The state of aggregation of a substance is usually called its ability to maintain its shape and volume. An additional feature is the methods of transition of a substance from one state of aggregation to another. Based on this, three states of aggregation are distinguished: solid, liquid and gas. Their visible properties are:
A solid body retains both shape and volume. It can pass either into a liquid by melting or directly into a gas by sublimation.
- Liquid – retains volume, but not shape, that is, it has fluidity. Spilled liquid tends to spread indefinitely over the surface on which it is poured. A liquid can become a solid by crystallization, and a gas by evaporation.
- Gas – does not retain either shape or volume. Gas outside any container tends to expand unlimitedly in all directions. Only gravity can prevent him from doing this, due to which the earth’s atmosphere does not dissipate into space. Gas passes into a liquid by condensation, and directly into a solid by sedimentation.
Phase transitions
The transition of a substance from one state of aggregation to another is called a phase transition, since the scientific state of aggregation is the phase of matter. For example, water can exist in the solid phase (ice), liquid (plain water) and gaseous phase (water vapor).
The example of water is also well demonstrated. Hung out in the yard to dry on a frosty, windless day, it immediately freezes, but after some time it turns out to be dry: the ice sublimates, directly turning into water vapor.
As a rule, a phase transition from a solid to a liquid and gas requires heating, but the temperature of the medium does not increase: thermal energy is spent on breaking internal bonds in the substance. This is the so-called latent heat. During reverse phase transitions (condensation, crystallization), this heat is released.
This is why steam burns are so dangerous. When it gets on the skin, it condenses. The latent heat of evaporation/condensation of water is very high: water in this regard is an anomalous substance; This is why life on Earth is possible. In a steam burn, the latent heat of condensation of water “scalds” the burned area very deeply, and the consequences of a steam burn are much more severe than from a flame on the same area of the body.
Pseudophases
The fluidity of the liquid phase of a substance is determined by its viscosity, and viscosity is determined by the nature of the internal bonds, which are discussed in the next section. The viscosity of the liquid can be very high, and such liquid can flow unnoticed by the eye.
A classic example is glass. It is not a solid, but a very viscous liquid. Please note that sheets of glass in warehouses are never stored leaning diagonally against the wall. Within a few days they will bend under their own weight and will be unfit for consumption.
Other pseudo-solids are shoe polish and construction pitch. If you forget the angular piece on the roof, over the summer it will spread into a cake and stick to the base. Pseudo-solid bodies can be distinguished from real ones by the nature of melting: real ones with it either retain their shape until they immediately spread (solder with), or float, releasing puddles and streams (ice). And very viscous liquids gradually soften, like pitch or bitumen.
Plastics are extremely viscous liquids, the fluidity of which is not noticeable for many years and decades. Their high ability to retain shape is ensured by the huge molecular weight of polymers, many thousands and millions of hydrogen atoms.
Phase structure of matter
In the gas phase, the molecules or atoms of a substance are very far apart from each other, many times greater than the distance between them. They interact with each other occasionally and irregularly, only during collisions. The interaction itself is elastic: they collided like hard balls and immediately scattered.
In a liquid, molecules/atoms constantly “feel” each other due to very weak bonds of a chemical nature. These bonds break all the time and are immediately restored again; the molecules of the liquid continuously move relative to each other, which is why the liquid flows. But to turn it into gas, you need to break all the bonds at once, and this requires a lot of energy, which is why the liquid retains its volume.
In this regard, water differs from other substances in that its molecules in the liquid are connected by so-called hydrogen bonds, which are quite strong. Therefore, water can be a liquid at a temperature normal for life. Many substances with a molecular weight tens and hundreds of times greater than that of water are, under normal conditions, gases, like ordinary household gas.
In a solid, all its molecules are firmly in place due to strong chemical bonds between them, forming a crystal lattice. Crystals of regular shape require special conditions for their growth and therefore are rare in nature. Most solids are conglomerates of small and tiny crystals – crystallites – tightly coupled by mechanical and electrical forces.
