Heating & Cooling Curve and Speperating Techniques

Heating Curve (added notes to diagram)

A -> B: 

heat energy converts to kinetic energy
particles vibrate faster, temperature increase

B: still solid

B-> C: 

solid-> liquid
temperature remains constant because heat used to overcome force of attraction
melting point- heat absorbed is called heat of fusion
C: liquid
(all solids have melted)
C->D
temperature and KE increases

Cooling Curve
P: Gas
particles have high energy and move quickly
P -> Q
KE decreases (particles getting closer)
temperature decreases
Q
condensation (stronger bonds formed)
temperature remains constant
heat energy released is call latent heat of vaporization
R: Liquid
R-> S
molecules loose energy
particles move slower and closer to each other
temperature decreases
S: starts to freeze to solid
S->T -Liquid to Solid
particles arranged in an ordered manner
freezing point
T->U
temperate decreases
U: Substance has reached room temperature


Separating Techniques


Strategy: devise a process that discriminates between components/properties

Seperation
-components in a mixture retain their identities
- more similar the properties, more difficult to seperate

Basic Techniques
Hand Separation (solid and solid)
- mechanical mixture can be separated by using magnet or sieve
Evaporation (solid dissolved in liquid)
- boil away liquid; solid remains
Filtration (solid (not dissolved) and liquids)
- pass mixture through porous filter
-use filter paper-residue left in filter; filtrate goes through
Crystallization (Solid in liquid)
- precipitation
- solids are then separated by filtration or flotation
- use a saturated solution of desired solid
- evaporate and cool-solid comes out as pure crystals.
Gravity Separation (Solids based on density)
- a centrifuge whirls the test tube at high speeds forcing denser materials on bottom, (better for small volumes)
Solvent Extraction
Mechanical Mixture: use liquid to dissolve one solid, not other
Solution: solvent is insolvable with solvent already present
Distillation (liquid in liquid solution)
- heating a mixture can cause low boiling point component to vaporize(volatized)
- collect condensed volatized components
Chromatography
- flow the mixture that retains some components more then others so different components flow over the material at different speeds (a mobile phase sweeps a stationary phase)
Paper Chromatography
-stationary phase is liquid soaked into sheep or strip of paper
-components appear as a separate spots spread out on paper after drying or "developing"
Thin layer Chromatography
-stationary phase is a thin layer of absorbent (sheet of plastic or glass)
-some components bonded to the absorbent strongly; others weakly