Intensive Properties: Features And Examples

The intensive properties is a set of properties of substances that do not depend on the size or amount of the substance considered. On the contrary, the extensive properties are related to the size or quantity of the substance considered.

Variables such as length, volume, and mass are examples of fundamental quantities, which are typical of extensive properties. Most of the other variables are deduced quantities, being expressed as a mathematical combination of the fundamental quantities.

An example of a deduced quantity is density: the mass of the substance per unit volume. Density is an example of an intensive property, so it can be said that intensive properties, in general, are deduced quantities.

The characteristic intensive properties are those that allow the identification of a substance by a certain specific value of them, for example the boiling point and the specific heat of the substance.

There are general intensive properties that can be common to many substances, for example color. Many substances can share the same color, so it is not useful to identify them; although it can be part of a set of characteristics of a substance or material.

Characteristics of intensive properties

Intensive properties are those that do not depend on the mass or size of a substance or material. Each of the parts of the system has the same value for each of the intensive properties. Furthermore, the intensive properties, for the reasons stated, are not additive.

If an extensive property of a substance such as mass is divided by another extensive property of it such as volume, an intensive property called density will be obtained.

Speed ​​(x / t) is an intensive property of matter , resulting from dividing an extensive property of matter such as the space traveled (x) between another extensive property of matter such as time (t).

On the contrary, if you multiply an intensive property of a body, such as the velocity by the mass of the body (extensive property), you will obtain the momentum of the body (mv), which is an extensive property.

The list of intensive properties of substances is extensive, including: temperature, pressure, specific volume, velocity, boiling point, melting point, viscosity, hardness, concentration, solubility, odor, color, taste, conductivity, elasticity, surface tension, specific heat, etc.

Examples

Temperature

It is a quantity that measures the thermal level or heat that a body possesses. Every substance is formed by an aggregate of dynamic molecules or atoms, that is, they are constantly moving and vibrating.

In doing so, they produce a certain amount of energy: heat energy. The sum of the caloric energies of a substance is called thermal energy.

Temperature is a measure of the average thermal energy of a body. Temperature can be measured based on the property of bodies to expand as a function of their amount of heat or thermal energy. The most used temperature scales are: Celsius, Fahrenheit and Kelvin.

The Celsius scale is divided into 100 degrees, the range comprised by the freezing point of water (0 ° C) and its boiling point (100 ° C).

The Fahrenheit scale takes the points mentioned as 32ºF and 212ºF, respectively. Y The Kelvin scale starts by establishing the temperature of -273.15 ºC as absolute zero (0 K).

Specific volume

Specific volume is defined as the volume occupied by a unit of mass. It is an inverse magnitude to the density; for example, the specific volume of water at 20 ° C is 0.001002 m 3 / kg.

Density

It refers to how much a certain volume occupied by certain substances weighs; that is, the m / v ratio. The density of a body is usually expressed in g / cm 3 .

The following are examples of the densities of some elements, molecules or substances: -Air (1.29 x 10 -3 g / cm 3 )

-Aluminum (2.7 g / cm 3 )

-Benzene (0.879 g / cm 3 )

-Copper (8.92 g / cm 3 )

-Water (1 g / cm 3 )

-Gold (19.3 g / cm 3 )

– Mercury (13.6 g / cm 3 ).

Note that gold is the heaviest, while air is the lightest. This means that a gold cube is much heavier than one hypothetically formed by only air.

Specific heat

It is defined as the amount of heat required to raise the temperature of a unit of mass by 1 ºC.

The specific heat is obtained by applying the following formula: c = Q / m.Δt. Where c is specific heat, Q is the amount of heat, m is the mass of the body, and Δt is the change in temperature. The higher the specific heat of a material, the more energy must be supplied to heat it.

As an example of specific heat values ​​we have the following, expressed in J / Kg.ºC and

cal / g.ºC, respectively:

-At 900 and 0.215

-Cu 387 and 0.092

-Fe 448 and 0.107

-H 2 O 4.184 and 1.00

As can be deduced from the specific heat values ​​listed, water has one of the highest known specific heat values. This is explained by the hydrogen bonds that form between water molecules, which have a high energy content.

