What Are Liquids & Forces Inside Liquids

 What Are Liquids & Forces Inside Liquids

What are Liquids

The term "liquid" can be used to describe both a substance's kind and its physical state. For instance, water is the most prevalent liquid on Earth.

A form of matter known as a liquid has unique characteristics that make it less stiff than a solid but more rigid than a gas. Unlike a solid, which has a defined shape, a liquid can flow. In contrast, a liquid takes on the shape of the container it is kept in. A liquid does not expand to fill the container like a gas does, despite the fact that this is comparable to a gas. Water, oil, alcohol, and mercury are a few examples of liquids that can be found at room temperature, which is roughly 20 degrees Celsius or 68 degrees Fahrenheit. Liquids can differ greatly from one another. For instance, olive oil pours more slowly than vinegar because it is heavier and thicker and hence weights more.

Physical properties of liquids
Cohesion

The intermolecular forces that hold molecules together cause the molecular components of a liquid to attract one another to varying degrees. Surface tension, which is what keeps water in droplets together or allows a pin to float on the surface, is a sign of cohesion.

Adhesion

 Depending on the type of liquid and the other component, there can be variable degrees of attractive forces between them. This explains why water adheres to surfaces differently depending on their composition, such as glass versus plastic. Adhesion also explains capillary action, which is when liquid tends to rise slender tubes or other porous materials, such as when a nurse uses a small glass tube to draw blood from a patient.

Volume

Despite taking on the shape of its container, liquid retains a largely constant volume. Unless vaporization or evaporation is affecting the volume, a modest change in pressure or temperature may only slightly modify the volume.

Compressibility

 Liquids are held together by strong intermolecular forces in a manner similar to that of solids, resulting in a relatively incompressible substance—another characteristic that distinguishes liquids from gases.

Variability

A liquid doesn't have a set form. It behaves similarly to gas in that it molds itself to the shape of the container it is held in, but unlike gas, it does not expand to fill the container.

Flowability

One of a liquid's fundamental properties is its capacity to flow. Its viscosity, which changes according on molecular size and intermolecular interactions, determines how much it flows, though. Because of its greater molecular structure, motor oil, for instance, has a far higher viscosity than water. As a result, motor oil moves much more slowly than water.

Evaporation

A liquid's molecular components frequently clash with one another or the container because of how much movement they undergo. These collisions result in the transfer of energy between molecules. Intermolecular forces are mainly in charge of the physical properties of the substance. Surface tension can be broken when enough energy is delivered to the liquid's surface, leading to the liquid evaporating. 

Forces inside liquids

Most important forces are intermolecular forces. The compacted states of matter are caused by intermolecular forces. Intermolecular forces, which hold the particles that make up solids and liquids together, have an impact on a number of the physical characteristics of matter in these two forms.

Intermolecular Forces

A force that attracts the protons or positive parts of one molecule to the electrons or negative parts of another molecule is known as an intermolecular force. A substance's various physical and chemical properties are influenced by this force. The strength of an object's intermolecular forces determines its boiling point; the higher the intermolecular forces, the higher the boiling point. We can compare the intermolecular forces between different substances by comparing their boiling points. This is so that these intermolecular forces can be broken and the liquid can be transformed into vapour using the heat that the substance absorbs at its boiling point.

Between molecules that have hydrogen bound to a strongly electronegative atom, such as O, N, or F, hydrogen bonds are very potent dipole-dipole interactions. Van der Waals forces and hydrogen bonds are examples of electrostatic intermolecular forces. Intermolecular interactions, which hold molecules to one another in liquids and hold polyatomic ions together, are weaker than intramolecular interactions, which hold the atoms within molecules together. Intermolecular contacts alter to cause transitions from the solid to liquid or from the liquid to gas phases, but intramolecular interactions are unaffected. Dipole-dipole interactions, London dispersion forces (commonly referred to as van der Waals forces), and hydrogen bonds are the three main types of intermolecular interactions.

