Heating & Cooling Curves / Separation Techniques

Heating & Cooling Curves

These are the basic terms for the changes of state of elements.

  

• This graph shows a heating curve of a pure substance.When the temperature increases, particles of  the substance move faster and kinetic energy increases as well.
• At point A, the substance is a solid.
• B--C is the melting point
• C indicates that the substance has finished melting and is now liquid.
• A slope of zero shows that the temperature stays the same because heat is used to overcome forces of attraction that holds the particles together.
• The heat absorbed is called a latent heat of fusion. 
• It occurs as a substanse changes its states.
• D--E is the boiling point
• E is when the substances has turned completely into gas.



 

• This graph shows a cooling curve of a pure substance.
• The substance starts out as a gas at point P and as the temperature decreases, the particles will come closer and lose energy.
• The heat energy released from Q to R is called latetn heat of vapourization.
• R is when the substance completes its change into a liquid state.
•  S--T is its freezing point
• The substance turns into solid at point T and then stays at room temperature

Separation Techniques

Components in a mechanical mixture retain their identities. Those mixtures that have different components can often be separated by devising a process that discriminates between components with different properties. The more similar the properties are, the more difficult to separate them.

Different properties that the components might have are:

• high density / low density
• volatile / non-volatile
• soluble / insoluble
• reactive / inert
• magnetic / non-magnetic
• polar  /non-polar

Some of the Basic Separation Techeniques

   

 1.Filteration

• separates solids that are not dissolved in liquids
• passing a mixture through a filter paper 
• residue left in filter = solid
• substance filtrate through = liquid

     

2.   Evapolation

• liquids & solids
• boiling away the liquid to retrieve a solid

Hand Separation

• Solid & solid
• separating mixture by using a  magnet or sieve

  

 3.  Crystallization

• Separates solid in liquids (precipitation) 
• solid is dissolved in liquid to form a saturated solution
• then, th substance is slowly evaporated and the solid will come out as crystals
•  the crystals can then be filtered out      

 4. Solvent Extraction

• Use a liquid to dissolve one solid but not both
• The desireable solid will be left behind or dissolved
• Since the sample separates, it is then possible to separate the components

   5. Gravity Seperation

• separates solid based on a difference in density
• a centrifuge whirls the test tube around at high speeds forcing the denser materials to the bottom

6. Distillation (based on boiling point)

• Heating mixtures can cause low-boiling components to volatilize
• then, collect and condense the evaporated material

    7.  Chromatography

• flowing of the mixture over a material that retains some components more than others, so different components flaw over the material at different speeds.