1. Formation of Solutions
Chapter 8
Section 8.1
Formation of Solutions

2. Formation of Solutions
A solution is a homogeneous mixture of two or more substances, consisting of ions or molecules.
For a solution to form, one substance must dissolve in another.

3. Solute and Solvent Too simplify: What two things make up a solution?
A solute and a solvent.
What is a solute?
Something that gets dissolved in a solvent.
What is a solvent?
Something that dissolves a solute.

4. Types of Solutions Solutions may exist as gases, liquids, or solids.
The solute is the dissolved substance. In the case of a solution of a gas or solid in a liquid, it is the gas or solid. Otherwise, it is the component of lesser amount.
The solvent is the dissolving medium. Generally it is the component of greater amount.

5. Examples of Solutions Type Example Solute Solvent Windshield Washer
Gas in Gas
Air
Oxygen
Nitrogen
Gas in liquid
Soda
Carbon dioxide
(gas)
Water
(liquid)
Solid in Liquid
Seawater
Salt (solid)
Water (Liquid)
Liquid in Liquid
Windshield Washer
Alcohol
Solid in Solid
Brass
Zinc (solid)
Copper (solid)

6. Substances Dissolving in Water
Three Ways:
Dissociation
Dispersion
Ionization

7. Dissociation Ionic compounds
metal + nonmetal (Binary and Multivalent)
metal + polyatomic anion
polyatomic cation + anion
When ionic compounds dissolve in water the anions and cations are separated from each other; this is called dissociation
We know that ionic compounds dissociate when they dissolve in water because the solution conducts electricity

8. Dispersion of Molecular Compounds
Sugar dissolves in water by dispersion, or breaking into small pieces that spread throughout the water.
A substance dissolves in water by breaking up into smaller pieces. These pieces of the same substance spread throughout the water. This process is known as dispersion.

9. Ionization of Molecular Compounds
The process in which neutral molecules gain or lose electrons is known as ionization.
Unlike dissociation and dispersion, which are physical changes, dissolving by ionization is a chemical change. The solution that results contains new substances.

10. Properties of Liquid Solutions
Three physical properties of a solution that can differ from those of its solute and solvent are:
Conductivity
Freezing Point
Boiling Point .

11. Conductivity The current is carried by dissolved ions
The ability of an ion to carry current is a function of:
Ions charge (more charge, more current)
Ions mass or size (larger ions, conduct less)

12. Freezing Point
Freezing Point Depression
Lowering the freezing point of a solution as a result of the dissolved solute
The presence of solute particles affects how the solvent freezes.

13. Boiling Point
Boiling Point Elevation
Raising the boiling point of a substance by adding solute

14. Heat of Solution
During the formation of a solution, energy is either released or absorbed.
Like chemical reaction, the solution process can be described as exothermic or endothermic.
Dissolving sodium hydroxide in water is exothermic because it releases heat. Dissolving ammonium nitrate is endothermic because it absorbs heat.
In order for a solution to form, both the attractions among solute particles and the attractions among solvent particles must be broken.
In an exothermic reaction, the amount of energy required to break the attractions among the solute particles and among the solvent particles is less than the energy released as attractions form between solute and solvent particles.

15. Heat of Solution The formation of attractions releases energy.
In an exothermic reaction, the amount of energy required to break the attractions among the solute particles and among the solvent particles is less than the energy released as attractions form between solute and solvent particles.
The formation of attractions releases energy.
The difference between these energies is known as the heat of solution.

16. Factors Affecting Rates of Dissolving
Like rates of chemical reactions, rates of dissolving depend on the frequency and energy of collisions that occur between very small particles.
During a chemical reaction, collisions occur between particles of the reactants.
During the formation of a solution, collisions occur between particles of the solute and solvent.
Factors that affect the rate of dissolving include surface area, stirring, and temperature.

17. Factors Affecting Rates of Dissolving
Temperature
If we heat particles they will move faster
The solvent will carry the solute particles away faster
So… Hotter Faster

18. Factors Affecting Rates of Dissolving
Stirring or Shaking
Stirring or shaking a solution moves the solute particles around so that they are closer to water particles
the water particles can then attract them easily and carry them away!
So…. Dissolve Faster

19. Factors Affecting Rates of Dissolving
Surface Area
When broken into small particles
the water particles can then attract them easily and carry them away!
When solute is broken up, there is more surface area where dissolving can occur
So…smaller surface area faster dissolves