Factors affecting intermolecular forces

The following interactions affect intermolecular forces:

a) Dipole-Dipole Forces

Polar molecules are attracted to one another through dipole-dipole interactions. Due to variations in the electronegativity of the atoms involved in a covalent connection, polar molecules contain permanent dipoles. One molecule's partially positive portion will gravitate toward another molecule's partially negative component. Simply we say that these forces are present between polar molecules.

Example: In HCl molecules, dipole-dipole interactions take place. Chlorine obtains a partial negative charge because it is relative more electronegative than hydrogen (whereas hydrogen acquires a partial positive charge). The HCl molecules then engage in a dipole-dipole interaction.

 b) Dipole Induced Dipole Forces or Debye Forces

Ion-induced dipole interactions are comparable to these interactions. The key distinction is that non-polar molecules are converted into induced dipoles by the proximity of polar molecules. Present between polar or permanent dipole and non-polar molecules, for example mixture of Ne and HCL

c) London Dispersion Forces or Instantaneous Dipole-Induced Dipole Forces

Discovered by German Physicist Fritz London in 1930. It has a limited range of operation and is the weakest force. The flow of electrons causes this type of force, which produces transient positive and negative charged areas. These forces present between non polar molecules.

d) Interactions between Ion-Dipoles

With the exception of the fact that they happen between ions and polar molecules, these interactions are comparable to dipole-dipole interactions. For example: The polar H2O molecules are drawn to the sodium and chloride ions in the beaker when NaCl and water are combined there. The size of the dipole moment affects how strong this interaction is, size and charge of an ion; the size of the polar molecule

e) Dipole Interactions Induced by Ions

In this kind of interaction, an ion that is put close to a non-polar molecule causes it to become polarised. Once charged, the non-polar molecules exhibit induced dipole behaviour. Ion-induced dipole interaction is the name given to this interaction between an ion and an induced dipole.

f) Hydrogen Bonding

Intermolecular forces tend to be exceptionally strong in molecules having hydrogen atoms bound to electronegative atoms like O, N, and F (and to a much lesser extent Cl and S). These lead to boiling temperatures that are significantly higher than those found for compounds where London dispersion forces predominate. With regard to the covalent hydrides of elements in groups 14–17. Group 14 contains the heavier constituents of methane as well as a sequence of boiling temperatures that rise gradually with molar mass. Nonpolar molecules, for which London dispersion forces are the only intermolecular forces, are predicted to follow this pattern (boiling point increases with molecular mass). As opposed to what their molar weights would suggest, the hydrides of the lightest members of groups 15–17 have boiling points that are almost higher than 100°C. 

Intramolecular forces

Ionic bond

This bond is created when all of the valence electrons are completely transferred between the atoms. It is a kind of chemical connection that produces two ions with opposing charges. In ionic bonding, the nonmetal takes the lost electrons to form a negatively charged anion while the metal loses them to become a positively charged cation.

Covalent bond

Atoms that share a similar electronegativities—the affinity or desire for electrons—form a covalent connection. Both atoms share electrons in order to achieve octet configuration and become more stable because they have equivalent affinities for electrons and neither has a propensity to donate them.

When the electronegativity difference between the linked atoms is smaller than 0.5, a nonpolar covalent bond is created between the same atoms or atoms with extremely similar electronegativities.

When atoms with marginally differing electronegativities share electrons, a polar covalent link is created. Between 0.5 and 1.9 electronegativity are different between linked atoms.

HF, O-H in water, and hydrogen chloride are all example of polar covalent bonds.

Metallic bond

This kind of covalent bonding only happens between metal atoms, and it allows the valence electrons to freely travel around the crystal structure. This link is created by the attraction of the fixed positively charged metal ions and the moving electrons, often known as the "sea of electrons." Samples of pure elemental metals, like gold or aluminium, or alloys, like brass or bronze, include metallic bonds. Freely moving electrons oscillate and emit photons of light, which is what gives metals their reflecting quality. They also allow metals to efficiently conduct heat and energy.

Difference between Intermolecular and Intramolecular forces