Chapter 13c: Solubility of Solutes

Key Concepts

Solute: The substance in the lesser amount in a solution, which is dissolved, e.g., salt.
Solubility: The ability of a substance to dissolve.
- Soluble means the substance will dissolve.
- Insoluble means the substance will not dissolve.

"Like dissolves like"
- Polar substances tend to dissolve other polar substances.
- Non-polar substances tend to dissolve other non-polar substances.
- Polar and non-polar substances do not mix well together.

Oil and Water: A classic example where oil (non-polar) and water (polar) do not mix, forming separate layers.
Non-polar Compounds:
- Made of carbons, hydrogens, and sometimes oxygens.
- Molecules do not have a strong attraction to one another, unlike polar molecules.
- Example: Styrofoam beads as a model for non-polar interactions – no strong attraction occurs.
Polar Compounds:
- Act like magnets with positive and negative ends.
- Molecules attract each other due to these charges.
- Examples: Water, ionic compounds like sodium chloride, alcohols, and some sugars.
- Typically have an oxygen atom involved with carbon and hydrogen, contributing to polar characteristics.

Non-Polar Molecules:
- Examples: Oil, kerosene, gasoline, propane, butane, and organic solvents.
- Also include diatomic molecules like bromine, chlorine, iodine with zero electronegativity difference.
Polar Molecules:
- Water is the most common polar compound, capable of dissolving many ionic and some covalent compounds.

Observation: When added to a mixture of oil and water, food coloring tends to mix with the polar (water) layer rather than the non-polar (oil) layer.
Question: Is food coloring polar or non-polar? It appears to be more soluble in water (polar), thus indicating it is polar.

Understanding solubility and the "like dissolves like" rule helps to predict how substances interact in solutions.
Practical applications include understanding everyday phenomena like oil and water separation and the solubility of household substances.