English: Major destabilisation mechanisms for liquid dispersions (Photo credit: Wikipedia)
→ Solvent added (clear) to compound (orange) → Solvent heated to give saturated compound solution (orange) → Second solvent (blue) added to compound solution (orange) to give mixed solvent system (green) → Mixed solvent system (green) allowed to cool over time to give crystals (orange) and a saturated mixed solvent system (green-blue). (Photo credit: Wikipedia)
→ Solvent added (clear) to compound (orange) → Solvent heated to give saturated compound solution (orange) → Saturated compound solution (orange) allowed to cool over time to give crystals (orange) and a saturated solution (pale-orange). (Photo credit: Wikipedia)
English: The connectivity of particles within the crystaline domains of a 2D solid-in-liquid colloid. White indicates a particles 6 neighbour connections as found in crystaline domains. Other darker colours indicate more or less neighbours in amorphous domains. (Photo credit: Wikipedia)
Solution of Salt in Water (regular table salt, regular tap water) Русский: Растворение соли в воде (Photo credit: Wikipedia)
MIXTURE
What is a Mixture?
Two or more substances which have been combined such that each
substance retains its own chemical identity.
A mixture is the blending of two or more dissimilar substances that do
not chemically combine to form compounds and that can typically be
separated by non-chemical means.
Examples: Flour and sugar may be combined to form a mixture.
TYPES OF MIXTURES
Mixtures can be classified into three types: suspension mixture, colloidal
mixture or solution, according to how they combine and can be
separated.
1 . Suspension mixture
A suspension mixture is usually created by stirring together two or more
ingredients, where the particles are typically large enough to be seen by
the unaided eye or a magnifying glass. The ingredients of a suspension
mixture are heterogeneous, meaning that they are not evening
distributed throughout. Most mixtures are suspension mixtures.
Solid-solid mix
Many suspension mixtures consist of solids mixed with solids. Cake mix
is an example of visible solid particles mixed together by a means of
stirring. Dirt or soil is another example of a solid-solid suspension
mixture.
These mixtures can be separated by sifting. Sometimes shaking will cause
the heavier particles to settle to the bottom.
Solid-fluid mix
If solid particles are mixed in a liquid or gas to form a suspension mixture,
the ingredients will soon separate, with the heavier solid particles settling
at the bottom. For example, if you mixed sand and water, the sand would
soon sink to the bottom.
If the solid particles are lighter than the liquid–as in the case of sawdust
mixed in water–they will separate and float to the top.
A major part of air pollution consists of smoke and dust particles mixed
within the atmosphere. This is a suspension mixture. After a while, the
these solid particles will settle to the ground.
Besides settling, filtration can also be used to separate the ingredients.
Fluid-fluid mix
If visible globules of a liquid are mixed in a liquid or gas solvent, the
ingredients will soon separate. If the globules are heavier, they will settle
at the bottom. If the globules are lighter, they will float to the top.
2 . Colloidal mixture
A colloidal mixture is a homogeneous combination of solid or liquid particles
mixed within a liquid or gas solvent.
Properties of a colloid
• A colloid is a heterogeneous mixture.
• The size of particles of a colloid is too small to be individually seen by
naked eyes.
• Colloids are big enough to scatter a beam of light passing through it and
make its path visible.
• They do not settle down when left undisturbed, that is, a colloid is quite
stable.
• They cannot be separated from the mixture by the process of filtration.
But, a special technique of separation known as centrifugation can be used
to separate the colloidal particles.
Common examples of colloids
Size of particles
The sizes of solute particles in a colloidal mixture are much smaller than
the particles in a suspension, but they are not as small as those in a
solution. The particles in a colloidal mixture are typically as small as a
clump of molecules that may not even be visible with a common
microscope.
What makes a colloidal mixture unusual is that the solute particles do not
break down any further to be single molecules–thus forming a solution.
Instead, “something” coats the particles and prevents them from
completely dissolving in the solvent.
Blending
The blending of materials in a a colloidal mixture is usually more
aggressive than the simple stirring done in a suspension. Often the
material is violently mixed or shaken. A good example is the paintmixer
machine that actively shakes the can to thoroughly mix the paint
materials to minimize settling.
Some examples of colloidal mixtures are mayonnaise, Jell-O, fog, butter
and whipped cream.
Solution
A solution is a homogeneous mixture where one substance is dissolved
in another substance. The solute dissolves in the solvent. The solvent is
a liquid or gas, and the solute can be a solid, liquid or gas.
A solution has a solvent and a solute as its components. The component
of the solution that dissolves the other component in it (usually the
component present in larger amount) is called the solvent. The
component of the solution that is dissolved in the solvent (usually present
in lesser quantity) is called the solute.
