Unit 9

Kinetic Molecular Theory

The theory that explains the behaviors of gases based on particles' size, motion, and energy.

Volume of gas particles

Negligible; they take up minimal space in a gas.

Attractive forces in gases

No significant attractive or repulsive forces between gas particles.

Elastic collisions

Collisions where gas particles bounce off each other without losing kinetic energy.

Particle motion in gas

Gas particles are in constant, random motion.

Particle energy and temperature

Particle energy is directly related to the temperature of the gas.

Gas particle velocities

Gas particles travel at varying velocities despite having the same mass.

Gas density

Low density compared to liquids and solids due to large volume and low mass.

Diffusion

The process where gases move from higher concentration to lower concentration.

Effusion

The process where gases pass through a microscopic opening from higher concentration.

Graham's Law of Effusion/Diffusion

The rate of effusion/diffusion for a gas is inversely proportional to the square root of its molar mass.

Which gas travels faster, H or He?

H travels faster because it is lighter in mass.

Pressure

Force exerted per unit area.

Barometer

An instrument that measures atmospheric pressure.

Manometer

An instrument used to measure gas pressure in a closed container.

Dalton's Law of Partial Pressures

Total pressure exerted by a mixture of gases is the sum of each gas's pressures.

Total pressure calculation

Total pressure is found by adding pressures (e.g., 15 atm + 10 atm + 25 atm = 50 atm).

Three types of intramolecular bonds

Covalent, ionic, metallic.

Strongest intramolecular bond

Ionic bond.

Meaning of INTRA

Within (the compound).

Three types of intermolecular bonds/forces

Dispersion, dipole-dipole, hydrogen bonds.

Strongest intermolecular force

Hydrogen bonds.

Weakest intermolecular force

Dispersion forces.

Intermolecular force found in all molecules

Dispersion forces.

Hydrogen bonds form between H and…

FON (Fluorine, Oxygen, Nitrogen).

Intermolecular force in nonpolar molecules

Dispersion forces.

Intermolecular forces in polar molecules

Dispersion, dipole-dipole, and/or Hydrogen bonds.

Formation of dispersion forces

From weak temporary dipoles as electrons shift around the nucleus.

Formation of dipole-dipole forces

Occurs when polar molecules align oppositely charged regions.

Factors strengthening weak dispersion forces

Larger molecules with greater mass and more electrons.

Stronger H-bonds: H2O or NH3?

H2O due to greater electronegativity of O compared to N.

Two general properties of liquids

Definite volume and shape of the container.

Compressibility of liquids

Not compressible; very little change in volume.

Viscosity

A measure of a fluid's resistance to flow; increased viscosity means slower flow.

Determination of liquid viscosity

By strength of IMFAs, particle size, and temperature.

More viscous substance at the same temp: water or honey?

Honey due to stronger IMFAs.

Reducing viscosity of molasses

Increase the temperature.

Surface tension

The energy required to increase the surface area of a liquid by a given amount.

Cohesion

Attraction between molecules of the same substance.

Adhesion

Attraction between molecules of different substances.

Force needed for food coloring to travel up a flower stem

Stronger adhesion forces.

Capillary action

Occurs when liquid rises in a thin tube due to stronger adhesive forces than cohesive forces.

Two main characteristics of solids

Definite shape and volume.

Covalent network solid

A giant structure where atoms are covalently bonded, forming a strong macromolecule.

Examples of covalent network solids

Diamond, silicon, aluminum nitride, silicon dioxide, quartz.

Compound with highest melting point

Covalent network solid.

Compound with lowest melting point

Nonpolar compounds, especially those with lower masses.

Phase changes requiring energy

Melting, evaporating, sublimating.

Phase changes releasing energy

Freezing, condensating, deposition.

Melting point

The temperature at which a solid becomes a liquid.

Vaporization

The process where a liquid changes to a gas.

Evaporation

The process where liquid water becomes vapor at the surface.

Vapor pressure

The pressure exerted by a vapor over a liquid.

Boiling point

The temperature when vapor pressure equals external pressure.

Sublimation

The process where a solid changes directly to gas, skipping the liquid phase.

Substances that sublimate

Dry ice, mothballs, ice cubes, solid iodine.

Freezing point

The temperature at which a liquid turns into a solid.

Condensation

A gas changing into a liquid.

Deposition

A gas turns into a solid without becoming liquid first.

Phase diagram

Diagram showing the phase of a substance based on temperature and pressure.

Triple point

Temperature and pressure where liquid, solid, and gas are equally stable.

Critical point

Condition above which a substance cannot exist as a liquid.

Vapor pressure increase effect on gas temperature

Temperature of the gas increases.

IMFA increase effect on vapor pressure and temperature

Decreases vapor pressure and temperature.

Meniscus formation with strong adhesion

Concave up (like a U).

Meniscus formation with strong cohesion

Concave down (frowny face).

State of matter represented by A

Solid.

What does dot 'd' represent?

Critical point.

What does dot 'b' represent?

Triple point.

Phase in the 'g' area

Liquid.

Examples of covalent network substances

Diamonds, silicon, aluminum nitride, carbon, silicon monocarbide, quartz.

Volatility

The tendency of a substance to turn into a gas.

High volatility indicates strong or weak IMFAs?

Weak IMFAs.

Which force is stronger: Adhesive or cohesive?

Adhesive (in specific scenarios).

Phenomenon occurring in the picture

Surface tension.

Which force is stronger: Adhesive or cohesive on the left?

Cohesive.

Phenomenon in the picture

Capillary action.

High surface tension indicates strong or weak IMFAs?

Strong IMFAs.

Higher boiling point: polar molecule or ionic compound?

Ionic compound.

Higher boiling point: NH3 or CF4?

NH3 (polar, hydrogen bonds).

Higher melting point: MgCl2 or SiC?

SiC (covalent network).

IMFA requiring the most energy to break

Hydrogen bonds.

IMFA with the lowest viscosity

Dispersion forces.

Conditions that increase viscosity

Stronger IMFAs and larger particles.

Effect on atmospheric pressure when boiling point increases

Atmospheric pressure also increases.

Boiling point environment comparison

Great Barrier Reef (higher than on a mountain or seaside).

Effect on IMFAs when boiling point increases

Strength of IMFAs likely increases.

What is vapor pressure equal to?

Atmospheric pressure.