Учебное пособие Казань-2016 Сайфуллина М. Н., Хабирова Н. М. English for Physicists

34 
sublimation, n. 
/ˌsʌblɪˈmeɪʃən/ 
испарение 
твердых 
тел, 
сублимация 
temperature, n. 
/ˈtemprətʃər/ 
температура 
vapor, n. 
/ˈveɪpər/ 
пар 
volume, n. 
/ˈvɒljuːm/ 
объем 
weak, adj. 
/wiːk/ 
слабый, неустойчивый 
 
READING 
Read and translate the text using a dictionary if necessary: 
The kinetic molecular theory of matter offers a description of the 
microscopic properties of atoms (or molecules) and their interactions, 
leading to observable macroscopic properties (such as pressure, volume, 
temperature). An application of the theory is that it helps to explain why 
matter exists in different phases (solid, liquid, and gas) and how matter can 
change from one phase to the next. 
The three phases of matter: 
Notice that the spacing between atoms or molecules increases as we 
move from a description of the solid phase to the gaseous one. The kinetic 
molecular theory of matter states that: 
Matter is made up of particles that are constantly moving. 
All particles have energy, but the energy varies depending on the 
temperature the sample of matter is in. This in turn determines 
whether the substance exists in the solid, liquid, or gaseous state. 
Molecules in the solid phase have the least amount of energy, while 
gas particles have the greatest amount of energy. 
The temperature of a substance is a measure of the average kinetic 
energy of the particles. 

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A change in phase may occur when the energy of the particles is 
changed. 
There are spaces between particles of matter. The average amount of 
empty space between molecules gets progressively larger as a sample 
of matter moves from the solid to the liquid and gas phases. 
There are attractive forces between atoms/molecules, and these 
become stronger as the particles move closer together. These 
attractive forces are called intermolecular forces. 
Let's take water as an example. We find that in its solid phase (ice), the 
water molecules have very little energy and cannot move away from each 
other. The molecules are held closely together in a regular pattern called a 
lattice. If the ice is heated, the energy of the molecules increases. This 
means that some of the water molecules are able to overcome the 
intermolecular forces that are holding them close together, and the 
molecules move further apart, forming liquid water. This is why liquid
water is able to flow: the molecules have greater freedom to move than they 
had in the solid lattice. 
If the molecules are heated further, the liquid water will become water 
vapor, which is a gas. Gas particles have more energy and are on average at 
distances from each other which are much larger than the size of the 
atoms/molecules themselves. The attractive forces between the particles are 
very weak given the large distances between them. The illustration below 
shows a change in phase. 
The kinetic theory of matter is also illustrated by the process of 
diffusion. Diffusion is the movement of particles from a high concentration 
to a low concentration. It can be seen as a spreading-out of particles 
resulting in their even distribution. Placing a drop of food coloring in water 
provides a visual representation of this process – the color slowly spreads 
out through the water. If matter were not made of particles, then we would 

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simply see a clump of color, since there would be no smaller units that 
could move about and mix in with the water. 
(Adopted from 
www.boundless.com 
) 
 
 
 
 

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