physical seperation process and some pics

Filtration, distillation, paper chromatography, sublimation and crystallization

Filtration

Filtration is a physical operation which is used for the separation of solids from fluids (liquids or gases) by interposing a medium through which only the fluid can pass.

An example which could be separated by hand might be a dry mixture of salt and sand. Manually picking out the sand does not change the chemical identity of the salt or the sand.

Filtration is the most common technique to remove the solid material

What we need:

-          Filter paper

-          Beaker / Test Tube

-          Funnel

Example we want to remove the water from sand mixture (water-sand):

1.      Put the water-sand mixture, in a beaker/test tube according to the amount.

2.      Prepare the filter paper, fold it like the picture beside, then put it inside the funnel

3.      Put the funnel on the 2^nd beaker/test tube, then pour the mixture

The water is called the filtrate.

The sand is called the residue.

Distillation

Distillation is the process of heating a liquid until it boils, capturing and cooling the resultant hot vapors, and collecting the condensed vapors. Distillation is a method of separating mixtures based on differences in their volatilities in a boiling liquid mixture.

Materials we need:

- A flask equipped with a thermometer and with an outlet tube from which the vapor is emitted;

- A condenser that consists of two tubes of different diameters placed one within the other and so arranged that the smaller (in which the vapor is condensed) is held in a stream of coolant in the larger ; and

- A vessel in which condensed vapour collected

Steps:

   The mixture of substances is placed in the flask and heated. Ideally, the substance with the lowest boiling point vaporizes first (see vaporization ), the temperature remaining constant until that substance has completely distilled. The vapor is led into the condenser where, on being cooled, it reverts to the liquid (condenses) and runs off into a receiving vessel.

Sublimation

Sublimation is the separation of mixture based on their properties, whether they can sublimate or not. Sublimation is a technique used by chemists to purify compounds. Typically a solid is placed in a sublimation apparatus and heated under vacuum

Example:

The purification of dirty naphthalene.

Steps:

The solid naphthalene is placed in an enclosed bottle and then heated. Consequently, the naphthalene will sublime into vapours. The vapours will be stucked in the inner side of the bottle’s lid and the impurities will be retained at the bottom of the bottle. By condensing, we can obtain clean naphthalene.

                                                                                                             

Crystallization

Crystallization is the separation of mixtures based on the difference in the vapourizing of substances in the mixtures. The substances that can’t be evaporated will be retained in the bottom of the container as crystals.

Example:

Getting salt from seawater.

Steps:

Seawater is put inside tubs. It will directly make a contact directly with sunlight, so water will evaporate and salt will be retained at the bottom of the tubs.

sublimator

Chromatography

Chromatography is used to separate chemical substances that have different rates of spreading in a specific solvent. Ex: the separation of ink colours

Materials we need:

·         Paper coffee filters
• One black permanent pen
• Black water soluble pens
• Container full of water
• Several sheets of paper
• Small glasses or plastic containers
• Isopropyl rubbing alcohol*
• Pencils
• Tape
• Scissors
• Stapler

Steps:

Part I - Separating Black Ink
1. Cut several coffee filters into long strips, one strip per pen.
2. Fold the end of each strip over then staple it to form a loop.
3. Place a dot of ink near the bottom of each strip. Use a pencil to identify which strip belongs to which pen.

4. Poke a pencil through one of the loops you just made. Use the pencil to suspend the strip in a small glass or container.
5. Carefully add water to the glass until it reaches the bottom of the paper strip just below the ink dot. Be sure the ink stays above the water and the paper stays in the water.
6. Allow the water to soak up the strip and watch what happens to the ink drop.
7. If the ink you are testing does not spread out, re-test it using rubbing alcohol.
8. Repeat this process for each strip and compare your results.
9. Let the strips dry and tape them on a sheet of paper as a record of the different pen types.

WHAT’S HAPPENING

Because molecules in ink and other mixtures have different characteristics (such as size and solubility), they travel at different speeds when pulled along a piece of paper by a solvent (in this case, water). For example, black ink contains several colours. When the water flows through a word written in black, the molecules of each one of the colours behave differently, resulting in a sort of “rainbow” effect.
     Many common inks are water soluble and spread apart into the component dyes using water as a solvent. If the ink you are testing does not spread out using water, it may be “permanent” ink. In such cases, you will have to use a different solvent such as rubbing alcohol.