Not+just+Food+-+presentation

Helo my groupmates, u all remember to have a short presentation on coming week? shall we have a discussion here?

kindly post ur work done here (the info u have found). thankyou

there are 5 terms to be present, type of electrostatic force, DLVO theory, electrical double layer, Zeta potential, effect of inonic strength & pH.

well, i start with my part 1st, i m doing Zeta potential, waiting for u all post.

= Zeta potential =

· Scscientific term of eletrokinetic potential in a colloidal system.
 * ·Denoted as //ζ-potential//.
 * ·The potential difference between the dispersion medium and the stationery layer of fluid attached to the dispersed particle.
 * ·Zeta potential related to the stability of colloidal dispersion.
 * ·Zeta potential indicates the degree of repulsion between adjacent, similarly charged particle in the dispersion.
 * ·When the potential is low, attraction exceeds repulsion and the dispersion will break and coagulate. Considered as not stable.
 * ·When the potential is high, repulsion force is higher than attraction force, the dispersion is considerable stable.

Kok Ming.Why the words become weird??ist any problem with the page here? -by Siew Choo



Hui theng is here, i am doing electrical double layer part. I would like to share some information about electrical double layer.
 The Electric Double Layer
 * Development of a net charge at the particle surface affects the distribution of ions in the surrounding interfacial region, resulting in an increased concentration of counter ions (ions of opposite charge to that of the particle) close to the surface
 * Thus an electrical double layer exists round each particle
 * An electrical double layer exists around each particle.
 * The liquid layer surrounding the particle exists as two parts; an inner region (Stern layer) where the ions are strongly bound and an outer (diffuse) region where they are less firmly associated
 * Within this diffuse layer is a notional boundary known as the slipping plane, within which the particle acts as a single entity
 * The potential at this boundary is known as the zeta potential

Siew Choo here..

DLVO theory

The DLVO theory, named after the two Russian scientists (Derjaguin and Laudau) and the two Dutch scientists (Verwey and Overbeek) who developed it around the 1940’s, is a corner stone of colloid science. This can be written as:
 * This theory describes the forces present between charged surfaces interacting through a liquid medium.
 * It combines the effects of the London dispersion van der Waals attraction and the electrostatic repulsion due to the overlap of the double layer of counterions.
 * The central concept of the DLVO theory is that the total interaction energy of two surfaces or particles is given by the summation of the attractive and repulsive contributions.

VT = VA + VR

VT The total interaction energy VR The repulsive double layer interaction energy VA The attractive London-van der Waals energy


 * When two changed surfaces approach so that their electrical double-layers begin to overlap, a repulsive force is induced which tends to oppose further approach.
 * Suggests that double-layer repulsion will stabilize emulsion, when the electrolyte concentration phase is less than a certain value.
 * For small distances, the sum of the two energies is always – ve (i.e. net attractive) ⟹ cause aggregation
 * When the sum of two energies is + ve ⟹ repulsive force

Any question or suggestion??so that i can improve my presentation....thx..=)

 ﻿siew choo, i think it's better put some diagram. What do you think?
Actually I got try to put diagram...but i fail to upload....:( But i will put during presentation.... Thanks for suggest....reply by Siew Choo

HAII I!!! IT'S ME FASHA ..THIS IS MY SPACE.

..AND I WOULD LIKE TO SHARE WITH ALL OF YOU ABOUT TYPES OF ELECTROSTATIC FORCES

The following forces play an important role in the interaction of colloid particles:
 * **[|Excluded volume repulsion]**** : ** ** This refers to the impossibility of any overlap between hard particles. Higher repulsive force will form electrically change double layer. **


 * **Electrostatic interaction : ****Colloidal particles often carry an electrical charge and therefore attract or repel each other. The charge of both the continuous and the dispersed phase, as well as the mobility of the phases are factors affecting this interaction.**


 * **[|van der Waals forces]**** : ** ** This is due to interaction between two dipoles that are either permanent or induced. Even if the particles do not have a permanent dipole, fluctuations of the electron density gives rise to a temporary dipole in a particle. This temporary dipole induces a dipole in particles nearby. The temporary dipole and the induced dipoles are then attracted to each other. This is known as van der Waals force, and is always present (unless the refractive indexes of the dispersed and continuous phases are matched), is short-range, and is attractive. **