Liquids And Solids

Question 1

Chemical changes

Answer 1

Involve changes to the compounds chemical formula or structure, and they will usually yield different products

Question 2

Physical changes

Answer 2

Do NOT involve changes to the compounds chemical structure, and will usually yield the same compound as a product

Question 3

How to calculate vapor pressure of a solution when a solute is added?

Answer 3

Use Raoult’s law: P_solution = X_solvent x P_pure

P_solution = The solutions new vapor pressure once the solute is added
X_solvent = percentage of solvent in the solution (or mole fraction of solvent)
P_pure = vapor pressure of the solvent when its pure

Question 4

Intermolecular forces

Answer 4

Forces that attract molecules to each other
The stronger the intermolecular forces, the more intensely molecules are attracted to each other and they “stick” together

Question 5

What do high intermolecular forces lead to?

Answer 5

High boiling point
High heat of vaporaization
High viscosity
High surface tension
Low vapor pressure

Question 6

Melting points of molecules that have similar molecular weights:

Answer 6

The stronger the intermolecular forces, the higher the boiling point
Strongest to weakest:
Hydrogen bonding
Dipole-dipole
London dispersion forces

Question 7

Dipole-dipole intermolecular forces

Answer 7

Occurs in molecules that are polar (net nonzero dipole moment)
Does NOT apply to ionic compounds only to molecular (all nonmetals) compounds

Generally, any two atoms that are different from each other, other than C and H, there will be a dipole-dipole interaction

Question 8

Crystalline solids

Answer 8

• Long range order
• There is a consistent, crystal lattice network of atoms that is well defined, and repeated throughout the structure which causes them to have sharp, well-defined, characteristic melting temperatures and break with a cleavage along a very straight plate

Question 9

Amorphous solids

Answer 9

• Short range order
• No consistent structure of atoms throughout the solid which leads to a broad range of melting temperatures for any given amorphous solid, and they have irregular breakage patterns

Question 10

What do pure diatomic elemental gases have very low melting points?

Answer 10

Pure gases are purely covalently bonded and non-polar due to the even sharing of electrons, therefore they have weak intermolecular forces resulting in the very low melting point

Ex: O₂, N₂

Question 11

Boiling point of water at higher elevations:

Answer 11

Boiling point will be lower than at sea level because there is less atmospheric pressure