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# FACTORS AFFECTING RATE OF DISSOLVING AND SOLUBILITY

FACTORS AFFECTING RATE OF DISSOLVING AND SOLUBILITY. SECTION 8.2. FACTORS AFFECTING RATE OF SOLUBILITY. TEMPERATURE High temp  more kinetic energy Particles collide with each other This increases their rate of dissolving. FACTORS AFFECTING RATE OF SOLUBILITY. PARTICLE/ MOLECULE SIZE

## FACTORS AFFECTING RATE OF DISSOLVING AND SOLUBILITY

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1. FACTORS AFFECTING RATE OF SOLUBILITY • TEMPERATURE • High temp  more kinetic energy • Particles collide with each other • This increases their rate of dissolving

2. FACTORS AFFECTING RATE OF SOLUBILITY • PARTICLE/ MOLECULE SIZE • smaller particle size = higher the rate of solubility • Because smaller particles fit more readily between the water molecules • Ex: Small molecule vs large molecule

3. FACTORS AFFECTING RATE OF SOLUBILITY • AGITATION • Ex: Dissolve sugar in coffee • Stirring the sugar agitates the molecules • Agitation = higher rate of solubility

4. FACTORS AFFECTING RATE OF SOLUBILITY • SURFACE AREA • The more spread out the particles are, the higher the rate of solubility • Ex: A powder will dissolve more readily than a cube of the solute

5. SOLUBILITY AT A MOLECULAR LEVEL • Forces of attraction between solute and solvent particles affect rate of solubility • Which forces? • Between solute particles • Between solvent particles • Between solute and solvent particle

6. 3 STEP PROCESS • 1) Forces between particles in solid (SOLUTE) must be broken • Requires energy • 2) Intermolecular forces between particles in the liquid (SOLVENT) must be broken • Requires energy • 3) Attraction between the particles of the solid (SOLUTE) and the particles of the liquid (SOLVENT) • Gives off energy

7. POLAR vs NON-POLAR

8. POLAR vs NON POLAR REVIEW • POLAR • Forms dipoles (δ+ and δ-) • Dissolve in other polar substances • Ex: Sucrose in water • NON POLAR • Covalently bonded molecule that doesn’t form dipole • Dissolves in other non-polar substances • Ex: Iodine and kerosene

9. RECALL: 2 TYPES OF INTERMOLECULAR FORCES • 1) Dipole- Dipole • Between opposite charges on 2 different polar molecules • Special kind of dipole-dipole force seen in water: HYDROGEN BONDING

10. DIPOLE DIPOLE cont..d • As a result, every water molecule can form 4 Hydrogen bonds to other water molecules

11. RECALL: 2 TYPES OF INTERMOLECULAR FORCES • 2) Ion- Dipole • Attractive forces between an ion and a polar molecule • If ion-dipole force CAN replace the ionic bonds [cations (+) and anions (-)], the compound WILL dissolve • Ex: NaCl and Water

12. Ex: NaCl and Water

13. ION- DIPOLE ATTRACTIONS cont…d • GENERALLY, ionic compounds dissolve in polar substances (there are some exceptions: eg: AgCl) • If the solution is “aq” (in water), each ion is HYDRATED (surrounded by H2O molecules) • Hydrated ions can conduct electricity; such solutions are called ELECTROLYTES

14. MAIN IDEA… • "Like dissolves like" • Polar dissolves polar • Non-polar dissolves non-polar • Polar DOES NOT dissolve non-polar • Non-polar DOES NOT dissolve polar

15. SOLUBILITY AND COVALENT COMPOUNDS • Many covalent compounds do not have (-) and (+) charges • Thus, they are NOT soluble in water • A few exceptions: • Methanol • Ethanol • Sucrose • Dissolve because they contain POLAR bonds • However, they do NOT conduct electricity; called NON-ELECTROLYTES

16. HOMEWORK • Page 301 # 1, 2, 4 • MUST be done or you will be LOST tomorrow! 

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