EXTENSIVE PROPERTIES: FEATURES AND EXAMPLES - CHEMISTRY - 2025

The extensive properties are those that depend on the size or the portion of the subject under consideration. Meanwhile, the intensive properties are independent of the size of the matter; therefore, they do not change when you add material.

Among the most emblematic extensive properties are mass and volume, since when the amount of material to be considered is modified, they vary. Like other physical properties, they can be analyzed without a chemical change.

Some of the most considerable extensive properties.

The measurement of a physical property can change the arrangement of matter in a sample, but not the structure of its molecules.

Likewise, extensive quantities are additive, that is, they can be added. If a physical system formed by several parts is considered, the value of an extensive magnitude in the system will be the sum of the value of the extensive magnitude in the different parts of it.

Examples of extensive properties are: weight, force, length, volume, mass, heat, power, electrical resistance, inertia, potential energy, kinetic energy, internal energy, enthalpy, Gibbs free energy, entropy, constant volume heat capacity, or constant pressure heat capacity.

Note that extensive properties are in common use in thermodynamic studies. However, when determining the identity of a substance, they are not very helpful, since 1g of X is not physically different from 1g of Y. To differentiate them, it is necessary to rely on the intensive properties of both X and Y.

Characteristics of extensive properties

They are additive

An extensive property is additive to its parts or subsystems. A system or material can be divided into subsystems or parts and the extensive property considered can be measured in each of the indicated entities.

The value of the extensive property of the complete system or material is the sum of the value of the extensive property of the parts.

However, Redlich pointed out that the assignment of a property as intensive or extensive may depend on the way the subsystems are organized and if there is interaction between them.

Therefore, indicating the value of an extensive property of a system as a sum of the value of the extensive property in the subsystems can be a simplification.

Source: Pxhere

Mathematical relationship between them

Variables like length, volume, and mass are examples of fundamental quantities, which are extensive properties. Amounts deducted are variables that are expressed as a combination of amounts deducted.

If a fundamental quantity such as the mass of a solute in a solution is divided by another fundamental quantity, such as the volume of the solution, a deduced quantity is obtained: the concentration, which is an intensive property.

In general, if an extensive property is divided by another extensive property, an intensive property is obtained. Whereas if an extensive property is multiplied by an extensive property, an extensive property is obtained.

This is the case of potential energy, which is an extensive property, it is the product of the multiplication of three extensive properties: mass, gravity (force) and height.

An extensive property is a property that changes as the amount of matter changes. If matter is added there is an increase in two extensive properties such as mass and volume.

Examples

Mass

It is an extensive property that is a measure of the amount of matter in a sample of any material. The greater the mass, the greater the force required to set it in motion.

From a molecular point of view, the greater the mass, the greater the cluster of particles that physical forces experience.

Mass and weight

The mass of a body is the same anywhere on Earth; while its weight is a measure of the force of gravity and varies with distance from the center of the Earth. Since the mass of a body does not vary with its position, mass is a more fundamental extensive property than its weight.

The fundamental unit of mass in the SI system is the kilogram (kg). The kilogram is defined as the mass of a platinum-iridium cylinder stored in a vault at Sevres, near Paris.

1000 g = 1 kg

1000 mg = 1 g

1000000 μg = 1 g

Length

It is an extensive property that is defined as the dimension of a line or a body considering its extension in a straight line.

Length is also defined as the physical magnitude that allows marking the distance that separates two points in space, which can be measured, according to the International System, with the unit meter.

Volume

It is an extensive property that indicates the space that a body or material occupies. In the metric system, volumes are usually measured in liters or milliliters.

1 liter equals 1,000 cm ³. 1 ml is 1cm ³. In the International System, the fundamental unit is the cubic meter, and the cubic decimeter replaces the Metric Unit the liter; that is, a dm ³ equals 1 L.

Force

It is the ability to perform physical work or movement, as well as the power to support a body or resist a push. This extensive property has clear effects for large quantities of molecules, since considering individual molecules, they are never still; they always move and vibrate.

There are two types of forces: those that act in contact and those that act at a distance.

The Newton is the unit of force, defined as the force applied to a body with a mass of 1 kilogram, communicating an acceleration of 1 meter per second squared.

Energy

It is the ability of matter to produce work in the form of movement, light, heat, etc. Mechanical energy is the combination of kinetic energy and potential energy.

In classical mechanics it is said that a body does work when it alters the state of motion of a body.

Molecules or any type of particle always have associated energy levels and are capable of carrying out work with the appropriate stimuli.

Kinetic energy

It is the energy associated with the movement of an object or particle. The particles, although they are very small and therefore have little mass, travel at speeds that border on that of light. As it depends on the mass (1 / 2mV ²), it is considered an extensive property.

The kinetic energy of a system at any instant of time is the simple sum of the kinetic energies of all the masses present in the system, including the rotational kinetic energy.

An example is the solar system. At its center of mass the sun is almost stationary, but the planets and planetoids are in motion around it. This system served as the inspiration for Bohr's planetary model, in which the nucleus represented the sun and the electrons the planets.

Potential energy

Regardless of the force that originates it, the potential energy that a physical system possesses represents the energy stored by virtue of its position. Within a chemical system, each molecule has its own potential energy, so it is necessary to consider an average value.

The notion of potential energy is related to the forces that act on the system to move it from one position to another in space.

An example of potential energy is in the fact that an ice cube hits the ground with less energy compared to a solid block of ice; Furthermore, the force of the impact also depends on the height where the bodies are thrown (distance).

Elastic potential energy

As a spring is stretched, it is observed that more effort is required to increase the degree of stretch of the spring. This is because a force is generated within the spring that opposes the deformation of the spring and tends to return it to its original shape.

It is said that potential energy (elastic potential energy) accumulates within the spring.

Hot

Heat is a form of energy that always flows spontaneously from bodies with higher caloric content to bodies with lower caloric content; that is, from the hottest to the coldest.

Heat is not an entity as such, what exists is heat transfer, from places with higher temperatures to places with lower temperatures.

The molecules that make up a system vibrate, rotate and move, giving rise to an average kinetic energy. Temperature is proportional to the average speed of the moving molecules.

The amount of heat transferred is usually expressed in Joule, and it is also expressed in calories. There is an equivalence between both units. One calorie equals 4,184 Joule.

Heat is an extensive property. However, specific heat is an intensive property, defined as the amount of heat it takes to raise the temperature of 1 gram of substance by one degree Celsius.

Thus, the specific heat varies for each substance. And what is the consequence? In the amount of energy and time it takes for the same volume of two substances to be heated.

Themes of interest

Qualitative properties.

Quantitative properties.

General properties.

Properties of matter.

References

1. Helmenstine, Anne Marie, Ph.D. (October 15, 2018). The Difference between Intensive and Extensive Properties. Recovered from: thoughtco.com
2. Texas Education Agency (TEA). (2018). Properties of Matter. Recovered from: texasgateway.org
3. Wikipedia. (2018). Intensive and extensive properties. Recovered from: en.wikipedia.org
4. CK-12 Foundation. (July 19, 2016). Extensive and Intensive Properties. Chemistry LibreTexts. Recovered from: chem.libretexts.org
5. The Editors of Encyclopaedia Britannica. (July 10, 2017). Kinetic energy. Encyclopædia Britannica. Recovered from: britannica.com