chapter 6

Question 1

what is electronegativity

Answer 1

• a measure of the ability of an atom in a molecule to attract a pair of electrons in a covalent bond to itself
• it increases as you go up a group and across a period

Question 2

what is a non polar bond

Answer 2

• the bonded pair of electrons are shared equally between the bonded atoms
  it occurs when:
• the bonded atoms are the same
• the bonded atoms have very similar electronegativity values

Question 3

what is a polar bond

Answer 3

• the bonded electrons are shared equally between the bonded atoms
• they occur when the electronegativity values are different
• they have a partial charge which creates a dipole

Question 4

what are polar molecules

Answer 4

• the dipoles don’t cancel eachother out
• they are not symmetrical
• they have polar bonds

Question 5

explain solubility and water

Answer 5

• water can form strong enough attractions to the ions to allow them to dissolve
• water can dissolve many ionic compounds

Question 6

what are intermolecular forces

Answer 6

• weak interactions between different molecules
• they are largely responsible for the properties of covalent molecules

Question 7

how do induced dipole dipole interactions form

Answer 7

• also called london forces
• the strength is determined by how many electrons the molecule contains
• they are only temporary
• all electrons are constantly moving
• a temporary uneven distribution of charge creates an instantaneous dipole
• this induces a dipole in the neighboring electrons
• this leads to an attraction

Question 8

explain permanent dipole dipole interactions

Answer 8

• they only occur in polar molecules
• they are permanent and do not come and go

Question 9

what are simple molecular substances

Answer 9

• they are substances containing a specific number of atoms and they have a consistent molecular formula
• they are arranged in a simple lattice
• they are held together by weak intermolecular forces
• the atoms within each molecule are held by strong covalent bonds

Question 10

describe the melting and boiling point of simple molecular substances

Answer 10

• they are relatively low
• they do not need much energy to overcome the weak intermolecular forces

Question 11

describe the solubility of simple molecular substances

Answer 11

• non polar molecules tend to dissolve in non polar solvents
• polar molecules tend to dissolve in polar solvents

Question 12

explain electrical conductivity in simple molecular substances

Answer 12

• they do not conduct any electricity

Question 13

what are hydrogen bonds

Answer 13

• a special type of permanent dipole dipole interactions
  they contain:
• an electronegative atom, with a lone pair of electrons
• oxygen, nitrogen, fluorine
• a hydrogen atom bonded to the electronegative atom

Question 14

what are the anomalous properties of water

Answer 14

• the solid is less dense than the liquid
• water has a relatively high melting and boiling point
• water has a relatively high surface tension

Question 15

explain why ice is less dense than water

Answer 15

• the hydrogen bonds hold the water molecules further apart in an open lattice structure
• the water molecules in ice are further apart than in water
• this makes ice less dense than water

Question 16

explain why water has a high melting and boiling point

Answer 16

• it can form extensive hydrogen bonds which are the strongest intermolecular force

Question 17

why does water have a high surface tension

Answer 17

• the molecules on the surface experience unbalanced hydrogen bonds
• this pulls them in which increases the surface tension

Question 18

explain the structure of DNA

Answer 18

• a double helix structure held together by hydrogen bonds between base pairs