Liquid

The Topic for collage is Liquid- Basic Concepts.

Middle of Collage

Kinetic view of matter is

.Solid hold shape and fixed volume

.Solids have definite volume definite shape high density and compressibility

.Liquid take shape of container ,free surface,fixed volume

.Liquids have high density,slightly compressible,flow readily

.Gas assume volume and shape of container ,Low density very compressible and free motion

.Measure of intermolecular forces is expressed in liquid properties in the form of boiling point,melting point ,∆ H vapourisation,∆ H sublimation , ∆ H fusion.

Left side of collage

There are in fact three basic types of interactions between molecules which are , in order of increasing strengths;

1. Dipole dipole interactions.

2. Ion Dipole interaction .

3. Van der Waals interactions or dispersion forces

4. Hydrogen bonds

And these secondary secondary bonding interactions ,like primary bonding interactions, involve the electrons

Dipole dipole forces

Figure above shows A network of partial + and – charges attract molecule to each other

Covalent molecules are sometimes described as dipoles meaning that themolecule has two poles.One end (pole) of the molecule has partial positive charge while the other end has partial negative charge. The molecule will orient themselves so that the opposite charges attract principle operates effectively.

Dispersion forces: Temporary Forces that arise as a result of temporary dipoles induced in atoms or molecules(exist in all molecules)

Resulted from electron cloud distortion

Ion induced dipole interaction (Mg⁺² ion interacting with water dipoles )

Dipole induced dipole interaction

Bottom of Collage

H-Bonding special dipole dipole forces involving special atoms H,N,O and F

Hydrogen Bond is special dipole dipole interaction between H bond in polar N-H, H-F, O-H bond and electronegative O,N and F atom.

The hydrogen bond is really a special case of dipole forces. A hydrogen bond is the attractive force between the hydrogen attached to an electronegative atom of one molecule and an electronegative atoms of different molecule. Usually the electronegative atom is O ,N or F.

In other words- The hydrogen on one molecule attached to O or N that is attracted to an O or N of a different molecule.

Hydrogen bonding is usually stronger than normal dipole forces between molecules. Of course hydrogen bonding is not nearly as strong as normal covalent bonds within a molecule-it is only about 1/10 as strong.

Inter molecular 41KJ to vapourise 1 mole of water

Intera olecular 930 KJ to break all O-H bond in one mole of water.

Figures below show intra molecular H Bonding

Figure below show inter molecular H Bonding

Right side of collage

Many elements form compounds with hydrogen-referred to as hydrides

If we plot the boiling points of the hydrides of the group 4 elements (CH₄, SIH₄, GeH₄, SnH₄, PbH₄),you find that the boiling points increase as you go down the group.CH₄ has least boiling point while PbH₄ has highest boiling point.The increase in boiling point happens because the molecules are getting larger with more electrons,so vander Waals dispersion forces become greater

Evidence of hydrogen bonding

If we repeat this exercise with the hydrides of element in Groups 5,6 and 7, something odd happens.Plot of boiling points the hydrides of group 5,6,7^th are shown in collage are given in figure below.

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Although for the most part the trend is exactly the same ,the boiling point of the hydrides of the first element in each group is abnormally high.In the cases of NH₃(5^th), H₂O (6^th)and HF (7^th)there must be some additional intermolecular forces of attraction, requiring significantly more heat energy to break.These relatively powerful intermolecular forces are described as hydrogen bonds.

Properties Of Liquid:

Water molecules at the surface (next to the air) holds closely together ,forming an invisible film .We call this waters surface tension.surface tension is essential for the transfer of energy from wind to water to create waves are necessary for rapid oxygen diffusion in lakes and seas

Surface tension: J/m²: Stronger intermolecular forces, higher surface tension

Capillary action: cohesion(coh) is attraction between like molecules.

Adhesion(adh) is attraction between unlike molecules

Figure below shows Adh> coh there is capillary action.

Message

t`s wonderful to climb the liquid mountains of the sky. Behind me and before me is God and I have no fears.

- Helen Keller

References:

1.Chaplin, Mark. 2004. "Water Structure and Behavior." London South Bank University, London, England.

2.http://www.vias.org/genchem/kinetic_12450_08.html

3.https://www.learningpod.com/question/cohesion-and-adhesion-in-liquids-surface-tension-and-capillary-action-image-figure-a-shows/5a3752ff-c90a-4a7c-8eec-9943b19a5f7d