The world around us, with all its wealth and diversity, lives according to laws that are easy enough to explain with the help of such sciences as physics and chemistry. And even the basis of the life of such a complex organism as a person is nothing but chemical phenomena and processes.
Definitions and Examples
An elementary example is a kettle set on fire. After some time, the water will begin to heat up, then boil. We will hear a characteristic hiss, steam streams will fly out of the neck of the kettle. Where did it come from, after all, it was not in the dishes initially! Yes, but water, at a certain temperature, begins to turn into gas, changes its physical state from liquid to gaseous. Those. it remained the same water, only now in the form of steam. This is a physical phenomenon.
And we will see chemical phenomena if we put a tea bag in boiling water. Water in a glass or other vessel will turn red-brown. A chemical reaction will occur: under the influence of heat, the tea leaves will begin to steam up, highlighting the color pigments and taste properties inherent in this plant. We will get a new substance - a drink with specific, qualitative characteristics peculiar only to it. If we add a few tablespoons of sugar there, it will dissolve (physical reaction), and tea will become sweet (chemical reaction). Thus, physical and chemical phenomena are often related and interdependent. For example, if the same tea bag is placed in cold water, the reaction will not occur, the tea leaves and water will not interact, and sugar will not be dissolved either.
Thus, chemical phenomena are those in which some substances turn into others (water into tea, water into syrup, firewood into ash, etc.) Otherwise, a chemical phenomenon is called a chemical reaction.
Physical phenomena are those in which the chemical composition of a substance remains the same, but the state of aggregation, body size, shape, etc., change. (deformed spring, water frozen in ice, tree branch, broken in half).
Conditions of occurrence and course
Whether chemical and physical phenomena occur, we can judge by some signs and changes that are observed in a particular body or substance. So, most chemical reactions are accompanied by the following "identification marks":
- as a result or during the course of such a precipitate;
- the color of the substance changes;
- gas can be released, for example, carbon monoxide during combustion;
- there is an absorption or, conversely, the release of heat;
- light emission is possible.
So that chemical phenomena are observed, i.e. reactions occurred, some conditions are necessary:
- reacting substances must be in contact, be in contact with each other (i.e. the same tea leaves must be poured into a mug with boiling water);
- it is better to grind the substances, then the reaction will proceed faster, the interaction will come sooner (granulated sugar will dissolve sooner, melt in hot water than lumpy)
- so that many reactions can occur, it is necessary to change the temperature regime of the reacting components by cooling or heating them to a certain temperature.
It is possible to observe the chemical phenomenon experimentally. But you can describe it on paper using the chemical equation ( chemical reaction equation ).
Some of these conditions also work for the occurrence of physical phenomena, for example, a change in temperature or direct contact between objects and bodies. Suppose, if you hit the nail head hard enough with a hammer, it can deform, lose its normal shape. But she will remain a nail head. Or, when you turn on the lamp in the network, the tungsten filament inside it will start to heat up and glow. However, the substance from which the thread is made will remain the same tungsten.
The description of physical processes and phenomena occurs through physical formulas, the solution of physical problems.