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Text 3. The Laws of thermodynamics
The term thermodynamics was coined by James Joule in 1859 to designate the science of relations between heat and power. By 1858, ‘thermo-dynamics’, as a functional term, was used in William Thomson’s paper “An Account of Carnot’s Theory of the Motive Power of Heat”. The first textbook in thermodynamics was written in 1859 by William Rankine, originally trained as a physicist and mechanical engineering professor at the University of Glasgow. Thermodynamics is the study of the conversion of heat energy into different forms of energy.
In thermodynamics, there are four laws of very general validity, they do not depend on the details of the interactions or the systems being studied. Hence, they can be applied to systems about which one knows nothing other than the balance of energy and matter transfer. Examples of this include Einstein’s prediction of spontaneous emission around the turn of the 20th century and current research into the thermodynamics of black holes.
The four laws are:
- Zeroth law of thermodynamics, stating that thermodynamic equilibrium is an equivalence relation.
If two thermodynamic systems are separately in thermal equilibrium with a third one, they are also in thermal equilibrium with each other. It is assumed in every measurement of temperature. Thus, if we want to know if two objects have the same temperature, it is not necessary to bring them into contact and see whether their observable properties change with time.
A system in thermal equilibrium is a system whose macroscopic properties (like pressure, temperature, volume, etc.) are not changing in time. A hot cup of coffee on a kitchen table is not in equilibrium with its surroundings because it is cooling off and decreasing in temperature. Once its temperature stops decreasing, it will be at room temperature, and it will be in thermal equilibrium with the surroundings.
The first law of thermodynamics basically states that a thermodynamic system can store or hold energy and that this internal energy is conserved. Heat is a process by which energy is added to a system from a high-temperature source. In addition, energy may be lost by the system when it does mechanical work on its surroundings, or conversely, it may gain energy as a result of work done on it by its surroundings. The first law states that this energy is conserved. The change in the internal energy is equal to the amount added by heating minus the amount lost by doing work on the environment.
There are many statements of the second law which use different terms, but they are all equivalent. The simplest formulation of the second law is: heat cannot flow spontaneously from a lower-temperature material to a higher-temperature material. It is obviously true from everyday experience. For example, in a refrigerator heat flows from cold to hot, but only when electrical energy is added. Note that from the mathematical definition of entropy, a process in which heat flows from cold to hot has decreasing entropy.
The formulation of the second law given by Lord Kelvin is the following:
It is impossible to convert heat completely into work. It is impossible to extract energy by heat from a high-temperature energy source and then convert all of the energy into work. Thus, a heat engine with 100% efficiency is thermodynamically impossible.
The third law of thermodynamics is about absolute zero temperature.
As a system asymptotically approaches the temperature of absolute zero, all processes virtually cease and the entropy of the system asymptotically approaches a minimum value. It is impossible to reach the temperature of absolute zero by any finite number of processes.
Exercise 33. Define the parts of speech and translate the words.
a) designate – designation; observe – observation – observer; measure – measurement; heat – heater; transmit – transmission; generate – generator – generation; extract – extraction; equilibrate – equilibrium; relate – relation; convert – converter – conversion; apply – application; emit – emitter – emission; transform – transformation – transformer.
b) equivalence – equivalent; spontaneity – spontaneous; practice – practical; power – powerful; mechanic – mechanical; validity – valid; observation – observable; variety – various; practice – practical; use – usual; base – basic; difference – different.
c) usual – usually; continuous – continuously; spontaneous - spontaneously; obvious – obviously; practical – practically; potential - potentially; basic – basically; converse – conversely; equal – equally; virtual – virtually; increasing – increasingly; different – differently.
Exercise 34. Give the initial form of the following words. Define the parts of speech and translate.
a) better, lower, higher, hotter, less, greatest, older, more, best, worse, most, worst, farther, further, elder.
b) written, known, held, lost, left, decreased, converted, given, found, situated, driven, spread, undergone, been, applied.
Exercise 35. Translate and comment upon the following verb forms.
Was coined; can be applied; is assumed; being studied; can store; may be lost; does; will be decreasing; have been explained; have reached; is converting; being defined; are to be; must have written; stopped increasing.
Exercise 36. Translate the following word combinations into Ukrainian.
Spontaneous emission, current research, thermal equilibrium, measurement of temperature, macroscopic properties, mathematical definition, formulation of the law, high-temperature energy source, heat engine, absolute zero, finite number of processes, engine efficiency, leading scientists.
Exercise 37. Complete the sentences with English equivalents of the words in brackets.
1. Boyle and Hooke noticed a correlation between (тиском), (температурою) and (об’ємом).
2. Boyle’s Law states that pressure and volume are (обернено пропорційні).
3. Energy may be lost by the system when it does (механічну роботу) on its surroundings.
4. It is impossible to (перетворити) heat completely into work.
5. Thermodynamics describes how systems (реагують) to changes in their (оточенні).
6. The starting point for most thermodynamic considerations are (закони термодинаміки).
7. By watching (клапан) rhythmically move up and down, Papin conceived the idea of (поршневого двигуна).
Exercise 38. Work in pairs. Translate the following questions and answer them.
1.Що вивчає термодинаміка?
2.Як визначаються «система» і «оточуюче середовище» у термодинаміці?
3.Скільки існує законів термодинаміки?
4.Якого вченого можна вважати засновником термодинаміки?
5.Що таке термодинамічна рівновага?
6.Чи існує багато формулювань другого закону термодинаміки? Чим це пояснюється?
7.Яким чином відбувається теплообмін між предметами різної температури? Наведіть приклади.
8.Що таке ентропія?
9.Яке співвідношення існує між тиском, температурою і об’ємом?
Exercise 39. Say whether the following statements are true or false. Correct them if necessary.
1. There are three laws of thermodynamics.
2. The first engine was built by Boyle and Hooke?
3. Sadi Carnot designed the world’s first vacuum pump.
4. Heat moves from a low-temperature source to a high-temperature source.
5. The new textbook on thermodynamics has already been written.
6. The system gains energy when it does mechanical work.
7. It is possible to reach the temperature of absolute zero by any finite number of processes.
8. A thermodynamic system can’t store or hold energy.
9. Internal energy is always conserved.
10. A heat engine with 100% efficiency is thermodynamically possible.
Exercise 40. Speak on “Four Laws of Thermodynamics”.
Exercise 41. Memorize the following words and word combinations to text 4.
Chemical energy – хімічна енергія
heat energy – теплова енергія
radiant energy – енергія випромінювання
Btu (British thermal unit) – британська теплова одиниця
invent – винаходити
sea level – рівень моря
equal – однаковий; рівнятися, дорівнювати
match – сірник
weigh – важити; зважувати
height – висота
exist – існувати
destroy – знищувати
flash light – ручний електричний ліхтар
occur – відбуватися, мати місце
stir – розмішувати
convection – конвекція
empty – порожній
Exercise 42. Read and translate text 4. Make up the plan of the key ideas.