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There are many characteristics of matter that we can measure, including physical and chemical properties. The essential difference between the two is that the physical properties of matter can be measured without changing its atomic structure, while the chemical properties can only be observed when there is a change in its atomic structure . In order to determine which characteristics correspond to the physical and chemical characteristics of a compound, one must first pay attention to the changes that occur (or not) in it.
physical properties
It should be noted that in order to know the physical properties of a compound it is not necessary to change its composition at all. It can be measured and observed without affecting it, so its chemical formula does not change. Some of these aspects are, for example, color, molecular weight and volume. Some examples of physical properties of matter are: electrical resistance, boiling point, density, mass, and volume.
Below we explain some physical properties in some detail:
electrical resistance
Determine how hard it is for electric current to flow through the material in question. Aluminum, copper, and silver are known to have low electrical resistance, so they allow a lot of electrical current to flow. On the other hand, wood, rubber and glass have high resistance to electric current and for this reason they are used as insulating and safety materials in various environments with the presence of electricity.
Temperature
It determines how much the system in question is internally agitated. This means that the molecules of a compound move abruptly when the heat falls on them; It always depends on the intensity of such a temperature . The most commonly used temperature scales are degrees Fahrenheit, Celsius, and Kelvin. The tool used to measure temperature is the thermometer and it comes in various forms.
The density
It is one of the physical characteristics that tend to arouse the greatest interest in elements and bodies. It is defined as the ratio of its volume to its mass. Let us consider that lead has a density of 11.3 g/cm3; while aluminum, known for being a resistant and light material, has a density of 2.70 g/cm3.
boiling point
It refers to the temperature necessary for a substance to change from the liquid state of matter to the gaseous state. There is also the melting point, which is the temperature at which solids become a liquid.
chemical properties
Knowing the chemical properties of a compound requires a totally different methodology from the one used to see the physical properties. The chemistry of an element can only be observed when some kind of change occurs in the chemical structure of its compounds; in this case, its formula would change.
It proceeds by subjecting the compound to be part of a reaction. For this, it is combined with another compound or elements and may also be subjected to different conditions of temperature, pressure, etc. The reactions also help determine how the compound will react in the future. This result is part of what will describe the chemical properties of the compound.
Some examples of chemical properties are as follows:
reactivity
It is the ability of a substance to allow a reaction with another substance to occur. In the known universe, oxygen stands out as one of the most reactive elements, while neon is one of the least reactive.
heat of combustion
It is the energy that is released as a result of burning a substance. We know, for example, that the heat of combustion of carbon monoxide is -281.65 kJ/mol.
ionization
It is the property of an atom to form ions, an electrical charge by gaining or losing electrons. For example, mixing chlorine with sodium produces sodium chloride, which has positively charged ions (cations) in sodium and negatively charged ions (anions) in chlorine.
The affinity for electrons
This is the property of a molecule or an atom to gain electrons. For example, it is known that sodium has less affinity to gain electrons than chlorine.
signs of chemical change
At some level it is not necessary for a compound to actively undergo a chemical reaction in order to establish its chemical properties. In the previous list it can be seen that there are chemical properties that suppose, in addition to the reaction, conditions that will affect the substances in an observable way. This situation can be used to determine that the compound has changed with the naked eye.
At certain times the environmental conditions themselves can trigger chemical reactions. There are signs such as a change in color or temperature, the release of gases from the compound and the formation of new substances that are usually clearly visible. For example, when burning a piece of paper, smoke is released and ashes are formed, elements that were not there at the beginning. With these signs it is possible to establish with the naked eye that the compound has changed chemically.
References
- Web Chemistry (s/f). Chemical changes in matter . Available at: http://www.quimicaweb.net/grupo_trabajo_ccnn_2/tema6/index.htm
- Zita, A. (2021). Physical and chemical properties of matter . Available: https://www.diferenciador.com/propiedades-fisicas-y-quimicas-de-la-materia/
