1.3 - compounds and bonding

Question 1

when do non-polar (pure covalent bonds) form?

Answer 1

if the difference in electronegativity is less than 0.4

Question 2

when does polar bonding occur?

Answer 2

if the difference in electronegativity is between 0.5 and 1.9

Question 3

how do you actually determine if something is polar?

Answer 3

if a line can be drawn through the molecule to separate the positive end from the negative end

Question 4

which end of a molecule is positive?

Answer 4

the end with the lowest electronegativity

Question 5

which end of a molecule is negative?

Answer 5

the end with the greatest electronegativity

Question 6

is carbon dioxide polar or non-polar?

Answer 6

• non-polar
• O=C=O

Question 7

how can polar liquids be identified?

Answer 7

polar substances are deflected by a charged rod

Question 8

intermolecular

Answer 8

found between molecules

Question 9

intramolecular

Answer 9

covalent bonding within a molecule (never breaks)

Question 10

what are the three types of intermolecular attractions (van der waal’s forces)?

Answer 10

• london dispersion forces
• permanant dipole - permanent dipole interactions
• hydrogen bonding

Question 11

what are the features of london dispersion forces?

Answer 11

• present between all molecular/ monatomic
• only controls non-polar/monatomic substances properties

Question 12

what is the weakest type of van der waal force?

Answer 12

london dispersion forces

Question 13

the more electrons there are in an atom or molecule…?

Answer 13

the stronger the london dispersion forces

Question 14

what are london dispersion forces?

Answer 14

an attraction which arises between a temporary dipole and a temporarily induced dipole caused by an unequal distrubution of electrons

Question 15

what do permanent dipole - permanent dipole interactions occur between?

Answer 15

polar molecules/substances

Question 16

what is a permanent dipole - permanent dipole interaction?

Answer 16

the attraction between a permanent dipole in one molecule and a permament dipole in a neighbouring molecule

Question 17

what is hydrogen bonding?

Answer 17

a special type of permanent dipole - permanent dipole interaction involving molecules where hydrogen is directly bonded to nitrogen, oxygen or fluorine within a molecule

Question 18

carbon to hydrogen bonds are always what?

Answer 18

non-polar

Question 19

what happens as the size of non-polar molecules increase?

Answer 19

as the size of the molecules increase, the number of electrons increases, the greater the strength of the london dispersion forces

Question 20

what do ionic substances dissolve in and why?

Answer 20

• polar solvents
• the strength of ionic bonding is compatible with the hydrogen bonding between water molecules

Question 21

what is the phrase to remember regarding solubility?

Answer 21

like dissolves like

Question 22

why do non-polar substances not dissolve in water?

Answer 22

as L.D.Fs are not compatible with the hydrogen bonding found in water

Question 23

what do non-polar substances dissolve in?

Answer 23

non-polar solvents which have L.D.Fs present

Question 24

what are polar substances which do not have hydrogen bonding present less likely to be soluble in and why?

Answer 24

• water
• as their permanent dipole attractions are not compatible with hydrogen bonding found in water

Question 25

what polar substances will dissolve in water?

Answer 25

only polar substances which can form hydrogen bonds with water molecules will dissolve in water

Question 26

what are the only compounds that will dissolve in water?

Answer 26

only ionic compounds and polar covalent compounds (which can hydrogen bond with water molecules) will dissolve in water

Question 27

what is viscosity?

Answer 27

the viscosity of a liquid is a measure of how thick the liquid is

Question 28

the more hydroxyl (OH) groups present in the molecule…?

Answer 28

the stronger the hydrogen bonding will be between the molecules, the more visocus the liquid will be

Question 29

what are the five features of ionic compounds?

Answer 29

• giant lattice structure of ions
• electrostatic forces of attraction between ions
• high melting point and boiling point
• conducts electricity when in solution or molten
• often soluble in water (polar solvent) and insoluble in non-polar, covalent

Question 30

what are the five features of covalent molecular substances?

Answer 30

• discrete molecules
• very weak L.D.Fs or weak hydrogen bonds between molecules
• low melting and boiling point
• non conducting
• often soluble in non-polar organic solvents

Question 31

what are the four features of covalent network substances?

Answer 31

• (usually) 3D giant network with covalent bonds between atoms
• high melting and boiling points
• non conducting
• tend to not be soluble