The Characteristics of liquids Serve to define the molecular structure and physical properties of one of the States of the material .
The most studied are compressibility, surface tension, cohesion, adhesion, viscosity , Freezing point and evaporation .
The liquid is one of the three states of aggregation of matter, the other two being solid and gaseous. There is a fourth state of matter, plasma, but only occurs under conditions of pressure and extreme temperatures.
Solids are substances that maintain their shape with which they can be easily identified as objects. Gases are substances that are floating in the air and dispersed in the air, but can be trapped in containers such as bubbles and balloons.
The liquids are in the middle of the solid state and the gaseous. Generally, by exerting changes in temperature and / or pressure, it is possible to pass a liquid to either of the other two states.
There are a lot of liquid substances present on our planet. Among them are oily fluids, organic and inorganic liquids, plastics and metals such as mercury. If you have types of molecules of different materials dissolved in a liquid is called solution, such as honey, body fluids, alcohol And physiological serum.
Main features of the liquid state
1- Compressibility
The limited space between its particles makes the liquid almost incompressible substance. That is, pressing down to force a certain amount of liquid into a very small space for its volume is very difficult.
Many automotive dampers or large trucks use pressurized liquids, such as oils, in sealed tubes. This helps to absorb and counteract the constant hustle that the track exerts on the wheels, seeking the least transmission of movement to the structure of the vehicle.
2- Changes of state
Exposing a liquid to high temperatures would make it evaporate. This critical point is called a boiling point and is different depending on the substance. Heat increases the separation between the molecules of the liquid until they separate sufficiently to disperse as a gas.
Examples: water evaporates at 100 ° C, milk at 100.17 ° C, alcohol at 78 ° C and mercury at 357 ° C.
In the opposite case, exposing a liquid to very low temperatures would make it solidify. This is called freezing point and will also depend on the density of each substance. The cold slows the movement of atoms by increasing their intermolecular attraction enough to harden into solid state.
Examples: water is frozen at 0 ° C, milk between -0.513 ° C and -0.565 ° C, alcohol at -114 ° C and mercury at approximately -39 ° C.
It should be noted that lowering the temperature of a gas until it is converted into liquid is called condensation, and heating a solid substance enough could be possible to melt or melt it in a liquid state. This process is called fusion. The water cycle perfectly explains all these processes of state changes.
3- Cohesion
It is the tendency of the same type of particles to attract each other. This intermolecular attraction in the liquids allows them to move and to flow maintaining together until they find the form to maximize this force of attraction.
Cohesion literally means"action of sticking together". Under the liquid surface, the cohesive force between molecules is the same in all directions. However on the surface the molecules only have this force of attraction towards the sides and especially towards the interior of the liquid body.
This property is responsible for the fact that liquids form spheres, which is the form that has the least surface area to maximize intermolecular attraction.
In conditions of zero gravity, the liquid would remain floating in a sphere, but when the sphere is attracted by gravity, they create the known form of gout in an effort to remain stuck.
You can appreciate the effect of this property with the drops on flat surfaces; Its particles are not dispersed by the cohesive force. Also in closed faucets with slow drips; The intermolecular attraction holds them together until they become very heavy, that is, when the weight exceeds the cohesive force of the liquid it simply falls.
4- Surface tension
The cohesive force on the surface is responsible for the creation of a thin layer of particles much more attracted to each other than to the different particles around them, such as air.
The molecules of the liquid will always seek to minimize the surface area by drawing inwards, giving the sensation of having a protective skin.
As long as this attraction is not disturbed, the surface can be incredibly strong. This surface tension allows, in the case of water, certain insects to slide and remain on the liquid without sinking.
It is possible to keep flat solid objects on liquid if it is sought to disturb as little as possible the attraction of surface molecules. It is achieved by distributing the weight along the length and width of the object in order not to exceed the cohesive force.
The cohesive force and surface tension are different depending on the type of liquid and its density.
5- Accession
It is the force of attraction between different types of particles; As its name implies, literally means"action of adhering." In this case, liquid containers and the areas where they flow are generally present on the walls of the containers.
This property is responsible for liquids wetting solids. It occurs when the adhesion force between the liquid molecules and the solid is greater than the intermolecular cohesion force of the pure liquid.
Capillarity
The adhesion force is responsible for the liquids to rise or fall when interacting physically with a solid. This capillary action can be evidenced in the solid walls of the containers, since the liquid tends to form a curve called meniscus.
Higher adhesion strength and lower cohesive strength, the meniscus is concave and if not, the meniscus is convex. The water will always form an upward curve where it makes contact with a wall and the mercury will form a downward curve; Behavior that is almost unique in this material.
This property explains why many liquids rise when they interact with very narrow hollow objects like pitillos or tubes. The narrower the diameter of the cylinder, the force of adhesion to its walls will cause the liquid to enter almost immediately into the container, even against the force of gravity.
7- Viscosity
It is the internal force or resistance to deforming that a liquid offers when it flows freely. It depends mainly on the mass of the internal molecules and the intermolecular connection that attracts them. Slower flowing liquids are said to be more viscous than fluids that flow easier and faster.
For example: motor oil is more viscous than gasoline, honey is more viscous than water and maple syrup is more viscous than vegetable oil.
For a liquid to flow it needs the application of a force; For example gravity. But you can reduce the viscosity of the substances by applying heat. The temperature rise causes the particles to move faster allowing the liquid to flow easier.
More information on liquids
As in the particles of solids, those of liquids are subject to a permanent intermolecular attraction. However, in liquids there is more space between molecules, this allows you to move and flow without staying in a fixed position.
This attraction maintains the volume of the liquid constant, enough to keep the molecules bound by gravity without dispersing in the air as in the case of the gases, but not enough to keep it in a form defined as in the Case of solids.
In this way, a liquid will seek to flow and slide from high levels to encompass the lowest portion of a container thus taking the shape of the container, but without changing its volume. The surface of liquids is usually flat thanks to the gravity that presses the molecules.
All of these descriptions mentioned above are present every day when test tubes, plates, cups, flasks, bottles, vases, tanks, tanks, wells, aquariums, piping systems, rivers, lakes and dams are filled with water.
Curious facts about water
He Water Is the most common and abundant liquid of the earth, and is one of the few substances that can be found in any of the three states: the solid in the form of ice, its normal liquid state and the gaseous in the form of water vapor.
- It is the non-metallic liquid with the most cohesive force.
- It is the common liquid with greater surface tension excepting the mercury.
- Most solids expand as they melt. Water expands upon freezing.
- Many solids are denser than their corresponding liquid states. Ice is less dense than water, which is why it floats.
- It is an excellent solvent. It is called the universal solvent
References
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- Michael Blaber (1996). Properties of Liquids: Viscosity and Surface Tension - Intermolecular Forces. Florida State University - Dept of Biomedical Sciences. Retrieved from mikeblaber.org.
- Chemical Education Division Groups. Properties of Liquids. Bodner research Web. Purdue University - College of Science. Retrieved from chemed.chem.purdue.edu.
- Liquid Basics. Andrew Rader Studios. Retrieved from chem4kids.com.
- Properties of Liquids. Department of Chemistry & Biochemistry. Florida State University, Tallahassee. Retrieved from chem.fsu.edu.
- Encyclopedia of Examples (2017). Examples of Solid, Liquid and Gaseous. Retrieved from examples.co.