Chemistry: IMFs, Phase Changes, & Dissolution Key Concepts

What are intermolecular forces (IMFs)?

Attractions between molecules that affect boiling point, melting point, solubility, and viscosity.

What are London Dispersion Forces (LDF)?

Weakest IMFs present in all molecules, caused by temporary, induced dipoles from uneven electron distribution.

How do London Dispersion Forces (LDF) strength change?

Strength increases with more electrons and larger surface area.

Which type of molecules primarily exhibit dipole-dipole forces?

Polar molecules.

What is hydrogen bonding?

A strong IMF occurring when hydrogen is bonded to highly electronegative elements like O, N, or F.

How do stronger intermolecular forces affect boiling point?

Stronger IMFs lead to a higher boiling point.

What is the relationship between melting point and intermolecular forces?

Stronger IMFs result in a higher melting point.

What does 'like dissolves like' mean in terms of solubility?

Polar solutes dissolve in polar solvents, and nonpolar solutes dissolve in nonpolar solvents.

What is viscosity?

A measure of a fluid's resistance to flow, which increases with stronger IMFs and lower temperature.

What are the endothermic phase changes?

Melting, boiling, evaporation, and sublimation.

What are the exothermic phase changes?

Freezing, condensation, and deposition.

What occurs during evaporation?

Only the highest-energy particles escape from a liquid below its boiling point, causing cooling.

How do molecular solutes behave in solution?

They dissolve as whole molecules and do not dissociate.

What happens to ionic solutes when they dissolve?

They dissociate into ions and can conduct electricity as electrolytes.

What is the difference between electrolytes and non-electrolytes?

Electrolytes are soluble ionic compounds that conduct electricity, while non-electrolytes are molecular compounds that do not.

What is the energy change when breaking solute bonds during dissolution?

It is an endothermic process.

What is the energy change when forming ion-dipole attractions during dissolution?

It is an exothermic process.

What is a characteristic of nonpolar molecules regarding intermolecular forces?

Nonpolar molecules only exhibit London Dispersion Forces (LDF).

How does soap function in terms of molecular structure?

Soap has a nonpolar 'tail' and a polar 'head'.

What are covalent network solids, and how do they behave in water?

Covalent network solids, like diamond, do not dissolve in water due to strong covalent bonds throughout.