If the reader has ever seen, for example, a cracked axle shaft of a car or a cast iron grate, then the grains of crystallites on scrap are visible to the naked eye. And on fragments of broken porcelain or earthenware they can be observed under a magnifying glass.
Plasma
Physicists also identify a fourth state of matter – plasma. In plasma, electrons are separated from atomic nuclei, and it is a mixture of electrically charged particles. Plasma can be very dense. For example, one cubic centimeter of plasma from the interior of stars - white dwarfs - weighs tens and hundreds of tons.
Plasma is isolated into a separate state of aggregation because it actively interacts with electromagnetic fields due to the fact that its particles are charged. In free space, plasma tends to expand, cooling and turning into gas. But under the influence, it can retain its shape and volume outside the vessel, like a solid body. This property of plasma is used in thermonuclear power reactors - prototypes of power plants of the future.
>>Physics: Aggregate states of matter
In winter, water on the surface of lakes and rivers freezes, turning into ice. Under the ice, the water remains liquid. There are two different things that exist here at the same time. state of aggregation water - solid (ice) and liquid (water). There is a third state of water - gaseous: invisible water vapor is found in the air around us.
Different states of aggregation exist for each substance. These states differ from each other not by molecules, but by how these molecules are located and how they move. The features of the arrangement of molecules in different states of aggregation of the same substance - water - are illustrated in Figure 76.
Under certain conditions, substances can change from one state to another. All possible transformations in this case are displayed in Figure 77. The letters T, F and G indicate, respectively, the solid, liquid and gaseous states of the substance; arrows indicate the direction in which a particular process occurs.
In total, there are six processes in which aggregate transformations of matter occur. 
The transition of a substance from a solid (crystalline) state to a liquid is called melting crystallization or hardening. An example of melting is the melting of ice; the reverse process occurs when water freezes.
The transition of a substance from a liquid to a gaseous state is called vaporization, the reverse process is called condensation(from the Latin word "condensation" - compaction, thickening). An example of vaporization is the evaporation of water; condensation can be observed during the formation of dew.
The transition of a substance from a solid to a gaseous state (bypassing the liquid) is called sublimation(from the Latin word “sublimo” - I lift up) or sublimation, the reverse process is called desublimation. For example, graphite can be heated to a thousand, two thousand and even three thousand degrees, and yet it will not turn into a liquid: it will sublimate, that is, it will immediately go from a solid state to a gaseous state. The so-called “dry ice” (solid carbon monoxide CO 2), which can be seen in containers for storing and transporting ice cream, also immediately turns into a gaseous state (bypassing the liquid one). All odors possessed by solids (for example, naphthalene) are also caused by sublimation: when molecules fly out of a solid, they form a gas (or vapor) above it, which causes the sensation of smell.
An example of desublimation is the formation of patterns of ice crystals on windows in winter. These beautiful patterns are the result of desublimation of water vapor in the air.
Transitions of matter from one state of aggregation to another play an important role not only in nature, but also in technology. For example, by turning water into steam, we can then use it in steam turbines in power plants. By melting metals in factories, we get the opportunity to make various alloys from them: steel, cast iron, brass, etc. To understand all these processes, you need to know what happens to a substance when its state of aggregation changes and under what conditions this change is possible. This will be discussed in the following paragraphs.
1. Name the three states of matter of matter. 2. List all possible processes in which a substance passes from one state of aggregation to another. 3. Give examples of sublimation and desublimation. 4. What practical applications of aggregate transformations do you know? 5. Which letter (a, b or c) in Figure 76 indicates the solid state of water, liquid and gaseous?
