Matter is everything that surrounds us. Intensive and extensive properties refers to the classification of properties according to their dependence on the amount of matter . Let’s see each one separately.
Definition of intensive properties
Are those properties that do not depend on the quantity or size of the material . They are also known as intrinsic or local properties.
Imagine that we have a system with an X property. If we divide the system into parts A, B, and C, the property X of A is equal to the property X of B and C:
Key to remember if a property is intensive : ownership of the parts is equal to the ownership of the system.
Examples of intensive properties
Below, we present some of the best known intensive properties.
Temperature is the measure of the average kinetic energy of atoms. The Celsius scale, or centigrade, is the most widely used scale worldwide to measure temperature.
It is an intensive property because if we measure the temperature of a liter of water or a glass of water in the same conditions, the measurement will be the same.
2. Melting point
The melting point is the temperature at which a solid phase compound passes into its liquid phase. In the international system, the unit is the Kelvin (K). It can also be expressed in degrees centigrade.
It is an intensive property because it does not depend on the amount of material. The temperature at which a gram of a substance melts will be equal to the temperature that a kilogram of the same substance melts.
3. Boiling point
The boiling point is the temperature at which a compound in the liquid phase passes into its gas phase. The typical example is that of water, which boils and transforms into steam at 100ºC when the atmospheric pressure is equal to 1 atmosphere.
For example, distillation is a technique that takes advantage of the difference in the boiling points of the compounds to be able to separate them, as in the case of alcohol and water.
Elasticity is a measure of how much an object can be deformed when a certain force is applied to it. Materials like rubber have a greater elastic property.
It is an intensive property because a rubber meter has the same elasticity as 10 centimeters of rubber.
Density is the ratio between the mass of a body or material and the volume it occupies. It is calculated by dividing the amount of mass in grams by volume in milliliters.
It is an intensive property because the density does not vary whether we measure it in a kilogram of matter, or in two tons of it.
Viscosity is the property of fluids to resist flow. The more viscous a fluid is, the thicker it will be. The viscosity in the fluids generally decreases with the increase in temperature.
Viscosity is measured in newtons-seconds per square meter (Ns / m 2 ). Another unit commonly used for viscosity is the poise (P), where 10 P equals 1 Ns / m 2
The viscosity of the honey at a certain temperature is the same regardless of its quantity.
7. Surface tension
The surface tension is the property of the liquids to resist the forces that are applied on their surface. This property is the result of the forces that hold together the molecules of the liquid on the surface.
It is an intensive property because the intermolecular forces are equal over the entire surface of the fluid.
8. Specific heat
Specific heat is an intensive property that describes how much heat is needed to increase the temperature of a unit of mass of a material. In the international system, the specific heat unit is Joules per kilogram Celsius (J / kg ºC).
The specific heat of water (4186 J / kg ºC) is five times greater than that of glass (840 J / kg ºC). This means that five times more heat is required to increase the temperature of one kilogram of water than one kilogram of glass.
Resistivity is the property of a material to resist the flow of electric charges, regardless of its size or shape. In the international system the unit for resistivity is ohm meter (Ω · m)
10. Thermal conductivity
Thermal conductivity is the ability of materials to transfer heat. In the international system of units is measured in watts per meter and kelvin (W / mk)
Ice melts faster on copper foil because of its high thermal conductivity.
Definition of extensive properties
Are those properties that depend on the size of the system . In this case, if we divide a system into parts A, B and C, then the ownership of the system will be equal to or greater than the sum of the parts:
Key to remember if a property is extensive: ownership of the parts adds to the ownership of the system.
Example of extensive properties
Below are some extensive properties.
The length is a physical measure of distance: the separation between two objects, the space that an object moves, the length of a cable and other measures depend on the distance. The unit of the international system for the length is the meter.
It is an extensive property because it depends on the size: if we cut a ten-meter string into pieces of a meter, the length of the final pieces is not equal to the original.
Mass is the amount of matter that an object contains. Mass, unlike weight, does not depend on gravity. The unit of the international system for the mass is the kilogram.
It is an extensive property because by removing a piece of material that is being measured, the final mass measurement changes.
Volume is the measure of the three-dimensional space that an object occupies. In the international system, the unit of volume is the cubic meter (m 3 ). The liter is also used. The volume of a solid can be measured by the volume of liquid that it can displace when it is completely submerged.
It is an extensive property because when adding more material to a container the volume changes, even if it is the same material.
The volume of the liquid in the two cups changes.
14. Number of molecules
The number of molecules in a material varies depending on the amount of the material. We know that one mole of a substance has 602,000,000,000,000,000,000,000 molecules, in scientific notation it would be 6.02×10 23 , this number is also known as Avogadro’s number .
It is an extensive property because the number of molecules increases or decreases depending on whether there is more or less material.
Inertia is the property of bodies to resist changes in movement or rest. It is a property associated with the mass, while more mass, more inertia.
The books on the chair that moves, continue by inertia its movement when it hits the chair on the wall.
16. Heat capacity
The heat capacity is the amount of heat needed to change the temperature of a substance. In the international system the unit of heat capacity is joules per kelvin (J / K).
It is an extensive property, since it depends on the amount of substance, in addition to the temperature and pressure. To heat 10 liters of water requires more heat than to heat a cup of water.
Enthalpy is the amount of energy that a system gives or absorbs around it. In the international system the enthalpy unit is joules (J).
The reaction of rubidium with water releases a large amount of heat.
Entropy is the measure of the disorder of a system. In the international system, the entropy unit is joules per kelvin (J / K).
It is an extensive property because the larger the system, the greater the disorder.
The tendency in the nature of the systems is the disorder
19. Electric charge
Electric charge is a property that produces forces that can attract or repel matter. In the international system, the load unit is the Coulomb (C), which represents 6.242×10 18 e , where e is the proton charge. The load can be positive or negative.
Resistance is the electrical property that prevents the passage of current. In the international system, the resistance unit is measured in Ohm. The resistance of an object depends on its shape and length.