intermolecular forces, aqueous solutions

Intermolecular forces exist between molecules and their effects are seen everywhere.

What are intermolecular forces and where are their effects seen?

Intermolecular bonds create the surface tension that allows insects to walk on water.

How do intermolecular forces affect surface tension?

Intermolecular forces are 10 - 100 times weaker than strong intramolecular forces such as ionic, metallic, and covalent bonds.

How do intermolecular forces compare in strength to intramolecular forces?

Vapor pressure is the pressure that gaseous molecules exert on the walls of a closed container when the rates of evaporation and condensation become equal.

What is vapor pressure?

Liquids with stronger intermolecular forces have lower vapor pressures.

How does the strength of intermolecular forces relate to vapor pressure?

As temperature increases, vapor pressure increases because a greater proportion of particles have enough kinetic energy to escape the liquid.

What happens to vapor pressure as temperature increases?

The boiling point is the temperature at which a liquid's vapor pressure reaches the atmospheric pressure of the surroundings.

What is the boiling point (BP) of a liquid?

In a liquid with strong intermolecular forces, molecules are held tightly together, making it harder for them to escape, resulting in lower vapor pressure.

What is the relationship between intermolecular forces and the escape of molecules from a liquid?

Electronegativity is the tendency of an atom in a covalent bond to attract electrons.

What is electronegativity?

Electronegativity increases across a period and decreases down groups.

How does electronegativity change across a period and down groups?

A non-polar covalent bond occurs when two atoms in a covalent bond are the same, resulting in equal sharing of electrons.

What defines a non-polar covalent bond?

An electric dipole is the separation of positive and negative charges in a molecule, creating oppositely charged poles.

What is an electric dipole?

The greater the difference in electronegativities between two atoms, the greater the polarity of the covalent bond.

How does the difference in electronegativities affect bond polarity?

The polarity of polyatomic molecules depends on the shape of the molecule and the polarity of the covalent bonds.

What determines the polarity of polyatomic molecules?

The three main types of intermolecular forces are dipole-dipole, hydrogen bonding, and dispersion forces.

What types of intermolecular forces exist?

Dipole-dipole forces occur only in polar molecules and result from the attraction between the positive and negative ends of polar molecules.

What are dipole-dipole forces?

Hydrogen bonds occur between molecules where hydrogen is bonded to nitrogen, oxygen, or fluorine (NOF).

What are hydrogen bonds and when do they occur?

The presence of hydrogen bonds results in higher melting and boiling points.

What is the significance of hydrogen bonding in terms of melting and boiling points?

Dispersion forces are the forces of attraction between non-polar molecules caused by temporary dipoles due to random electron movement.

What are dispersion forces?

The strength of dispersion forces increases as the size of the molecule increases due to a larger number of electrons.

How does the size of a molecule affect dispersion forces?

Molecules that form long chains tend to have stronger dispersion forces than more compact molecules with a similar number of atoms.

What is the relationship between molecular shape and dispersion forces?

Polar substances tend to dissolve in polar solvents, while non-polar substances dissolve in non-polar solvents.

How do polar and non-polar substances interact with solvents?

Asymmetrical molecules are polar because their individual dipoles do not cancel out, resulting in a net dipole.

What is the effect of asymmetry on molecular polarity?

Partial charges on polar molecules add to give a total charge of zero and are smaller than the charges on ions.

How do partial charges on polar molecules compare to charges on ions?

Stronger intermolecular forces require more energy to break bonds and change state, influencing melting and boiling points.

What is the impact of intermolecular forces on the properties of substances?