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A complete list of topics by grade, answers to tests, calendar plan according to the school physics curriculum, physics courses and assignments for grade 8, ready-made homework and solutions, all physics online
Lesson content lesson notes and supporting frame lesson presentation interactive technologies accelerator teaching methods Practice tests, testing online tasks and exercises homework workshops and trainings questions for class discussions Illustrations video and audio materials photographs, pictures, graphs, tables, diagrams, comics, parables, sayings, crosswords, anecdotes, jokes, quotes Add-ons abstracts cheat sheets tips for the curious articles (MAN) literature basic and additional dictionary of terms Improving textbooks and lessons correcting errors in the textbook, replacing outdated knowledge with new ones Only for teachers calendar plans training programs methodological recommendationsAny body can be in different states of aggregation at a certain temperature and pressure - in solid, liquid, gaseous and plasma states.
For a transition from one state of aggregation to another, it occurs under the condition that the heating of the body from the outside occurs faster than its cooling. And vice versa, if the cooling of the body from the outside occurs faster than the heating of the body due to its internal energy.
When transitioning to another state of aggregation, the substance remains the same, the same molecules will remain, only their relative arrangement, speed of movement and forces of interaction with each other will change.
Those. a change in the internal energy of the particles of a body transfers it from one phase of the state to another. Moreover, this state can be maintained in a wide temperature range of the external environment.
When changing the state of aggregation, a certain amount of energy is needed. And during the transition process, energy is spent not on changing the body temperature, but on changing the internal energy of the body.
Let us display on the graph the dependence of body temperature T (at constant pressure) on the amount of heat Q supplied to the body during the transition from one state of aggregation to another.
Consider a body with mass m, which is in a solid state at a temperature T 1.
The body does not immediately transition from one state to another. First, energy is needed to change internal energy, and this takes time. The rate of transition depends on the mass of the body and its heat capacity.
Let's start heating the body. Using formulas you can write it like this:
Q = c⋅m⋅(T 2 -T 1)
The body must absorb so much heat in order to heat up from temperature T1 to T2.
Transition from solid to liquid
Further, at the critical temperature T2, which is different for each body, intermolecular bonds begin to break down and the body passes into another state of aggregation - liquid, i.e. intermolecular bonds weaken, molecules begin to move with greater amplitude, greater speed and greater kinetic energy. Therefore, the temperature of the same body in a liquid state is higher than in a solid state.
In order for the entire body to pass from a solid to a liquid state, it takes time to accumulate internal energy. At this time, all the energy goes not to heating the body, but to the destruction of old intermolecular bonds and the creation of new ones. Amount of energy needed:
λ - specific heat of melting and crystallization of a substance in J/kg, different for each substance.
After the entire body has passed into a liquid state, this liquid again begins to heat up according to the formula: Q = c⋅m⋅(T-T 2); [J].
Transition of a body from liquid to gaseous state
When a new critical temperature T 3 is reached, a new process of transition from liquid to vapor begins. To move further from liquid to vapor, you need to expend energy:
r is the specific heat of gas formation and condensation of a substance in J/kg, different for each substance.
Note that a transition from the solid state to the gaseous state is possible, bypassing the liquid phase. This process is called sublimation, and its inverse process is desublimation.
Transition of a body from a gaseous state to a plasma state
Plasma- a partially or fully ionized gas in which the densities of positive and negative charges are almost equal.
Plasma usually occurs at high temperatures, from several thousand °C and above. Based on the method of formation, two types of plasma are distinguished: thermal, which occurs when gas is heated to high temperatures, and gaseous, which is formed during electrical discharges in a gaseous environment.
This process is very complex and has a simple description, and it is not achievable for us in everyday conditions. Therefore, we will not dwell on this issue in detail.
For a critically minded person, observations of how their physiological characteristics change when people transition from one state to another can be very interesting and useful. For example, posture and tone of voice can change almost instantly. By observing others, you can discover a lot about yourself, especially if until now you thought that you lacked creative energy, or that you lacked realism, or that you were a bad organizer. You can modify Disney's strategy model somewhat—for example, in your home, use different rooms or chairs to represent different positions. But remember to follow the following important rules of NLP:
Each position should have a corresponding tangible “anchor”, such that you invariably associate it with a certain state (just as you associate your favorite chair with relaxation).
