IV. Match (21-30) with their definitions (A-L). There are two definitions that you do not need to use.

21.	matter	A.	an electrically neutral group of at least two atoms held together by covalent chemical bonds
22.	motion	B.	to be real or present
23.	molecule	C.	a state of matter similar to gas in which a certain portion of the particles are ionized
24.	exist	D.	any movement or change in position or place
25.	disorganize	E.	to watch or be present without participating actively
26.	plasma	F.	a steady flow of a fluid (usually from natural causes
27.	observe	G.	conclude by reasoning; in logic
28.	modify	H.	a general term for the substance of which all physical objects consist
29.	emit	I.	to change in form or character; alter
30.	dissociation	J.	an arrehnius acid commonly pertains to the acid in water
		K.	to give or send forth (heat, light, a smell, etc
		L.	to destroy the systematic arrangement

Supplementary Tasks :

I. For statements (1-10) choose the best alternative (A, B or C) to replace the expressions in italics:

1. Matter in bulk comprises particles ... (line 1)

A.excludes B.includes C.conserves

2. ... a review of the effects of radiation on matter..(line 6)

A.consideration B. discussion C.survey

3. A glass appears to be solid ... (line 9)

A.approvesB.seemsC.looks

4. Plasmas, by contrast, are regions of high density and temperature... (line 14)

A.linesB.fieldsC.districts

5. The capability of analyzing and understanding matter depends on the details... (line 17)

A. relies B. comments C.focusses

6. ... by the senses supplemented by the more common scientific instruments... (line 19)

A. ordinary B. real C. true

7. It can be characterized by measurement of its mass, weight, etc. ... (line 22)

A.revealedB.calculatedC.distinguished

8. ... by which its observable character is modified (line 24).

A.restrictedB.transformedC.determined

9. Energy absorption, which always entails some kind of excitation... (line 25)

A.happensB.involvesC.produces

10. Atomic nuclei themselves may exist in various states... (line 29)

A.stable B. numerous C. different

IV. Determine the key message of the text. Choose the best alternative (A, B, C, D or E):

A. In matter in bulk the motion of the molecules doesn’t stop.

B. Matter, existing in three forms is presented in different states.

C. Matter can be characterized by optical phenomena.

D. The level of energy absorption depends on the existence of ground state and energy levels.

E. Structure and properties of matter depend on temperature, medium, exitation and other factors.

TEXT 15

MECHANICS

(1)Mechanics is generally taken to mean the study of the motion of objects under the action of given forces. In classical mechanics the laws are initially formulated for the point particles in which the dimensions, shapes, and other intrinsic properties of bodies are ignored. Thus in the first approximation even objects as large as the Earth and the Sun are treated as point like. (2)In rigid-body dynamics, the extension of bodies and their mass distributions are considered as well, but they are imagined to be incapable of deformation. The mechanics of deformable solids is elasticity; hydrostatics and hydrodynamics treat, respectively, fluids at rest and in motion. (3)The three laws of motion set forth by Isaac Newton form the foundation of classical mechanics, together with the recognition that forces are vector quantities. The first law states that, unless acted upon by an external force, an object at rest remains at rest, or if in motion, it continues to move in a straight line with constant speed. Uniform motion therefore does not require a cause. Accordingly, mechanics concentrates not on motion as such but on the change in the state of motion of an object that results from the net force acting upon it. (4)Newton’s second law equates the net force on an object to the rate of change of its momentum, the latter being the product of the mass of a body and its velocity. Newton’s third law states that when two particles interact, the forces each exerts on the other are equal in magnitude and opposite in direction. (5)Taken together, these mechanical laws in principle permit the determination of the future motions of a set of particles, their state of motion at some instant, as well as the forces that act between them and upon them from the outside. Lying at the most basic level of physics, the laws of mechanics are characterized by certain symmetry properties, as exemplified in the aforementioned symmetry between action and reaction forces. Other symmetries, such as the invariance (i.e., unchanging form) of the laws under reflections and rotations carried out in space, reversal of time, or transformation to a different part of space or to a different epoch of time, are present both in classical mechanics and in relativistic mechanics, and with certain restrictions, also in quantum mechanics.