Read Text C and explain what the concept of antimatter is.

Text C. Matter and antimatter.

Before the 20th century, the term matter included ordinary matter composed of atoms and excluded other energy phenomena such as light or sound. This concept of matter may be generalized from atoms to include any objects having mass even when at rest, but this is ill-defined because an object's mass can arise from its (possibly massless) constituents' motion and interaction energies. Thus, matter does not have a universal definition, nor is it a fundamental concept in physics today. Matter is also used loosely as a general term for the substance that makes up all observable physical objects.

All the objects from everyday life that we can bump into, touch or squeeze are composed of atoms. This atomic matter is in turn made up of interacting subatomic particles - usually a nucleus of protons and neutrons, and a cloud of orbiting electrons. Typically, science considers these composite particles matter because they have both rest mass and volume. By contrast, massless particles, such as photons, are not considered matter, because they have neither rest mass nor volume. However, not all particles with rest mass have a classical volume, since fundamental particles such as quarks and leptons (sometimes equated with matter) are considered "point particles" with no effective size or volume. Nevertheless, quarks and leptons together make up "ordinary matter", and their interactions contribute to the effective volume of the composite particles that make up ordinary matter.

Matter exists in states (or phases): the classical solid, liquid, and gas; as well as the more exotic plasma, Bose–Einstein condensates, fermionic condensates, and quark–gluon plasma.

In particle physics and quantum chemistry, antimatter is matter that is composed of the antiparticles of those that constitute ordinary matter. If a particle and its antiparticle come into contact with each other, the two annihilate; that is, they may both be converted into other particles with equal energy in accordance with Einstein's equation E = mc². These new particles may be high-energy photons (gamma rays) or other particle–antiparticle pairs. The resulting particles are endowed with an amount of kinetic energy equal to the difference between the rest mass of the products of the annihilation and the rest mass of the original particle–antiparticle pair, which is often quite large.

Antimatter is not found naturally on Earth, except very briefly and in vanishingly small quantities (as the result of radioactive decay, lightning or cosmic rays). This is because antimatter that came to exist on Earth outside the confines of a suitable physics laboratory would almost instantly meet the ordinary matter that Earth is made of, and be annihilated. Antiparticles and some stable antimatter (such as antihydrogen) can be made in tiny amounts, but not in enough quantity to do more than test a few of its theoretical properties.

8. Find Russian equivalents of the following terms from Text C:

to exclude; constituents; observable; massless particles; rest mass; quark; point particles; interaction; Bose–Einstein condensates; fermionic; quark–gluon plasma; quantum chemistry; to constitute; to annihilate; gamma rays; annihilation; quantity; radioactive decay.

9. Comprehension check. Answer the questions on Text C:

1. How was the term matter defined before the 20th century?

2. Why aren’t photons considered matter?

3. What interacting subatomic particles is the atomic matter made of?

4. Why does science consider these composite particles matter?

5. How many states of matter are there according to the text?

6. What is antimatter composed of?

7. Why can’t antimatter be found naturally on Earth?

10. Speaking task: work in groups. Imagine you are taking part in a scientific conference. Give a presentation devoted to one of the states of matter (solid, liquid, gas or plasma). Get ready to answer any questions about the topic of your presentation. Vote for the best presentation of the conference.

UNIT V. INORGANIC CHEMISTRY.

How can you define inorganic chemistry? What inorganic compounds can you name? Read Text A and check your answers.