C3 - Structure and Bonding

Question 1

Ionic Compound properties

Answer 1

• High melting and boiling points due to strong electrostatic forces of attraction between ions
• Do not conduct electricity as ions are fixed
• When melted or dissolved in water they conduct electricity as ions are free to move
• Dissolve easily one water and ions separate

Question 2

What kind of atoms form ionic bonds

Answer 2

Metals and Non-metals

Question 3

What kind of atoms form covalent bonds

Answer 3

non-metals

Question 4

Properties of simple molecular covalent substances

Answer 4

• Low melting and boiling points as there are weak inter-molecular forces are needed to be broken, not covalent bonds
• As molecule gets bigger, melting and boiling points increase as strength of molecular forces increases
• Don’t conduct electricity as they are not charged and there are no free electrons or ions

Question 5

What are polymers and how are they held together

Answer 5

Large molecules consisting of lots of small units linked together by strong covalent bonds to form a long molecule with repeating units.

Question 6

Properties of Polymers

Answer 6

• Higher melting and boiling point than simple molecular substances as intermolecular forces between molecules are stronger
• Solid at room temperature
• However, intermolecular forces weaker than ionic or covalent bonds so they have lower boiling points than ionic or giant molecular compounds

Question 7

Giant Covalent Structures Properties

Answer 7

• Very high melting and boiling points as strong covalent bonds between atoms
• Don’t conduct electricity as don’t contain charged particles (graphite is exception)

Question 8

Properties of Diamond

Answer 8

• Made up of carbon atoms that form four covalent bonds. this makes diamond very hard
• Very high melting point as strong covalent bonds
• No free electrons or ions so doesn’t conduct electricity

Question 9

Properties of graphite

Answer 9

• Each carbon atom only forms 3 covalent bonds. So there are no covalent bonds between layers so they’re held together weakly and are free to slide over each other which makes graphite soft and slippery - ideal lubricating material
• High melting point of covalent bonds in layers need lots of energy to break
• Only 3 out of 4 of carbon’s outer electrons used in bonds so each atom has a delocalised electron that allow graphite to conduct thermal energy and electricity

Question 10

What is graphene and it’s properties

Answer 10

• A single layer of graphite
• one atom thick
• network of covalent bonds make it very strong and light
• contains delocalised electrons so can conduct electricity

Question 11

Uses of graphene

Answer 11

• Used in electronics

* Added to composite materials to improve strength without adding much weight

Question 12

What are Fullerenes

Answer 12

Molecules of carbon shaped like closed tubes or hollow balls and are made mainly of carbon atoms arranged in hexagons with some rings of 5 or 7 atoms

Question 13

What is the Buckminsterfullerene

Answer 13

the first fullerene discovered (C60) a hollow sphere containing 20 hexagons and 12 pentagons

Question 14

Uses of fullerenes

Answer 14

• Used to ‘cage’ other molecules as the structure forms around another molecule or atom. This could be used to deliver a drug into the body
• Huge surface area could make them good industrial catalysts if individual catalyst molecules are attached to fullerenes

Question 15

What are carbon nanotubes

Answer 15

Cylindrical fullerenes with very high length to diameter ratios

Question 16

Properties and uses of nanotubes

Answer 16

• Can conduct thermal energy and electricity
• High tensile strength (don’t break when stretched)
• Used in technology (nanotechnology)
• Used in electronics or to strengthen materials without adding weight (eg in tennis racket frames)

Question 17

What are properties of metals

Answer 17

• Electrostatic forces of attraction are strong so compounds with metallic bonds have very high melting and boiling points
• Delocalised electrons can carry charge through metal so metals are good conductors of electricity and heat

Question 18

How big are nanoparticles

Answer 18

they have a diameter of between 1nm and 100nm and have a high surface area to volume ratio

Question 19

Uses of nanoparticles

Answer 19

• Large SA to volume ratio makes them good catalysts
• Fullerenes could be used to deliver drugs to places in the body
• some Can conduct electricity so can be used in tiny electric computers
• Silver nanoparticles have antibacterial properties so can be added to polymer fibres to make surgical masks and wound dressings. they can also be added to deodorants
• Used in cosmetics
• Used in suncreams as they have better skin coverage so more effective protection from suns rays

Question 20

Disadvantages of nanoparticles

Answer 20

• Ways they affect the body aren’t fully understood
• Might damage cells if they get into body
• When washes away might damage environment