Before entering any new state, exit the previous one (therefore it is advisable to use different positions in space for different states). Otherwise, there is a danger of taking with you elements of the previous state when transitioning to a new one, “sitting on two chairs at once.”
Practice as much as possible (just like learning any other technique) and be flexible. The Disney strategy model can be applied to a wide variety of situations, both in relation to people and in relation to processes, slow or fast.
All these are nothing more than models and techniques, but in practice you are free to think as you see fit and change your point of view as you wish. The purpose of the above exercise is to help you learn how to instantly move from one state to another if necessary (for example, in case of sudden danger). If you can imagine yourself entering a particular room or sitting in a particular chair, these images can evoke the same associations as actual physical actions. The ability to create such reinforcing “anchors” for oneself is a necessary condition for the learning process.
Modeling ourselves
Previously, we considered modeling as identifying the activity strategies of people who have achieved excellence in any area, and reproducing these strategies in their activities. Disney's strategy model, however, clearly shows that we can also rely on our own memories. Inside each of us there is a dreamer, a realist and a critic who, under certain conditions, can act for our benefit. Thus, each of us has the internal resources necessary to improve the efficiency of our activities. If you've ever had a strong drive, been confident, felt like everything depended on you, been creative, persistent, and willing to take meaningful risks, then you don't need to look for a role model. Just move one of the their effective strategies into a new field of activity. For example, from the field of sports to the professional sphere. Transfer success at work home, from private life to public life, and vice versa. Learn to evaluate the merits of effective strategies regardless of specific circumstances.
Like a recipe for macaroons or rules for crossing the street, the strategies can be used by everyone. A necessary condition for personal success is the ability to find strategies that best suit you in your personal experience or in the experience of other people. And discard those strategies that are not effective enough to achieve your current goals.
The ability to use models to change strategies is the essence of so-called accelerated learning. We can significantly speed up the usually rather sluggish learning process by applying our own effective strategies. We can also use the experience of others. Although, of course, one cannot expect to immediately reach their level. Each of us has the ability to learn to use both sides of our brain, to use our internal resources more effectively, and thus achieve exceptional success.
Part five
Creative approach to problem solving
Chapter 13
Using both hemispheres of the brain to think
Stages of the thinking process
Considering the stages of thinking can be very helpful. These stages do not have to be strictly sequential, but it is important for us to know how the various "operating" systems of the brain operate and how individual thinking processes relate to universal mental strategies.
Preparation
The preparation stage corresponds to the planning stage of a project and includes defining the problem, collecting data, and making basic assumptions. This strategy is in many ways similar to the first stage of the four-part cyclical success model we discussed in part one, in which you decide what you actually need and what your goal is. At this stage, you should formulate your goal in writing, and then use visualization techniques in order to experience the desired result as fully as possible and reflect it in the goal statement.
We have already talked about how important it is to have a clear idea of the desired outcome in the communication process. The same is true for the problem-solving process. Ask yourself the question: “What exactly would I like to achieve?” The essence of the communication “problem,” just like any other, is to bridge the gap between your current and desired state (by exchanging information, persuasion, getting answers to questions, etc.)
Analysis
At this stage, you should look deep into the problem, take into account all the pros, weigh all the pros and cons. Unfortunately, quite often solving a problem is reduced to analyzing its parts and working on them. The analysis of certain aspects of an issue, to the detriment of a holistic view, is associated with the activity of the left hemisphere of the brain. This process is linear in nature, the logical diagram looks something like this: “If A, then B.”
Unfortunately, the further you move along this path, the more difficult it becomes for you to accept the validity of any other, non-linear type of thinking. The advantage of the linear type of thinking is that on its basis it is possible to create algorithms used in the development of various kinds of methods and systems. The disadvantage of this type of thinking is that with its help it is impossible to solve problems that various logically constructed “systems” and computer programs are powerless to solve. Such problems are too complex and largely depend on the “human” factor.
