ASSIGNMENT PHYSICAL CHEMISTRY:
FAQIHAH ILYANA BINTI MOHD SHALAHUDIN
2016537995
AS2532C
1. List the types of colloid properties and explain each of the properties.
= The types of colloid properties consist of optical properties and also electrical properties.
Optical properties involved of Tyndall effect and also Brownian movement while electrical
properties involved of electrophoresis and electro-osmosis. As for Tyndall effect in optical
properties, it was first observed by John Tyndall who was a British Physicist in 1869 where
Tyndall effect or known as Tyndall scattering is the effect of light scattering in colloidal
dispersion, while showing no light in a true solution. This effect is used to determine whether a
mixture is a true solution or a colloidal solution. It is observed when a beam of light passes
through a colloidal solution, the light is scattered by the particles present in the colloidal
solution. The amount of scattering depends on the frequency of the light and density of the
particles. For example, by shining a flashlight beam into a glass of milk where the light will be
reflected in all directions when it passes through the milk because milk is a colloidal solution but
not in water. Next, Brownian movement as optical colloid properties is known as the zigzag
movement of colloidal particles. The colloidal particles are too small to be visible and it can only
be seen under a high-power microscope. Brownian movement is where the colloidal particles and
molecules of dispersion medium are in a constant motion undergoing continuous collision and
passes kinetic energy to colloidal particles by striking it from all sides. While as for electrical
properties that involved electrophoresis which is the movement of the colloidal particles under
the influence of an applied electric potential. It occurs when the colloidal particles migrate to
oppositely charged electrode to get neutralized due to an electric field that has applied across the
colloidal solution. Then, as for electro-osmosis properties where when the electrophoresis of
dispersed particle in a colloid solution is prevented by some suitable means and it is observed
that dispersion medium itself begins to move in an electric field.
2. Discuss the differences between lyophilic and lyophobic colloid.
= Lyophilic colloids are known as liquid loving colloids while lyophobic colloids are known as
liquid hating colloids. It can be differentiate by the mode of preparation where lyophilic can be
prepared directly by mixing colloid with liquid and no additional stabilizers are required while
for lyophobic in which it cannot be prepared directly by mixing colloid with liquid but using
special methods and additional stabilizers are required. Next, as for the stability properties where
the lyophilic colloid is more stable compared to lyophobic as strong forces of interaction exist
between the colloidal particles and liquid in lyophilic but only weak forces of interaction in
lyophobic. These colloids also have differences in their viscosity where lyophilic colloids have
higher viscosity than that of the medium but as for lyophobic colloids, it has almost the same
viscosity as the medium. Furthermore, the nature of the colloid in which lyophilic colloids is a
reversible because the residue left on evaporating the liquid will passes into colloid state on
addition of liquid while lyophobic is an irreversible because the residue left cannot be converted
into the solution on mere addition of liquid. Other than that, the visibility for both lyophilic and
lyophobic colloid where lyophilic particles cannot be easily detected under ultra- microscope but
the lyophobic particles are easily detected. Lastly, as for the charge of these particles in which
lyophilic particles depends upon pH of the medium that may be positive, negative or neutral and
lyophobic particles only carry either positive or negative charge.
REFERENCES:
1. http://www.majordifferences.com/2013/11/difference-between-lyphobic-
and.html#.WTWiH_nyvIU
2. http://www.chemistrylearning.com/difference-between-lyophobic-and-lyophilic/
3. https://chem.libretexts.org/Core/Physical_and_Theoretical_Chemistry/Physical_Propertie
s_of_Matter/Solutions_and_Mixtures/Colloid/Tyndall_Effect
4. http://www.chemistrylearning.com/properties-of-colloids/
5. https://www.thoughtco.com/definition-of-tyndall-effect-605756
6. http://www.chemavishkar.com/2012/09/what-are-colloidstheir-properties-and.html
