Topic 4 - States of matter

Question 1

State

Ideal gas equation

Answer 1

pV = nRT

p - pascal
v - m3
n - mol
R - 8.314 J /k mol
t - Kelvin

Question 2

Descibe

Gas pressure

Answer 2

gases exert pressure through collisions with the walls of a container

Question 3

Effect of temperature on pressure

at constant volume

Answer 3

temperature increase leads to increase in pressure as the particles gain KE, move faster an therefore collide more often with the walls

Question 4

Effect of volume on pressure

at a constant temperature

Answer 4

decrease in volume means the particles are squashed together and therefore they collide more frequently with the container walls and therefore pressure increases

Question 5

What are the assuptions of ideal gases?

Answer 5

• **No intermolecular forces of attraction or repulsion
• gas particles have zero volume**
• all collisions are elastic

Question 6

Limitations of the ideal gas law

Answer 6

At very high pressures and low temperatures
Molecules are close to each other
There are instantaneous dipole- induced dipole or permanent dipole- permanent dipole forces between the molecules
These attractive forces pull the molecules away from the container wall
The volume of the molecules is not negligible
At low temeperatures gases start to liquefy and intermolectular forces become more significant

Question 7

Diffrentiate between bonding and structure

Answer 7

bonding refers to the way atoms are held together whilst
structure refers to they way atoms are arranged relative to eachother

Question 8

Giant ionic Lattices

Answer 8

• High melting and boiling points due to strong electrostatic forces of attraction
• melting points increase with charge density due to greater attraction between ions
• soluble in water as ions can form ion-dipole bonds in which the energy released is greater than the energy required to break thebonds

Question 9

How does the type of basic particles a compund contains affect physical properties?

Answer 9

• To be soluble in water a compound must contain ions or polar molecules

Question 10

How does bonding affect physical properties

Answer 10

the stronger the bonds the higher the melting points and the harder the substance

Ensure you know exactly which bonds are being broken

Question 11

Describe

Simple molecular lattice

Answer 11

Weak intermolecular forces of attraction therefore lower boiling points
Iodine - cube with 5 molecules on each face
Buckminsterfullerene C60 - sp2 hybridisation, unhybridised p-orbital allows for electrical conductivity, connected hexagons
Ice - to melt it, the intermolecular forces are broken NOT the hydrogen bonds

Question 12

Describe

Giant molecular lattice

Answer 12

Graphite - stong covalent bonds creating layers with weak intermolecular forces between them, allowing them to slide over eachother which is why it is a lubricant
Diamond - tetraheldral, strong covalent bonds, hardest substance
Silicon (IV) Oxide SiO2 - tetraderal 1 silicon bonded to 4 oxygen

stong intramolecular forces

Question 13

Describe

Metal lattice

Answer 13

Strong electrostatic force of attraction between metal cations and delocalised sea of electron, they is why metals can conduct electricity and have high melting points

Question 14

Why are ionic compounds soluble in water?

Answer 14

They can form ion-dipole bonds and they energy released during this bond is more than the energy required to break the bonds between ions

Question 15

Relate melting/boiling points to charge density

Answer 15

the more the charge density the higher the boiling point due to the greater electrostatic attraction of charges