Chemistry - Chapter 11

What is kinetic energy?

Energy due to motion.

What does the kinetic molecular theory describe?

It describes the behavior of matter in terms of particles in motion.

What are the assumptions of the kinetic molecular theory?

1. All matter is composed of tiny particles. 2. Particles of a gas are in continual motion. 3. Collisions between gas particles and container walls are elastic. 4. No force of attraction or repulsion between gas particles. 5. Average kinetic energy depends on temperature.

What is an elastic collision?

A collision in which there is no net loss of kinetic energy.

How does temperature affect the average kinetic energy of gas particles?

The average kinetic energy increases with increasing temperature.

What happens to the speed of lighter gas particles compared to heavier ones at the same temperature?

Lighter gas particles have higher average speeds than heavier gas particles.

What is the formula for kinetic energy (KE)?

KE = 1/2 mv², where m is mass and v is velocity.

What does temperature measure in a sample of matter?

Temperature is a measure of the average kinetic energy of the particles.

What conditions allow gases to behave nearly ideally?

Gases behave nearly ideally if pressure is not very high and temperature is not very low.

List one physical property of gases related to expansion.

A gas will fill any size or shaped container.

What is fluidity in gases?

Due to weak attraction forces, gases have the ability to flow.

How does the density of gases compare to solids and liquids?

A gas's density is 1/1000th the density of the solid and liquid state.

What is compressibility in gases?

The volume of a gas sample can be decreased many times.

Define diffusion in the context of gases.

The spontaneous spreading of a gas to occupy a space.

What is effusion?

The process by which gas particles under pressure pass through a tiny opening.

What are the properties of liquids?

Liquids have no definite shape, a definite volume, fluidity, high density, incompressibility, dissolving ability, diffusion, surface tension, and capillary action.

What is the kinetic molecular theory (KMT) description of liquids?

Liquids have no definite shape, are in constant motion, have particles that are closer together and lower in energy than gas particles, and have stronger attractive forces than gases.

What are the types of intermolecular forces in liquids?

Dipole-dipole forces, dispersion forces, and hydrogen bonds.

What are dipole-dipole forces?

Attractions between oppositely charged regions of polar molecules.

What are dispersion forces?

Weak forces resulting from temporary shifts in the density of electrons in electron clouds.

What are hydrogen bonds?

Special dipole-dipole attractions that occur between molecules containing a hydrogen atom bonded to a small, highly electronegative atom with at least one lone electron pair.

What is fluidity in liquids?

The ability of liquids to flow because their particles are not bound together in fixed positions.

Why do liquids have high density?

Due to the closeness of particles, liquids are only about 10% less dense than solids.

What does incompressibility mean in the context of liquids?

Liquid particles are closely packed, making them only about 4% compressible.

What is the dissolving ability of liquids?

Liquids are the most common dissolving agents, and if only one physical state is observed after mixing, one substance is said to have dissolved.

How does diffusion occur in liquids?

Liquids will diffuse much slower than gases due to the closeness of the particles, and the diffusion rate increases with temperature.

What is surface tension in liquids?

An attractive force that pulls the molecules at a liquid's surface together, forming a sort of skin.

Why do liquid droplets take on a spherical shape?

Because a sphere has the smallest possible surface area.

What is capillary action?

The attraction of the surface of a liquid to the surface of a solid.

What is the least common state of matter?

Liquids.

What range of conditions do liquids exist in?

Liquids can only exist within a relatively narrow range of temperatures and pressure.

How do the attractive forces of liquids compare to those of gases?

The attractive forces of liquids are stronger than those of gases.

What happens to the diffusion rate of liquids with temperature?

The diffusion rate increases with temperature.

What is the significance of the closeness of liquid particles?

It contributes to properties such as high density, incompressibility, and slower diffusion.

What is the relationship between liquid particles and energy compared to gas particles?

Liquid particles have lower energy than gas particles.

Evaporation

many liquids will spontaneously vaporize

Vaporization

process in which a liquid or solid changes into a gas

Evaporation

process in which molecules leave the surface of a nonboiling liquid

Will solidify

if cooled enough for the attraction forces to hold the molecules in a fixed position

Melting

The melting point of a crystalline solid is the temperature at which the forces holding the crystal lattice together are broken, and the crystalline solid becomes a liquid.

Vaporization

Vaporization is the process by which a liquid changes to a gas or vapor.

Evaporation

Evaporation is vaporization that occurs only at the surface of a liquid.

Equilibrium vapor pressure (evp)

The pressure exerted by a vapor in equilibrium with its liquid at a given temperature.

Volatile liquids

Volatile liquids are liquids that evaporate readily and have relatively weak forces of attraction between their particles.

Nonvolatile liquids

Nonvolatile liquids do not evaporate readily and have relatively strong attractive forces between their particles.

Boiling

Boiling is the conversion of a liquid to a vapor within the liquid as well as at its surface.

Boiling point

The temperature at which the e.v.p. of the liquid is equal to the atmospheric pressure.

Sublimation

Sublimation is the process by which a solid changes directly to a gas without first becoming a liquid.

Freezing

The freezing point is the temperature at which a liquid is converted into a crystalline solid.

Condensation

The process by which a gas or a vapor becomes a liquid.

Deposition

Deposition is the process by which a substance changes from a gas or vapor to a solid without first becoming a liquid.

Equilibrium Vapor Pressure of a Liquid

Every liquid has a specific equilibrium vapor pressure at a given temperature.

Atmospheric pressure

The pressure exerted by the weight of the atmosphere, typically measured at 760 mm Hg.

Endothermic process

A process that absorbs energy from its surroundings.

Exothermic process

A process that releases energy to its surroundings.

Kinetic energy

The energy possessed by an object due to its motion.

Strong attraction forces

Forces that hold liquid molecules closely together, resulting in low vapor pressure.

Weak attraction forces

Forces that allow liquid molecules to escape easily into the vapor phase, resulting in high vapor pressure.

Which phase changes are exothermic?

freezing, condensation, deposition

Which phase changes are endothermic?

melting, vaporization, sublimation

Phase diagrams

Graphs that show the phase behavior of a substance at different temperatures and pressures, illustrating regions of solid, liquid, and gas.

Triple point

the temperature and pressure where all three phases (solid, liquid, gas) coexist in equilibrium.

Critical point

Indicates the critical temperature and critical pressure

Critical Temperature

the highest temperature at which a substance can exist as a liquid, regardless of pressure.

Critical Pressure

the minimum pressure required to liquefy a substance at its critical temperature.