Often from many people who are discussing a particular process, one can hear the words: "This is physics!" or "This is chemistry!" Indeed, almost all phenomena in nature, in everyday life and in space, with which a person meets during his life, can be attributed to one of these sciences. It is interesting to understand how physical phenomena differ from chemical ones.
Science physics
Before answering the question of how physical phenomena differ from chemical ones, it is necessary to understand what objects and processes each of these sciences explores. Let's start with physics.
From the ancient Greek language the word "fisis" is translated as "nature". That is, physics is a science of nature that studies the properties of objects, their behavior under various conditions, and the transformation between their states. The purpose of physics is to determine the laws that govern the ongoing natural processes. For this science, it does not matter what the studied object consists of and what its chemical composition is; for it, it is only important how the object behaves if it is exposed to heat, mechanical force, pressure, and so on.
Physics is divided into a number of sections that study a certain narrower circle of phenomena, for example, optics, mechanics, thermodynamics, atomic physics, and so on. In addition, many independent sciences depend entirely on physics, for example, astronomy or geology.
Science chemistry
Unlike physics, chemistry is a science that studies the structure, composition and properties of matter, as well as its change as a result of chemical reactions. That is, the object of studying chemistry is the chemical composition and its change in the course of a certain process.
Chemistry, like physics, has many sections, each of which studies a certain class of chemicals, for example, organic and inorganic, bio- and electrochemistry. Research in medicine, biology, geology, and even astronomy is based on the achievements of this science.
It is interesting to note that chemistry, as a science, was not recognized by the ancient Greek philosophers because of its orientation to experiment, and also because of the pseudoscientific knowledge that surrounded it (recall that modern chemistry was "born" from alchemy). Only from the Renaissance and largely thanks to the work of the English chemist, physicist and philosopher Robert Boyle, chemistry began to be perceived as a full-fledged science.
Examples of physical phenomena
A huge number of examples can be cited that obey physical laws. For example, every student already knows the physical phenomenon in grade 5 — the movement of a car on a road. It doesn’t matter what this car consists of, where it takes energy to move from, it only matters that it moves in space (along the road) along a certain trajectory at a certain speed. Moreover, the processes of acceleration and braking of the car are also physical. The section of physics "Mechanics" is engaged in the movement of a car and other solids.
Another well-known example of physical phenomena is the melting of ice. Ice, being a solid state of water, at atmospheric pressure can exist for an arbitrarily long time at temperatures below 0 o C, but if the ambient temperature is increased by at least a fraction of a degree, or if heat is transferred directly to ice, for example, by taking it in your hand, then it will begin to melt. This process, which occurs with the absorption of heat and a change in the state of aggregation of matter, is an exclusively physical phenomenon.
Other examples of physical phenomena are the floating of bodies in liquids, the rotation of planets in their orbits, the electromagnetic radiation of bodies, the refraction of light when two different transparent media cross the border, the flight of a projectile, the dissolution of sugar in water, and others.
Examples of chemical phenomena
As mentioned above, any processes that occur with a change in the chemical composition of the bodies taking part in them are studied by chemistry. If we go back to the example of a car, we can say that the process of burning fuel in its engine is a vivid example of a chemical phenomenon, because as a result of it, hydrocarbons interacting with oxygen lead to the formation of completely different combustion products, the main of which are water and carbon dioxide .
Another striking example of this class of phenomena is the process of photosynthesis in green plants. Initially, they have water, carbon dioxide and sunlight, but after the photosynthesis is complete, the starting reagents are gone, and glucose and oxygen are formed in their place.
In the general case, we can say that any living organism is a real chemical reactor, since a huge number of conversion processes take place in it, for example, the breakdown of amino acids and the formation of new proteins from them, the conversion of hydrocarbons into energy for muscle fibers, the process of human breathing, in which hemoglobin binds oxygen, and many others.
One of the amazing examples of chemical phenomena in nature is recognized as the cold glow of fireflies, which is the result of the oxidation of a special substance - luciferin.
In the technical field, an example of chemical processes is the manufacture of dyes for clothing and food.
Differences
How are physical phenomena different from chemical ones? The answer to this question can be understood if we analyze the above information about the objects of study of physics and chemistry. The main difference between them is a change in the chemical composition of the object under consideration, the presence of which indicates transformations in it, while in the case of unchanged chemical properties of the body they speak of a physical phenomenon. It is important not to confuse the change in the chemical composition and the change in structure, which is understood as the spatial arrangement of the atoms and molecules that make up the body.
Reversibility of physical and irreversibility of chemical phenomena
In some sources, when answering the question of how physical phenomena differ from chemical ones, one can find information that physical phenomena are reversible and chemical ones are not, however, this is not entirely true.
The direction of any process can be determined using the laws of thermodynamics. These laws say that any process can go on spontaneously only if its Gibbs energy decreases (a decrease in internal energy and an increase in entropy). However, this process can always be reversed if an external energy source is used. For example, let’s say that recently scientists discovered the reverse process of photosynthesis, which is a chemical phenomenon.
Burning process
This issue has been specifically addressed in a separate paragraph, since many people consider burning a chemical phenomenon, but this is not true. However, to consider the combustion process as a physical phenomenon will also be wrong.
A common phenomenon of burning (a bonfire, fuel combustion in an engine, gas burner or burner, etc.) is a complex physical and chemical process. On the one hand, it is described by a chain of chemical oxidation reactions, but on the other hand, as a result of this process, strong thermal and light electromagnetic radiation occurs, and this is already a field of physics.
Where is the border between physics and chemistry?
Physics and chemistry are two different sciences that have different research methods, while physics can be both theoretical and practical, while chemistry is basically a practical science. However, in some areas, these sciences touch so close that the boundary between them is blurred. The following are examples of scientific fields in which it is difficult to determine "where physics is and where chemistry is":
- quantum mechanics;
- nuclear physics;
- crystallography;
- Materials Science;
- nanotechnology.
As can be seen from the list, physics and chemistry closely intersect when the phenomena under consideration have an atomic scale. Such processes are commonly called physicochemical. It is curious to note that the only person who received the Nobel Prize in chemistry and physics at the same time is Maria Skłodowska-Curie.