The high specific heat of water is of vital importance in regulating the environmental temperature on earth. Without this property, summers and winters would have more extreme temperatures. This is also important in regulating body temperature.

Solubility

Solubility is an intensive property that indicates the maximum amount of a solute that can be incorporated into a solvent to form a solution.

A substance can dissolve without reacting with the solvent. The intermolecular or interionic attraction between the particles of the pure solute must be overcome for the solute to dissolve. This process requires energy (endothermic).

Furthermore, the energy supply is required to separate the solvent molecules, and thus incorporate the solute molecules. However, energy is released as the solute molecules interact with the solvent, making the overall process exothermic.

This fact increases the disorder of the solvent molecules, which causes the dissolution process of the solute molecules in the solvent to be exothermic.

The following are examples of the solubility of some compounds in water at 20 ° C, expressed in grams of solute / 100 grams of water:

-NaCl, 36.0

-KCl, 34.0

-NaNO 3 , 88

-KCl, 7.4

-AgNO 3 222.0

-C 12 H 22 O 11 (sucrose) 203.9

General features

Salts, in general, increase their solubility in water as the temperature increases. However, NaCl hardly increases its solubility with an increase in temperature. On the other hand, Na 2 SO 4 increases its solubility in water until reaching 30 ºC; from this temperature its solubility decreases.

In addition to the solubility of a solid solute in water, numerous situations can arise for solubility; for example: solubility of a gas in a liquid, of a liquid in a liquid, of a gas in a gas, etc.

Refractive index

It is an intensive property related to the change of direction (refraction) that a ray of light experiences when passing, for example from air to water. The change in direction of the light beam is due to the speed of light being greater in air than in water.

The refractive index is obtained by applying the formula:

η = c / ν

η represents the refractive index, c represents the speed of light in a vacuum, and ν is the speed of light in the medium whose refractive index is being determined.

The refractive index of air is 1,0002926, and of water 1,330. These values ​​indicate that the speed of light is greater in air than in water.

Boiling point

Is the temperature at which a substance changes state, from the liquid state to the gaseous state . In the case of water, the boiling point is around 100ºC.

Melting point

It is the critical temperature at which a substance passes from the solid state to the liquid state. If the melting point is taken as equal to the freezing point, it is the temperature at which the change from liquid to solid state begins. In the case of water, the melting point is close to 0 ºC.

Color, smell and taste

They are intensive properties related to the stimulation that a substance produces in the senses of sight, smell or taste.

The color of one leaf on a tree is the same (ideally) as the color of all the leaves on that tree. Also, the smell of a perfume sample is equal to the smell of the entire bottle.

If you suck on a slice of an orange, you will experience the same taste as eating the whole orange.

Concentration

It is the quotient between the mass of a solute in a solution and the volume of the solution.

C = M / V

C = concentration.

M = mass of solute

V = volume of solution

The concentration is usually expressed in many ways, for example: g / L, mg / ml,% m / v,% m / m, mol / L, mol / kg of water, meq / L, etc.

Other intensive properties

Some additional examples are: viscosity, surface tension, viscosity, pressure, and hardness.

Themes of interest

Qualitative properties .

Quantitative properties .

General properties ..

Properties of matter .

References

  1. Lumen Boundless Chemistry. (sf). Physical and Chemical Properties of Matter. Recovered from: courses.lumenlearning.com
  2. Wikipedia. (2018). Intensive and extensive properties. Recovered from: en.wikipedia.org
  3. Venemedia Communications. (2018). Definition of Temperature. Recovered from: conceptdefinition.de
  4. Whitten, Davis, Peck & Stanley. (2008). Chemistry. (8th ed.). CENGAGE Learning.
  5. Helmenstine, Anne Marie, Ph.D. (June 22, 2018). Intensive Property Definition and Examples. Recovered from: thoughtco.com

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