Chemical bonds and structure—>properties Flashcards
How do particles move in a solid
They vibrate
How do particles move in a liquid
They slide over each other in a changing/random arrangement
Why do some ionic solids dissolve in water
Water molecules can split up lattice
How are ions held together in ionic bonding
.Ionic bonds act in all directions + attract oppositely charged ions
.Giant structure/lattice formed
How do particles move in a gas and how does it cause pressure
- They move very quickly in all directions
2. They bash against walls of their container which exerts a force which causes pressure
What, in terms of particles, happens when a solid melts
- Particles vibrate faster as temp increases
- Enough energy transferred to solid for forces between particles to break
- Particles break away from fixed positions —> liquid
What, in terms of particles, happens when a liquid evaporates
- Particles move faster as temp increases
- Some particles escape from surface before boiling point reached
- Bubbles form in liquid + rise to surface
Why do ionic compounds have high melting/boiling points
.Large structures —>many electrostatic forces—>lots of energy required to overcome ionic bonds to melt solids
EVERY IONIC STRUCTURE IS SOLID AT ROOM TEMP
A) Why is the particle model limiting
B) How can particles vary
A) Assumes particles = solid spheres (which they are neither of) with no forces between B) -in size -can be atoms, molecules or ions -Some can contain many atoms
When will intermolecular forces give the molecule a higher melting point
When the molecule is larger because the force will be higher
What does ionic bonding effectively bond together
Oppositely charged ions
Why can ionic compounds only conduct when molten or dissolved
Ions are free to move so can carry charge
NO ELECTRONS
What is the limit of most models (3)
.Don’t show actual shape of molecule
.Electrons aren’t shown to be constantly moving
.Don’t show all electrons identically
What force separates neighbouring molecules and how does it affect the attraction between them
Intermolecular forces and they give simple molecules little attraction for each other
What is a polymer
A substance consisting of many small molecules covalently bonding to form long chains
Why are polymers solid at room temperature
They have strong intermolecular forces because they are large molecules
Where does metallic bonding occur
In metallic elements and alloys
What happens during metallic bonding
1) No electrons physically leave structure
2) electrons can move throughout metal making atoms into ions
3)
Why do metals have high melting and boiling points
Electrostatic forces between atoms and delocalised electrons
What is the empirical formula of 60g magnesium and 40g oxygen
60/24=2.5 moles
40/16=2.5 moles
1:1
MgO
How do you draw a repeating unit of poly(ethene)
/H H\
( C - C )
\H H/ n
n = large number
How are the electrons in an electronic structure able to move throughout it
The electrons in the outer shell of metal atoms are delocalised
Why do small molecules not conduct electricity
The molecules don’t have an overall charge
How are atoms arranged in metals
In layers
Why are alloys harder than pure metals
The bigger or smaller atoms from the other pure metal distorts the layers of the other pure metals
I
L __ greater force for layers to slide over each other
Why are metals good thermal conductors
Because energy is transferred by the delocalised electrons
