2. Read the words from the text, make stress on the right syllable.

possess	total mass
inherent	diminish
quantity	equivalent
assumption	distribution
ash	alter

Text the law of conservation of mass and energy

All bodies possess mass, which is an inherent property of all matter. In our experiences we have observed that the outward appearance of matter is constantly changing, so that it would reasonable to assume that its mass is also undergoing some sort of change. To test this assumption let us take a lump of coal and burn it. The mass of this lump is certainly much greater than the ashes that result from its burning, but should we collect the gases formed and account for all the other materials concerned in the burning and weight them, we should find that the total mass has remained unchanged. All the experience accumulated in the study of every change in matter shows that in all the changes the total mass is neither increased nor diminished.

But every change in matter involves a change in energy. This energy makes its appearance in a number of forms such as heat, energy, electrical energy, chemical energy, radiant energy, kinetic energy (energy possessed by moving bodies), or potential energy.

Experiments carried out over a long period of time have shown that energy is like mass in that energy in all transformations is neither created nor destroyed. This generalization is known as the law of conservation of energy. The distribution of this energy between bodies, however, is altered without a great deal of difficulty. For example, if a piece of hot metal is placed into cold water, the metal is cooled and the water is heated so that the metal loses energy and the water gains it. We also find that energy can be freely transformed from one variety to another. Thus the heat energy derived from the burning of coal may be changed into the kinetic energy of the locomotive. Similarly, the kinetic energy possessed by falling water can be transformed into electricity. If we were to make a close study of such transformations, we should find that a definite quantity of energy of one kind always gives a definite equivalent quantity of another.

In any action involving the change of one form of energy into another no gain or loss in total energy takes place. In other words: whenever a quantity of one kind of energy is produced, an exactly equivalent amount of another kind must be used up.

Both the principle of conservation of mass and the principle of preservation of energy afford a simple, direct approach in setting up a material balance and an energy balance. In both cases a relatively complete accounting can be made from the knowledge of what goes into the system and what comes out, what is the efficiency of a given system, whether it is a blast furnace or a locomotive.

Notes to the text:

1. inherent	невід’ємний
2. outward appearance	зовнішній появ
3. assumption	припущення
4. distribution…is altered	розподіл ... відбувається
5. to destroy	руйнувати
6. no gain or loss in total energy takes place	не відбувається ні збільшення, ні зменшення загальної кількості енергії
7. radiant energy	променева енергія
8. close study	детальне вивчення
9. conservation of mass	збереження маси
10. amount	кількість
11. relatively	відносно
12. to afford	дозволити
13. blast furnace	домна