Unit 3 Part 1 - Properties of Substances & Mixtures

Covers 3.1-3.6 on the College Board website :)

What are intermolecular forces?

It is weak attractions between covalent molecules that hold together a substance.

What affects how strong the interactions are between IMFs?

The partial charge of each molecule/ion, the overall size of the molecule, as well as the orientation of dipoles.

What is a dipole-dipole interaction?

It is when two or more polar molecules (have permanent dipoles) interact.

What is hydrogen bonding?

It is when a polar molecule that contains H bonded with NO or F interacts with another molecule containing H bonded with N1, O1, or F.

What is dipole induced?

When a polar and nonpolar with induced dipole interact.

Example: When a nonpolar and polar molecule come into contact, they now become polar. The electrons on one atom (from a molecule) will repel electrons in another molecule, making that second molecule go towards another atom in that second nonpolar molecule. (It makes one end in the nonpolar molecular more negative and the other more positive)

What are dipole ions?

An ion and a polar molecule (with a permanent dipole) interact.

What are London dispersion forces?

Experienced by ALL molecules (including nonpolar) due to Coulombic interactions between fluctuating dipoles. The larger the electron cloud, the more polarizable it is.

What are instantaneous dipoles?

Forms due to random movement of electrons within cloud

What is an induced dipole?

When a neighboring atom forms a temporary dipole after instantaneous dipole interactions with it.

This is when something isn’t polar BUT has an instantaneous dipole, it’s like a chain reaction.

Polar molecules can have (temporary/permanent) dipoles.

permanent

What kind of IMFs can polar molecules experience?

Dipole-Ion, Dipole-dipole, Hydrogen Bonding, London Dispersion Forces.

Nonpolar molecules can have (temporary/permanent) dipoles.

temporary

What types of IMFs can nonpolar molecules have?

London dispersion forces.

When can nonpolar molecules have stronger IMF interactions?

When they have large electron clouds or increased contact area between molecules.

When you have large biomolecules, what can happen between their IMFs?

They can experience IMFs between each other as well as different regions of the same large molecule. (think of Ethanol)

What is specific heat?

The amount of heat required to raise the temperature of a gram of something by 1 degree Celsius.

What molecules generally have a really high specific heat (name two)?

Ionic bonds and polar covalent molecules.

What is melting point?

The temperature at which a solid turns into a liquid.

What is the heat of vaporization?

The amount of heat required for a liquid to turn into a solid.

What is boiling point?

The temperature where vapor pressure and surrounding pressure match (all particles readily escape into the gas phase)

What is vapor pressure?

The pressure of vapor that is released by a liquid/solid in a closed container or space.

What happens to vapor pressure as the different IMFs become stronger?

The vapor pressure decreases (makes it harder to break apart).

Example: If you are boiling water with a lid over a bowl, it will be harder to break apart those water IMFs hence why you need more vapor pressure.

What is cohesion/adhesion?

It is the ability of molecules to “stick” to each other and other molecules.

What happens to cohesion/adhesion as the IMFs increase in strength?

The adhesion/cohesion becomes stronger.

What is solubility?

The ability of one substance to dissolve into another.

What happens if you have similar IMFs when dissolving them?

They become easier to dissolve with one another.

What are some common types of solids?

They include: Metals, Ceramics, Polymers, and Composites.

What are the different types of crystalline solids?

Ionic, Metallic, Molecular, and Network Covalent Solids.

Describe Ionic solids in terms of boiling point, conductivity, and brittleness/malleability :)

Boiling Point: It is very high and will break the bonds.
Conductivity: They are nonductive unless they are dissolved.
Brittleness/Malleability: They can have charges that offset, meaning they are hard and brittle.

Describe Metallic solids in terms of boiling point, conductivity, and brittleness/malleability :)

Boiling Point: It will break the bonds, but you don’t need much heat to do this.
Brittleness/Malleability: When broken, a delocalized sea of electrons allows for easy rearrangement when broken.
Conductivity: Very conductive because they have a delocalized sea of electrons.