Enthalpy (H) is a function of state, the increment of which is equal to the heat received by the system in an isobaric process.
Thermodynamic work and the amount of heat are not functions of state, since their value is determined by the type of process as a result of which the system changed its state.
The internal energy of a body can change only as a result of its interaction with other bodies. There are two ways to change internal energy: heat transfer and mechanical work (for example, heating during friction or compression, cooling during expansion).
Heat transfer is a change in internal energy without doing work: energy is transferred from more heated bodies to less heated ones. Heat transfer is of three types: thermal conductivity (direct exchange of energy between chaotically moving particles of interacting bodies or parts of the same body); convection (transfer of energy by flows of liquid or gas) and radiation (transfer of energy by electromagnetic waves). The measure of transferred energy during heat transfer is the quantity of heat (Q)
Work (W) is one of the forms of energy exchange (along with heat) of a thermodynamic system (physical body) with surrounding bodies; quantitative characteristics of energy conversion in physical processes depend on the type of process; The work of a system is positive if it gives out energy, and negative if it receives.
Types of thermodynamic systems:
1. An isolated system is a system that does not exchange either matter or energy with the environment (∆m=0, ∆E=0)
2. A closed system is a system that does not exchange matter with the environment, but can exchange energy (∆m=0, ∆E≠0)
3. An open system is a system that can exchange both matter and energy with the environment (∆m≠0, ∆E≠0) - example: living cell
The transition of a system from one state to another is called a process.
Types of thermodynamic processes:
· isobaric, p =const; for example, heating sand, water or stones under the influence of sunlight;
· isochoric, V =const, for example, souring milk in a glass bottle;
· isothermal, T =const, for example, inflating a balloon;
· adiabatic, when there is no release or absorption of heat, i.e. Δ Q=0, for example heating and cooling of air masses.
Standard condition- in thermochemistry, the state of a substance in which it is found at a temperature of 298.15 K and a pressure of 101.325 kPa (760 mm Hg)
2. The first law of thermodynamics. Enthalpy. The standard enthalpy of formation of a substance, the standard enthalpy of combustion of a substance. Standard enthalpy of reaction. Hess's law. Application of the first law of thermodynamics to biosystems.
The first law of thermodynamics provides a rigorous quantitative basis for analyzing the energy of various systems. To formulate it, it is necessary to introduce the following concepts:
Under condition understand the set of properties of a system that make it possible to define the system from the point of view of thermodynamics.
The state of the system is called equilibrium, if all properties remain constant for an arbitrarily long period of time and there are no flows of matter and energy in the system.
If the properties of a system are constant in time, but there are flows of matter and energy, the state is called stationary.
If the properties of a system change over time, the state is called transitional.
The change in the internal energy of the system ∆E is due to the work W, which is performed during the interaction of the system with the environment, and the transfer of heat Q between the environment and the system. The relationship between these quantities constitutes the content of the 1st law of thermodynamics:
The increment in the internal energy of the system ∆E in a certain process is equal to the heat Q received by the system, plus the work W done on the system in this process: ∆E=Q+W (all quantities are measured in Joules)
Enthalpy is a function of state, the increment of which is equal to the heat received by the system in an isobaric process (H=E+pV, where p is pressure and V is the volume of the system). The change in enthalpy (or the thermal effect of a chemical reaction) does not depend on the path of the process, being determined only by the initial and final state of the system. If the system somehow returns to its original state (circular process), then the change in any of its parameters, which is a function of the state, is equal to zero, hence Δ H = 0
The enthalpy of formation of compound A is the change in enthalpy of the system ∆H A that accompanies the formation of 1 mole of compound A from simple substances.
Standard enthalpy of combustion - Δ H hor o, the thermal effect of the combustion reaction of one mole of a substance in oxygen to the formation of oxides in the highest oxidation state. The heat of combustion of non-combustible substances is assumed to be zero.
