Solutions are homogeneous mixtures composed of a solute dissolved in a solvent. The solute is the substance being dissolved and is always present in smaller amounts, while the solvent does the dissolving and is present in larger amounts. Examples of solutions include cola, gasoline, and cleaners. Solutions can be solid, liquid, or gas depending on the state of matter of the solvent. For a solid solute to dissolve in a liquid to form a solution, it must be soluble, while if two liquids dissolve in each other they are miscible. The formation of solutions involves solvation and dissociation processes. Whether a substance dissolves depends on if it is polar or nonpolar, following the "like dissolves like"

1. Solutions
Unit 9: Solutions

2. What are solutions?
• Solutions are homogeneous mixtures
–Look the same throughout
• Combined physically (not chemically)
• You CAN separate by physical means
using filtration, distillation, or
evaporation.
• Examples: Cola, Gasoline, Cleaners

3. What are solutions?
• Solutions have two parts:
–Solute
–Solvent
Solute
Solvent

4. What are solutes and solvents?
• The solute is the substance being
dissolved and it is always present in
smaller amounts
• The solvent is doing the dissolving
and is always present in larger
amounts
–AKA the dissolving agent

5. What are solutes and solvents?
• Example: Kool-Aid
• What is the solute?
–Kool-Aid Powder because it is being
dissolved and there is less of it
• What is the solvent?
–Water because it is doing the dissolving and
there is more of it
Solute + Solvent = Solution

6. What are the types of solutions?
• Solutions can be solid, liquid, or gas
based on the solvent’s state of matter
because there is more of it!
–Example: Air is a solution with the solvent
being nitrogen and solute being oxygen
because ~75% of air is nitrogen and ~24% of
air being oxygen
• Not all substances can form solutions!
• If a solid solute can dissolve in a liquid, it
is called soluble
–Kool-aid is soluble in water

7. What are the types of solutions?
• If two liquids dissolve in each other they are
miscible
– Food coloring is miscible in water
• If a solid solute cannot dissolve in a liquid, it
is insoluble
– Sand is insoluble in water
• If two liquids cannot dissolve in each other,
they are immiscible
– Oil and water are immiscible
– Meniscus will be visible if two liquids are
immiscible!

9. What are the steps of solution formation?
1. Solvation: the solvent particles
completely surround solute particles
– Called hydration if solvent is water
2. Dissociation: ions are pulled apart by
solvent and seem to “disappear”

11. How do we know if something is soluble?
• The substances involved in making a
solution are either polar or nonpolar
• If a substance is polar, it has regions
of opposite charge
–Ionic compounds are usually polar

12. How do we know if something is soluble?
• If a substance is nonpolar, it does not
have regions of opposite charge
–Covalent compounds are usually
nonpolar
• EXCEPTION: Water is covalent and
polar
• Nicknamed “universal solvent”
because of its unique solution
properties

13. Practice
• Are the following polar or nonpolar?
• NaCl
–Polar – Ionic
• KBr
–Polar – Ionic
• CH4
–Nonpolar – Covalent

14. How do we know if something is soluble?
• Rule: “Like Dissolves Like”
• Polar solvents dissolve polar solutes
• Nonpolar solvents dissolve nonpolar
solutes
• Polar solvents WILL NOT dissolve
nonpolar solutes