Separation Techniques 24/1/13

Pre-lab Questions on Distillation:

• What is the purpose of the boiling stones/chips?       

A boiling chip or boiling stone is a tiny, uneven shaped piece of substance added to liquids to make them boil more calmly. Boiling chips are frequently employed in distillation and heating. When a liquid becomes superheated, a particle of dust or a stirring rod can cause flash boiling. This very rapid boiling can be extremely violent and cause reagents to splatter, possibly causing severe burns, ruining an experiment, and damaging equipment. Boiling chips work by providing nucleation sites so the liquid boils smoothly without becoming superheated or bumping

• What is smooth boiling?

( refer to answer above ^)

1. What is the purpose of the thermometer and condenser?

condenser: to convert the gas form of a substance into a liquid. If the temperature and boiling points are kept constant, then the substance with the lower boiling point will be able to be evaporated and condensed, thus separated. The condenser ultimately just cools the gas form of the substance so it may return to the liquid state.

Thermometer: The thermometer on top measures the temperature of the vapor right before it condenses (boiling point).

1. Why does the water comes in from the top and out from the botton? (main purpose and purpose of position)

If water enters from the bottom of the condenser, it will always be completely filled with cold water which ensures efficient cooling. During distillation, vapors are formed in the heated distillation flask. The condenser cools these vapors condensing them back to liquid droplets that flow down the condenser into the receiver flask. A completely filled condenser provides maximum cooling therefore allowing for maximum recovery of the purified liquid during distillation.

Is it due to the concept of hot air rises and cold air sinks? ( Not Sure)

Theory Lesson:

Separation Techniques: mainly on Chromatography & Simple and Fractional Distillation

refer to slides on 'Separation Techniques Introduction'

references: - --http://www.chem.ualberta.ca/~orglabs/Techniques%20Extra%20Info/Distillation.html#same  - wikipedia

Elements' symbol learnt for test:

Helium

Lithium

Beryllium

Carbon

Nitrogen

Neon

Sodium

Magnesium

Tungsten

Aluminium

Silicon

Sulphur

Argon

Potassium

Calcium

Chromium

Cobalt

Silver

Gold 

Mercury

Extra: all of first 20 elements in periodic table