Unit 9

Kinetic molecular theory - What are two behaviors of gases based on particle size?

1. volume of the particles are negligible;

2. no significant attractive or repulsive forces

Kinetic molecular theory - What are two behaviors of gases based on particle motion?

1. elastic collisions;

2. gas particles are in constant, random motion

Kinetic molecular theory - What are two behaviors of gases based on particle energy?

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

2. While all particles have the same mass they travel at varying velocities

Do gases have high or low density in comparison to liquids and solids?

low - very spread out, high volume and low mass

What is diffusion?

gases go from an area of higher concentration to an area of lower concentration (smell of baking cookies)

What is effusion?

gases pass thru a microscopic opening from a higher concentration (helium balloon, flat tire)

What is 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? How do you know?

H - lighter in mass

What is pressure?

Force per unit area.

What is a barometer?

An instrument that measures atmospheric pressure

What is a manometer?

instrument used to measure gas pressure in a closed container

What is Dalton's Law of Partial Pressures?

Total pressure exerted by a mixture of gases is the sum of the pressures exerted independently by each gas in the mixture

What is the total pressure of the three gases if one is 15 atm, one is 10 atm and one is 25 atm?

50 atm (add them all together)

What are the three INTRAmolecular bonds?

covalent, ionic, metallic

Which INTRAmolecular bond is the strongest?

ionic

What does INTRA mean?

within (the compound)

What are the three INTERmolecular bonds/forces?

dispersion, dipole-dipole, hydrogen bonds

Which INTERmolecular force is the strongest?

Hydrogen bonds

Which INTERmolecular force is the weakest?

dispersion

Which INTERmolcular force is found in all molecules?

dispersion

Hydrogen bonds form between H and ...

FON

Which type of IMFA is found in nonpolar molecules?

dispersion

What type of IMFA(s) is/are found in polar molecules?

dispersion, dipole-dipole and/or Hydrogen bonds

How are dispersion forces formed?

from weak temporary dipoles that form as electrons shift around the nucleus

How are dipole-dipole forces formed?

polar molecules orient themselves so that oppositely charged regions align - think H-Cl as a polar molecule with different EN values

What could cause a weak dispersion force to get stronger?

larger molecules involved with greater mass and # of electrons, aka more dispersion forces

What molecule has stronger H-bonds? H2O or NH3 and why?

H2O - O has a greater electronegativity than N causing the bond to be stronger; this impacts what state the molecule is in at room temperature

What are the 2 general properties of liquids?

shape of the container, volume is definite or fixed

Are liquids compressible?

Not really - very little

What is viscosity?

a measure of a fluid's resistance to flow; viscosity increase = slower flow

How is the viscosity of a liquid determined?

by the strength of the IMFAs, size of the particle and the temperature of the substance

What is more viscose at the same temperature- water or honey?

Honey - stronger IMFAs

How can you reduce the viscosity of molasses?

Increase the temperature

What is surface tension?

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

What is cohesion?

an attraction between molecules of the same substance (mercury to itself)

What is adhesion?

An attraction between molecules of different substances (water to glass)

For food coloring to travel up a flower stem and dye the flower a different color which force needs to be stronger - adhesion or cohesion?

adhesion

What is capillary action?

"Capillary action occurs when a liquid rises in a thin tube because the adhesive forces between the tube and the liquid are stronger than the cohesive forces between liquid's molecules.

What are the two main characteristics of solids?

definite shape and volume

What is a covalent network solid?

A giant structure where atoms are covalently bonded together that is strong; macromolecule

What are some examples of covalent network solids?

carbon (diamond), silicon, aluminum nitride, silicon dioxide, quartz

What type of compound has the highest melting point?

covalent network solid

What type of compound has the lowest melting point?

nonpolar, especially those with lower masses

What are the three phase changes that require energy?

melting, evaporating, sublimating

What are the three phases changes that release energy?

freezing, condensating, deposition

Define melting point.

the temperature at which the IMFAs in a solid break and form a liquid

Define vaporization

the process by which a liquid changes to a gas

Define evaporation

Evaporation is the process by which liquid water becomes water vapor on the surface

Define vapor pressure

the pressure exerted by a vapor over a liquid

Define boiling point

the temperature at which the vapor pressure of a liquid equals the external or atmospheric pressure

What is sublimation?

the process in which a solid changes directly into a gas thus skipping the liquid phase

What are some substances that sublimate?

dry ice, moth balls, ice cubes, solid iodine

Define freezing point

The temperature at which a liquid changes into a solid

Define condensation

When a gas turns into a liquid

What is deposition?

When a gas turns into a solid without becoming a liquid first

What is a phase diagram?

diagram that shows the phase of a substance based upon the temperature and pressure conditions

Define triple point

the temperature and pressure where liquid, solid, and gas are equally stable and are in equilibrium

Define critical point

the critical temperature and pressure above which the substance cannot exist as a liquid

If the vapor pressure increases what happens with the temperature of the gas?

increases

If IMFAs increase... what happens to the vapor pressure and temperature?

decreases

If a substance is more adhesive than cohesive what type of meniscus forms?

concave up (like a u)

If a substance is more cohesive than adhesive what type of meniscus forms?

concave down (frowny face)

What state of matter is represented by A?

solid

What does dot "d" represent?

critical point

What does dot "b" represent?

triple point

What phase is in the "g" area?

liquid

What are some examples of covalent network substances?

diamonds, silicon, aluminum nitride, carbon, silicon monocarbide, quartz,

What is volatility?

The tendency to turn into a gas

If a substance has high volatility what does it have strong or weak IMFAs?

weak

Which type of force is stronger in this picture: Adhesive or cohesive?

adhesive

What phenomena is occurring in this picture?

surface tension

Which type of force is stronger in this picture to the left: Adhesive or cohesive?

cohesive

What is happening in this picture?

capillary action

If there is high surface tension are IMFA's strong or weak?

strong

Which one has a higher boiling point - polar molecule or ionic compound?

ionic compound

Which one has a higher boiling point - NH3 or CF4?

NH3 - polar, hydrogen bonds

Which one has a higher melting point - MgCl2 or SiC?

SiC - covalent network

Which type of IMFA requires the most amount of energy to break it?

hydrogen bonds

What type of IMFAs have the lowest viscosity?

dispersion

Under what two "conditions" does viscosity increase?

stronger IMFAs and larger particles

What happens to atmospheric pressure with the BP increases?

also increases

Is the boiling point of a substance great on top of a mountain, sea side, or at the great barrier reef?

great barrier reef

If the BP increases what is likely happening with IMFAs?

strength is increasing

What is vapor pressure equal to?

atmospheric pressure