Describe Molecular solids in terms of boiling point, conductivity, and brittleness/malleability :)

Boiling Point: It will break the IMFs (not the bonds)
Brittleness/Malleability: They can change based on whether or not the IMF breaks or reforms.
Conductivity: Not very conductive because each molecule has valence electrons tightly held to individual molecules.

What is a molecular solid?

When gasses are pushed down together to form a solid (dry ice).

Describe Network Covalent solids in terms of boiling point, conductivity, and brittleness/malleability :)

Boiling Point: It will break the bonds (not the IMFs) between atoms
Brittleness/Malleability: Every atom is bonded with localized electron clouds.
Conductivity: Not very conductive because each atom has tightly packed valence electrons.

What are Amorphous solids?

They are solids that cannot find its rearrangement and becomes something different when heated up. (like quartz)

What happens to noble gasses when you put them under crazy temperatures?

They become solids which have really weak IMFs (London Dispersion Forces).

What type(s) of bond(s) can typically exist under solids?

Ionic, Metalilc, Network Covalent, Molecular bonds.

What type(s) of bond(s) can typically exist under liquids?

Simple polar covalent molecules attracted by dipole-dipole and Simple nonpolar covalent molecules attracted by LDF.

What type(s) of bond(s) can typically exist under gases?

Simple nonpolar covalent molecules

How can you substitute the ideal gas law into finding density or exploring how density works?

D= MP/RT

What is Gay-Lussac’s Law?

States that temperature and pressure are proportional. As temperature goes up, pressure increases. 

What is Boyle’s Law?

States that as volume increases, pressure goes down

What is Charle’s Law?

States that as temperature increases, the volume increases.

When is Boyle’s law only true?

When nothing else, besides pressure and volume, are changing.

What is Dalton’s Law?

P_A+P_B+...+P_N=P_total

What is Dalton’s Law of Partial Pressure?

P_A=P_total*X_A

Where X_A = mol A/total mol

What is the Kinetic Molecular Theory?

It is the explanation behind all gas laws and assumes gasses are many tiny particles that are very far apart, constantly moving, and have no attraction/repulsion between each other.

What does Kinetic Molecular Theory NOT consider?

It does not consider LDFs or the volume of individual particles.

What does the Average Kinetic Energy of a Particle Equal?

KE=1/2mv²

m is the mass
v is the velocity

What does the Maxwell-Boltzmann Distribution Graph state?

It states that a sample of gas has molecules traveling at different speeds. We use the average speed.

According to that Maxwell-Boltzmann Distribution, what happens when the temperature is the same?

All gasses will have the SAME average kinetic energy.

List two things that are true about Kinetic Energy in terms of particles… Hint: think about their speed and their sizes.

All particles are moving at the same average speed.
Smaller particles will have higher average speeds.

When happens when you are diffusing/effusing particles?

More massive gas particles will move more slowly, evacuating the container or moving through a barrier more slowly.

Real gasses generally…

Have attractions and repulsions between particles - LDF or others (think vaporized water → still polar).

Real Gasses will behave closer to Ideal Gases when they:

• Are at high temperatures. They are moving too fast to interact much with other particles.

• Are at a low pressure. This means they are far apart so they don’t interact much with other particles.

• Are small, non-polar gas molecules. So, they don’t interact much with other particles.

Real Gasses will behave less Like Ideal Gases when they:

• Are at very low temperatures (particles will attract)

• Are at very high pressures (condensed particles volume starts to matter)

What are some polarity tips for seeing if something is polar (since you don’t know electronegativity).

• Florine w/ ANY nonmetal = polar

• N & O w/ any nonmetal = mostly polar

  • Exception if N and bonded with O (nonpolar)

• H w/any nonmetal = mostly polar

  • Exception is if H and C are bonded (nonpolar)