other porous bodies have poor thermal conductivity.
This is due to the fact that air is contained between the fibers of these substances. Air is a poor heat conductor.
So green grass is preserved under the snow, winter crops are preserved from freezing.
Experience No. 6
He fluffed up a small ball of cotton wool and wrapped it around the thermometer ball. Now he held the thermometer for some time at a certain distance from the flame and noticed how the temperature rose. Then the same ball of cotton squeezed and wrapped tightly around the bulb of the thermometer and again brought it to the lamp. In the second case, mercury will rise much faster. This means that compressed cotton wool conducts heat much better!
Vacuum (space freed from air) has the lowest thermal conductivity. This is explained by the fact that thermal conductivity is the transfer of energy from one part of the body to another, which occurs during the interaction of molecules or other particles. In a space where there are no particles, heat conduction cannot take place.
3. Conclusion.
Different substances have different thermal conductivity.
They have high thermal conductivity solid bodies(metals), lesser - liquids, and bad - gases.
We can use the thermal conductivity of various substances in everyday life, technology and nature.
The phenomenon of thermal conductivity is inherent in all substances, regardless of the state of aggregation they are in.
Now, without difficulty, I can answer and explain from a physical point of view to the questions:
1. Why do birds fluff their feathers in cold weather?
(There is air between the feathers, and air is a poor conductor of heat.)
2. Why do woolen clothes keep the cold better than synthetic ones?
(There is air between the hairs, which does not conduct heat well).
3. Why do cats sleep curled up in a ball when the weather is cold in winter? (Curled into a ball, they reduce the surface area that gives off heat).
4. Why are the handles of soldering irons, irons, pans, pots made of wood or plastic? (Wood and plastic have poor thermal conductivity, so when we heat metal objects, holding a wooden or plastic handle will not burn our hands).
5. Why are bushes of heat-loving plants and bushes covered with sawdust for the winter?
(Sawdust is a poor conductor of heat. Therefore, plants are covered with sawdust so that they do not freeze).
6. Which boots protect against frost better: tight or spacious?
(Spacious, since air does not conduct heat well, it is another layer in the boot that retains heat).
4. List of used literature.
Printed editions:
1.A.V. Peryshkin Physics Grade 8 -M: Bustard, 2012
2.M.I.Bludov Conversations on physics part 1 -M: Enlightenment 1984.
Internet resources:
1.http://class-fizika.narod.ru/8_3.htm
2.http://ru.wikipedia.org/wiki/%D0%A2%D0%B5%D0%BF%D0%BB%D0%BE%D0%BF%D1%80%D0%BE%D0%B2 %D0%BE%D0%B4%D0%BD%D0%BE%D1%81%D1%82%D1%8C