TOPIC 2 - Bonding, Structure, Properties of Matter

What happens to Calcium + Chlorine atoms when they form calcium chloride?:

• Each calcium atom loses two electrons

• Each chloride atom gains one electron

• So 1 Calcium reacts with 2 Chlorine atoms

• To form Ca2+ and Cl- ions

• The oppositely ions attract to form a compound

Why can't ionic compounds be electrolysed as solids?

the ions can't move

Why is methane a gas at room temperature?:

methane is a small molecule; so weak intermolecular forces; require little energy to overcome; the boiling point is very low

How do metals conduct thermal energy?:

thermal energy is transferred; by delocalised electrons

How do metals conduct electricity?:

metals have delocalised electrons; they carry electrical charge; and move throughout the structure

Why might alloy not conduct electricity as well as pure metals?:

the different sized atoms distort the layers of the structure; so the movement of the delocalised electrons is restricted

Describe the structure and bonding of diamond:

• giant structure

• covalent bonds

• four bonds per carbon atom

Why does diamond have a very high boiling point?

the covalent bonds are very strong; so a lot of energy is required; to break the bonds

What is the shape of a Buckministerfullerene molecule?:

spherical

Uses of fullerenes:

• drug delievery around the body

• hydrogen storage

• anti-oxidants

• reduction of bacterial growth

• catalysts

• cylindrical fullerenes for strengthening materials

• spherical fullerenes for lubricants (roll over each other)

Why are fullerenes suitables for delievering medicine around the body?

They are hollow so can cage the drug; unreactive; not toxic; large SA:V

Why is graphite a good electrical conductor + soft, slippery?:

• bonds are covalent

• giant structure

• three covalent bonds per carbon atom (3 electron used)

• so 1 electron per carbon atom is delocalised

• these electrons can move through the structures and carry electrical charge -> conducts electricity

• the layered structure of interlocking hexagonal rings

• with weak intermolecular forces between layers/ no covalent bonds between them

• so layer can easily slide over each other

Why are alloys stronger than pure metals:

alloys have different sized atoms; so the layers are distorted; layers can't easily slide over each other

What is the volume of 1 mole of gas at room temp?:

24dm^3

Why are nanoparticles better than fine particles?:

• they have a higher SA:V

• less material is needed for the same effect

• (for windows: more light gets through)

Compare structure + bonding of CO2, MgO, SiO2:

• CO2 + SiO2 are made of atoms; MgO of ions

• SiO2 + MgO are giant structures; CO2 small molecules with weak intermolecular forces

• all 3 compounds have strong bonds

• CO2 and SiO2 are formed from 2 non-metals; bonds are covalent (electrons are shared)

• MgO is formed from metal and non-metal; so bonds are ionic (electrons are transferred from Mg to O)

• bonds in SiO2 are single bonds - each Si forms 4 bonds, each O 2 bonds

• CO2 - double bonds (C 2 double bonds, O 1 double bond)

Why is it important to use a reaction with a high atom economy?:

more sustainable; less waste

A ball and stick model is not an accurate representation of ionic compounds because…?:

there are no gaps/ sticks between the ions

What is the relative formula mass (Mr), in grams, the same as?:

one mole of the substance

Describe a method to compare metal reactivities with zinc, and silver nitrate?:

measure the temperature change; when add each metal to the silver nitrate solution; of the same con/vol; use same mass/moles of metal; the greater the change, the more reactive

What is glass made from?:

limestone; sodium carbonate; sand

Why is a stronger material good?

less easily damaged

Why is a lower density material good?:

lighter to install

Why is cryolite added to Aluminium oxide?:

Because the mixture has a lower boiling point; less energy needed to melt (less expensive)

What is bronze an alloy of?:

Copper + Tin

What are the uses of brass?:

ornaments; musical instruments; hinges/knobs/screws

Why are alloys better than pure metals?:

harder; (can be cheaper)

How is stainless steel better than steel?:

does not corrode; does not react with water; is hard

Which type of steel is best for shaping?

(low carbon steel, high carbon s, stainless st): low carbon steel

What is brass an alloy of?:

copper + zinc

What gets discharged at each electrode in electrolysed?:

anode - halide ions/ oxygen; cathode - less reactive metal than hydrogen/ hydrogen

What is the name for alloys that return to their original shape once heated?:

shape memory alloys

What is the metallic structure?:

a giant, regular structure of positive metal ions in layers, held together by a 'sea' of delocalised electrons