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WRITE ABOUT THE FOLLOWING 
1. MIXTURE AND COMPOUND 
2. COLLOIDS AND SUSPENSION 
3. DISTILLATION 
4. CHROMATOGRAPHY 

Dear Student,

Suspension – Heterogeneous mixture of solids and liquids Solid particles suspend throughout the medium Properties
 Heterogeneous mixture
 Particles visible by the naked eye
 Light path visible
 Particles settle down
 Solute particles can be separated by filtration
Example – sand in water

Properties of a colloid
 Heterogeneous mixture
 Particle size is small, not visible to the naked eye
 Light path can be visible
 Particles do not settle down
 Substances cannot be separated by filtration
Example – milk

Distillation is a process which is used to separate a mixture of two miscible liquids that boil without decomposition and at different temperatures. When the difference in the boiling point of the two liquids is 25K or more, we use simple distillation. However when the differences in the boiling points of the components of a mixture is less than 25K, fractional distillation is employed. The boiling point of water is 100 degree Celsius (373 on Kelvin scale) while the boiling point of acetone is 56 degree Celsius (329K on K scale). The difference between the boiling points of the two compounds is 44K, which is much greater than 25K. Hence simple distillation can be used to easily separate the mixture of acetone and water.

Chromatography is the technique used for separation of the components of a mixture that are soluble in the same solvent. This technique was first used for separation of colours, so this name was given. There are two phases in chromatography - the stationary phase and the mobile phase. The components of the mixture are absorbed differently on the stationary phase, thus leading to their separation.

There are many different types of chromatography - paper chromatography, thin layer chromatography, gas chromatography etc. You will study about them in higher grades.

Mixture Compound
1. The proportion of two or more substances in indefinite ratio. 1.The proportion of two or more constituent particles are fixed by mass.
2.The constituent particles maintain their individual nature. 2. The constituent particles nature are not visible rather a new substance with different properties are found.
3.The constituents can be separated easily by physical methods. 3.Its constituent could be separated only by chemical methods.      
4. Ex: Salt and water solution. 4. Ex: Water, ( H2O).

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1 Molecules & Compounds

When atoms from different elements are joined together in groups, they form molecules. The atoms in molecules bind together chemically, which means that the atoms cannot be separated again by physical means, such as filtration. The molecule has different properties from the elements from which is was made. A water molecule is not three separate atoms, two hydrogen (H) and one oxygen (O), but it is actually a unique H2O molecule.

There are more carbon compounds than compounds of any other element. Organic compound is the name for the carbon compounds found in all living things.

Mixtures - A Bit of This and That

All matter can be classified into two categories: pure substances and mixtures. A pure substance consists of a single element or compound. Iron is formed only of iron (Fe) atoms; table salt is formed only by sodium chloride (NaCl) molecules. A mixture, however, is made up of different compounds and/or elements. When salt is added to water to make saltwater, it becomes a mixture. The salt and water molecules do not combine to form new molecules, but only "mix" together while still retaining their identities. Air is also a mixture, containing just the right amounts of nitrogen, oxygen, and other gases for life on Earth.

2.

Suspensions

The particles in suspensions are larger than those found in solutions. Components of a suspension can be evenly distributed by a mechanical means, like by shaking the contents, but the components will settle out.

 

Example: Oil and Water

More Examples of Suspensions

Colloids

Particles intermediate in size between those found in solutions and suspensions can be mixed such that they remain evenly distributed without settling out. These particles range in size from 10-8 to 10-6 m in size and are termed colloidal particles or colloids. The mixture they form is called a colloidal dispersion. A colloidal dispersion consists of colloids in a dispersing medium.

Example: Milk

3.

Distillation is a widely used method for separating mixtures based on differences in the conditions required to change the phase of components of the mixture. To separate a mixture of liquids, the liquid can be heated to force components, which have different boiling points, into the gas phase. The gas is then condensed back into liquid form and collected.

 

Repeating the process on the collected liquid to improve the purity of the product is called double distillation. Although the term is most commonly applied to liquids, the reverse process can be used to separate gases by liquefying components using changes in temperature and/or pressure.

A plant that performs distillation is called a distillery. The apparatus used to perform distillation is called a still.

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