c2

Question 1

name the limitations of the particle model

Answer 1

1. All particles are represented as spheres
2. Particles are represented solid and unbreakable
3. We simplify the different forces between particles by calling them all bonds

Question 2

what happens when when a liquid reaches boiling point

Answer 2

particles have enough energy to overcome forces

Question 3

name the two main types of covalent structures

Answer 3

1. simple molecules
2. giant covalent structures

Question 4

describe simple molecules

Answer 4

• low boiling point and melting point
• molecules held together by weak intermolecular forces
• covalent bonds between atoms

Question 5

describe giant covalent structures

Answer 5

high boiling point and melting point due to strong covalent bonds which hold the structure together

Question 6

why does carbon dioxide have a low boiling point

Answer 6

• carbon dioxide is a simple molecule
• there are weak intermolecular forces
• therefore a small amount of energy is needed to overcome these forces

Question 7

why does diamond have a high melting point?

Answer 7

• diamond is a giant covalent structure
• there are strong covalent bonds between the carbon atoms
• therefore a large amount of energy is needed to overcome the bonds.

Question 8

describe the structure of diamond

Answer 8

each carbon atom forms four covalent bonds with other carbon atoms

Question 9

describe the structure of graphite

Answer 9

each carbon atom forms three covalent bonds with other carbon atoms forming layers of hexagonal rings

Question 10

can diamond conduct electricity? why?

Answer 10

no

no delocalised electrons

Question 11

why is graphite soft

Answer 11

soft due to weak intermolecular forces between layers of carbon so layers can slide off

Question 12

can graphite conduct electricity? why?

Answer 12

yes

delocalised electrons move between layers carrying charge to conduct electricity

Question 13

describe the structure of sodium chloride

Answer 13

sodium chloride consists of sodium and chloride ions arranged in a giant ionic lattice. the ions are held together by strong electrostatic forces of attraction between positive and negative ions

Question 14

why do ionic compounds have high melting points?

Answer 14

high electrostatic forces of attraction between ions so high amounts of energy needed to overcome these forces

Question 15

when can ionic compounds conduct electricity

Answer 15

ionic compounds can conduct electricity when molten or dissolved because the electrostatic forces are overcome so ions are separated so they are free to move within the structure and carry charge

Question 16

describe the structure of a metal

Answer 16

• atoms arranged in regular structure
• positive metal ions
• with a sea of delocalised electrons
• strong electrostatic forces of attraction between these hold the structure together

Question 17

why can metals conduct electricity

Answer 17

have delocalised electrons which can move through structure and carry current

Question 18

why are metals malleable and ductile

Answer 18

layers slide over each other and therefore can form new shapes

Question 19

what is an alloy

Answer 19

alloys are mixtures of two or more elements, one of which is a metal

Question 20

why are alloys stronger than pure metals

Answer 20

• they have different sized atoms
• so layers are distorted
• can’t cannot slide over eachother as easily