Материал: Андрианова English Thesaurus of Student-Physicist 2013

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An ideal gas is a collection of atoms or molecules that move randomly and exert no long-range forces on each other. Each particle of the ideal gas is individually point-like, occupying a negligible volume. A gas usually consists of a very large number of particles, so it's convenient to express the amount of gas in a given volume in terms of the number of moles.

1.Why do we need the concepts of temperature, heat and internal

energy?

2.What is called heat?

3.Formulate the zeroth law of thermodynamics.

4.What physical property do thermometers use?

5.What is the most common temperature scale in use in the United

States?

6.Give examples of thermal expansion playing an important role in multiple applications.

7.Give the definition of an ideal gas.

Exercises

1. Rearrange the letters in the anagrams to form equivalents for the Russian words:

2. Match the words in A with the words in B to form word combinations:

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3. Fill in the gaps with the missing words from the list:

thermal expansion, thermal contact, freezing point, thermal equilibrium, thermometer

1.Two objects are in _____ if energy can be exchanged between

them.

2.Two objects are in _____ if they are in thermal contact and there is no net exchange of energy.

3.On the Celsius scale, the temperature of the ice-water mixture is defined to be zero degrees Celsius, written 0°C and called the ice point or _____ of water.

4.Experiments show that the _____ readings are nearly independent of the type of gas used, as long as the gas pressure is low and the temperature is well above the point at which the gas liquifies.

5.If the _____ of an object is sufficiently small compared with the object's initial dimensions, then the change in any dimension is, to a good approximation, proportional to the first power of the temperature change.

UNIT 11

ENERGY IN THERMAL PROCESSES

Read the following texts. Study the thesaurus on fig. 11, answer the questions after the texts

When two objects with different temperatures are placed in thermal contact, the temperature of the warmer object decreases while the temperature of the cooler object increases. With time, they reach a common equilibrium temperature somewhere in between their initial temperatures. During this process, we say that energy is transferred from the warmer object to the cooler one.

Until about 1850, the subjects of thermodynamics and mechanics were considered two distinct branches of science, and the principle of conservation of energy seemed to describe only certain kinds of mechanical systems. Experiments performed by the English physicist James Joule (18181889) and others showed that the decrease in mechanical energy (kinetic plus potential) of an isolated system was equal to the increase in internal energy of the system. Today, internal energy is treated as a form of energy that can be transformed into mechanical energy and vice versa. Once the

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concept of energy was broadened to include internal energy, the law of conservation of energy emerged as a universal law of nature.

Heat and internal energy

A major distinction must be made between internal energy and heat. These terms are not interchangeable - heat involves a transfer of internal energy from one location to another. The following formal definitions will make the distinction precise.

Internal energy is the energy associated with the microscopic components of a system - the atoms and molecules of the system. The internal energy includes kinetic and potential energy associated with the random translational, rotational, and vibrational motion of the particles that make up the system, and any potential energy bonding the particles together. Heat is the transfer of energy between a system and its environment due to a temperature difference between them.

Early in the development of thermodynamics, before scientists realized the connection between thermodynamics and mechanics, heat was defined in terms of the temperature changes it produced in an object, and a separate unit of energy, the calorie, was used for heat.

Specific heat

The historical definition of the calorie is the amount of energy necessary to raise the temperature of one gram of a specific substance - water - by one degree. The amount of energy required to raise the temperature of one kilogram of an arbitrary substance by 1° varies with the substance. Every substance requires a unique amount of energy per unit mass to change the temperature of that substance by 1.0°C.

High specific heat is responsible for the moderate temperatures found in regions near large bodies of water. As the temperature of a body of water decreases during winter, the water transfers energy to the air, which carries the energy landward when prevailing winds are toward the land. Off the western coast of the United States, the energy liberated by the Pacific Ocean is carried to the east, keeping coastal areas much warmer than they would otherwise be. Winters are generally colder in the eastern coastal states, because the prevailing winds tend to carry the energy away from land.

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Fig. 11. Thesaurus for Unit 11

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