bonding, structure and properties

Question 1

what is a compound?

Answer 1

substance in which two or more elements are chemically combined

Question 2

what are the three types of chemical bonds?

Answer 2

• ionic
• covalent
• metallic

Question 3

what is the bonding and structure like in iconic compound?

Answer 3

• bonding occurs between metals and non-metals
• electrostatic attractions between oppositely charged ions
• form a giant ionic lattice
• electrons are transferred [metals lose, non-metals gain]

Question 4

what’s the diagram for ionic bonding?

Answer 4

[o]+ [o]-

Question 5

what are the properties of an ionic compound?

Answer 5

• high melting and boiling points
• only conduct electricity when molten/dissolved
• brittle

Question 6

what is the bonding and structure like in metallic compounds?

Answer 6

• giant structures of positive metal ions
• electrons in outer shell are delocalised [free to move through the whole structure]
• electrostatic attraction between positive metal ions and negative delocalised electrons

Question 7

what are the properties of metallic compounds?

Answer 7

• layers can slide over each other, they can be bent [malleable and ductile]
• delocalised electrons so they can carry charge, can conduct electricity and heat
• bonds are very strong, high melting and boiling points

Question 8

what is the bonding like in covalent bond?

Answer 8

• atoms share electrons

Question 9

what’s the diagram for covalent bonding?

Answer 9

venn diagram thing

Question 10

what are the properties of simple molecules?

Answer 10

• usually gasses or liquids that have low melting and boiling points
• weak intermolecular forces
• don’t conduct electricity

Question 11

what are the properties of giant covalent structures?

Answer 11

• solids
• very high melting and boiling points
• strong covalent bonds

Question 12

what are the properties of diamond?

Answer 12

• each carbon atom is covalently bonded to 4 other carbon atoms
• very hard
• very high melting point
• doesn’t conduct electricity

Question 13

what is an allotrope?

Answer 13

different forms elements can exist in - the structures are made up of the same element, yet don’t have the same properties

Question 14

what are the properties of graphite?

Answer 14

• each carbon atom is covalently bonded to 3 other carbon atoms
• layers of hexagonal rings with no covalent bonds between them
• layers can slide over each other, soft and slippery
• on electron from each carbon atom is delocalised
• can conduct electricity

Question 15

what is graphene?

Answer 15

a single layer of graphite

Question 16

what are fullerenes?

Answer 16

molecules of carbon atoms with hollow shapes, based on hexagonal rings of carbon atoms

Question 17

what are carbon nanotubes?

Answer 17

cylindrical fullerenes with very high length to diameter rations

Question 18

what can fullerenes be used for?

Answer 18

• lubricants
• to deliver drugs in the body
• catalysts

Question 19

what can nanotubes be used for?

Answer 19

reinforcing materials eg. tennis rackets

Question 20

milli, micro and nano?

Answer 20

• milli = (10^-3)
• micro = (10^-6)
• nano = (10^-9)

Question 21

how many nano meters across are nanoparticles?

Answer 21

1-1000 nanometers

Question 22

what are the uses of nano-silver?

Answer 22

it kills bacteria, so it’s used in wound dressings and deodorants

Question 23

what are the uses of nano-titanium dioxide?

Answer 23

so small that they don’t reflect visible light and cannot be seen, so it’s used in sunblocks because they block harmful ultraviolet light

Question 24

wha are the risks of nanoparticles?

Answer 24

• so small they could enter the bloodstream
• long-term effects aren’t known
• could enter and damage the environment

Question 25

what are smart materials?

Answer 25

materials that are responsive to certain stimuli [temperature, light and moisture]

Question 26

examples of smart materials:

Answer 26

• shape memory alloys/polymers -> can be bent and deformed but return to their original shape when heated
• thermochromic materials -> change colour when they reach a certain temperature
• photochromic pigments -> change colour when exposed to light
• polymer gels - >hydrogels absorb up yo 1000x their volume in water, changes in pH and temperature cause the water to be released

Question 27

shape memory alloy uses:

Answer 27

inside car bodies and plates for bone fractures

Question 28

shape memory polymer uses:

Answer 28

gum shields and medical stitches

Question 29

thermochromic material uses:

Answer 29

mugs that change colour when their contents are hot

Question 30

photochromic pigment uses:

Answer 30

sunglasses that darken when in bright sun

Question 31

polymer gel uses:

Answer 31

nappies, fake snow and hair gel