Examples:
(i) A solution of sugar in water is a solid in liquid solution. In this solution,
sugar is the solute and water is the solvent.
(ii) A solution of iodine in alcohol known as ‘tincture of iodine’, has iodine
(solid) as the solute and alcohol (liquid) as the solvent.
(iii) Aerated drinks like soda water etc., are gas in liquid solutions.
These contain carbon dioxide (gas) as solute and water (liquid) as
solvent.
(iv) Air is a mixture of gas in gas. Air is a homogeneous mixture of
a number of gases. Its two main constituents are: oxygen (21%) and
nitrogen (78%). The other gases are present in very small quantities.
Properties of a solution
• A solution is a homogeneous mixture.
• The particles of a solution are smaller than 1 nm (10-9 metre) in
diameter. So, they cannot be seen by naked eyes.
• Because of very small particle size, they do not scatter a beam of light
passing through the solution. So, the path of light is not visible in a
solution.
• The solute particles cannot be separated from the mixture by the
process of filtration. The solute particles do not settle down when left
undisturbed, that is, a solution is stable.
CONCENTRATION OF A SOLUTION
In a solution the relative proportion of the solute and solvent can be
varied. Depending upon the amount of solute present in a solution, it can
be called a dilute, concentrated or a saturated solution.
At any particular temperature, a solution that has dissolved as much solute
as it is capable of dissolving, is said to be a saturated solution.
The amount of the solute present in the saturated solution at this
temperature is called its solubility.
If the amount of solute contained in a solution is less than the saturation
level, it is called an unsaturated solution.
The concentration of a solution is the amount of solute present in a given
amount (mass or volume) of solution, or the amount of solute dissolved
in a given mass or volume of solvent.
Amount of Solute
Concentration of solution =
Amount of Solution
Or
Amount of Solute
Amount of Solvent
There are various ways of expressing the concentration
of a solution.
(i) Mass by mass percentage of a solution
Mass of Solute
= × 100
Mass of Solution
(ii) Mass by volume percentage of a solution
Mass of Solute
= × 100
Volume of Solution
Example 2.1 A solution contains 40 g of common salt in 320 g of water.
Calculate the concentration in terms of mass by mass percentage of the
solution. Solution:
Mass of solute (salt) = 40 g
Mass of solvent (water) = 320 g
We know,
Mass of solution = Mass of solute + Mass of solvent
= 40 g + 320 g
= 360 g
Mass percentage of Solution
Mass of Solute
= × 100
Mass of Solution
=40/360 × 100 = 11.1%
Dissolving
Dissolving means that after the solute is put in the solvent, it breaks to
an atomic, ionic or molecular level and can no longer be seen as a
separate entity. For example, mixing the solid material salt into the liquid
water results in the salt dissolving into water and creating the salt water
solution. The salt breaks into Sodium (Na
+
) and Chlorine (Cl
-) ions within
the water solvent.
Polar or non-polar
Typically, all the molecules in a solution are either polar or non-polar. For
example, Nitrogen (N2), Oxygen (O2) and Carbon Dioxide (CO2) are all
non-polar molecules. They mix well together to form the solution we call
air.
Under normal conditions combinations of polar and non-polar molecules
do not mix to form a solution. There are exceptions, such as the nonpolar Carbon Dioxide dissolving in the polar solvent water (H2O) under
high pressure.
Separation
The solute and solvent in a solution cannot be separated unless one of
the ingredients changes state of matter. For example, by heating the
solution, one material may evaporate. This is also called distillation.
Types of Pure Substances
On the basis of their chemical composition, substances can be classified
either as elements or compounds.
ELEMENTS- Element is a basic form of matter that cannot be broken down
into simpler substances by chemical reactions.
Elements can be normally divided into metals, non-metals and metalloids.
Metals usually show some or all of the following properties:
• They have a lustre (shine).
• They have silvery-grey or golden-yellow colour.
• They conduct heat and electricity.
• They are ductile (can be drawn into wires).
• They are malleable (can be hammered into thin sheets).
• They are sonorous (make a ringing sound when hit).
Examples of metals are gold, silver, copper, iron, sodium, potassium etc.
Mercury is the only metal that is liquid at room temperature. Nonmetals
usually show some or all of the following properties:
• They display a variety of colours.
• They are poor conductors of heat and electricity.
• They are not lustrous, sonorous or malleable. Examples of non metals are
hydrogen, oxygen, iodine, carbon (coal, coke), bromine, chlorine etc.
Some elements have intermediate properties between those of metals
and non-metals, they are called metalloids; examples are boron, silicon,
germanium etc.
COMPOUNDS- A compound is a substance composed of two
or more elements, chemically combined with one another in
a fixed proportion.
Mixtures and Compounds
Note Blast 