1. Dissolving is about ATTRACTION!
Part I: “Like dissolves Like”
Dissolving is about ATTRACTION!

2. OUTCOME QUESTION(S): C11-4-03 DISSOVING PROCESS Vocabulary & Concepts
Describe and give examples of various types of solutions.
Include: suspension, emulsion, colloid, alloy, solute,
solvent, soluble, insoluble, miscible, immiscible
Describe the chemical structure of compounds in terms of electronegativity and polarity of bonds.
Include: polar and non-polar
Explain the solution process of simple ionic and covalent compounds, using visual, particulate representation and chemical equations
Include: hydration, heat of solution, dissolve, dissociate
Vocabulary & Concepts 
Dipoles Solvation

3. Electronegativity
Scale (0-4) that represents the attraction an atom has for the shared pair of electrons in a bond
Most electronegative element is fluorine (F) = 4.0
Least electronegative element is cesium (Cs) = 0.7
In a compound, the atom with the higher electronegativity pulls the SHARED electrons closer

4. The interaction of the electrons between atoms determines the three types of possible bonds

5. Ionic bonds are easy to identify – look for metal?
Give/take of electron(s) to one atom in the bond
Caused by very large difference in EN values
Results in positive and negative IONS
Ionic bonds are easy to identify – look for metal? - +
EN = 0.9
EN = 3.0

6. Most covalent bonds are polar
2. POLAR Covalent Bond
Unequal sharing of electrons towards one atom
bigger the difference in EN, more polar the bond
Creates permanent +/- regions: DIPOLES
Most covalent bonds are polar
HCl δ+ δ-
Electrons pulled towards one side create a negative “end” and positive “end” + +
EN = 2.1
EN = 3.0

7. Diatomics and compounds of just C and H are common non-polar examples
3. NON-POLAR Covalent Bond
Equal sharing of electrons between atoms
very small or NO difference in EN
NO permanent dipoles
Diatomics and compounds of just C and H are common non-polar examples C H
propane C H Cl
chlorine gas
EN = 2.5
EN = 2.1
methane
EN = 3.0
EN = 3.0

8. Note: Some molecules can contain polar bonds, but because of the shape are considered to be non-polar molecules.
The geometry of some molecules cause all the polar “pulling” to cancel out resulting in no dipoles overall

9. **The general dissolving rule is like dissolves like**
Solvation: the process of dissolving…
Particles of solute will dissolve IF there is more attraction to the solvent particles than to itself.

10. Dissolving is usually endothermic overall
There are 3 steps to the dissolving process:
1. Solute particles must break apart.
Requires energy (called Lattice energy)
2. Solvent particles spread apart to make room.
Requires energy
3. Solute and solvent particles attract together.
Releases energy
Dissolving is usually endothermic overall
Heat of solution:
The sum of the energy changes for dissolving.

11. Water is a POLAR molecule
Hydration: dissolving with water as the solvent
If the solute is attracted to water it will dissolve
H2O δ- δ+ + +
EN = 3.5
EN = 2.1 + δ+
EN = 2.1

12. - - √ Case 1: Polar solvent (water) with Ionic solute + + DISSOLVEδ- δ+
DISSOLVE H O δ- δ+ H O δ- δ+ √ H O δ- δ+ - Cl Cl - Na + + Na
3 steps to dissolving:
1. Solute particles break apart.
2. Solvent particles spread apart.
3. Solute and solvent particles attract.
Dipoles attract Ions…
Attractive Force

13. Dipoles attract Dipoles…
Case 2: Polar solvent (water) with Polar solute H O δ- δ+
DISSOLVE H O δ- δ+ H O δ- δ+ √ H O δ- δ+ H O C δ- δ+ H O C δ- δ+
Dipoles attract Dipoles…
Attractive Force

14. X Case 3: Polar solvent with Non-polar solute DISSOLVEδ- δ+
DISSOLVE H O δ- δ+ H O δ- δ+ X H O δ- δ+ C H C H C H
Attractive Force
Nothing to attract…

15. No attraction or repulsion – free to mix
Case 4: Non-polar solvent with Non-polar solute
DISSOLVE √ H C H C H C C H C H C H
No attraction or repulsion – free to mix
Attractive Force

16. The more soluble a solute, the more attracted
**The general dissolving rule is like dissolves like**
Solutes are attracted to charged solvents to various degrees:
Remember that solubility is a relative term
The more soluble a solute, the more attracted
to the solvent it must be
Solute
Solvent
Polar
Non-polar
Ionic √ X

17. Allows tiny spheres of grease to "dissolve" in water
SOAP
Has a polar end and a non-polar tail.
Non-polar tail attracts oil
Polar head attracts water H O H O H O
Allows tiny spheres of grease to "dissolve" in water H O

18. CAN YOU / HAVE YOU? C11-4-03 DISSOVING PROCESS Vocabulary & Concepts
Describe and give examples of various types of solutions.
Include: suspension, emulsion, colloid, alloy, solute,
solvent, soluble, insoluble, miscible, immiscible
Describe the chemical structure of compounds in terms of electronegativity and polarity of bonds.
Include: polar and non-polar
Explain the solution process of simple ionic and covalent compounds, using visual, particulate representation and chemical equations
Include: hydration, heat of solution, dissolve, dissociate
Vocabulary & Concepts 
Dipoles Solvation