3.7- BONDING AND PHYSICAL PROPERTIES Flashcards
What is matter?
anything with mass
What is matter made of?
tiny particles- it is particulate
As the particles in matter are in motion, what do they have?
kinetic energy
What is the arrangement of particles in solids?
regular
What is the arrangement of particles in liquids?
random
What is the arrangement of particles in gases?
random
What is the evidence for solids having a regular arrangement of particles?
crystal shape have straight edges
solids have definite shapes
What is the evidence for liquids having a random arrangement of particles
none direct but a liquid changes shape to fill bottom of its container
What is the evidence for gases having a random arrangement of particles
none direct but a gas will fill its container
What is the spacing like in solids?
close
What is the spacing like in liquids?
close
What is the spacing like in gases?
far apart
What is the evidence for close spacing in solids?
solids are not easily compressed
What is the evidence for close spacing in liquids?
liquids are not easily compressed
What is the evidence for far apart spacing in gases?
gases are easily compressed
What is the movement of particles of solids like?
vibrating about a point
What is the movement of particles of liquids like?
rapid ‘jostling’
What is the movement of particles of gases like?
rapid
What is the evidence for the movement of particles in solids vibrating about a point?
diffusion is very slow
solids expand on heating
What is the evidence for the movement of particles in liquids rapidly ‘jostling’?
diffusion is slow
liquid evaporates
What is the evidence for the movement of particles in gases being rapid?
diffusion is rapid
gases exert pressure
What happens when you first heat a solid and supply energy to the particles?
makes them vibrate more about a fixed position
What does heating a solid and supplying energy tot he particles slightly increase?
slightly increases average distance between particles and so solid expands
What do you do turn a solid into liquid?
supply more energy to it than just heating the solid
Why is more energy needed when turning a solid into a liquid?
to weaken forces that act between particles , holding them together in solid state
What is the energy needed to turn a solid into liquid called?
enthalpy change of melting
What does not change while a solid is melting?
temperature
Why does the temperature not change while the solid is melting?
heat energy provided is absorbed as forces between particles weakened
What is the enthalpy?
heat energy change measured under constant pressure whilst temperature depends on average K.E. of particles and so is related to their speed- greater the energy, faster they go
when you heat a liquid what happens to the particles?
supply energy to particles which makes them move more quickly-more K.E.
What happens to the spacing in liquids when it’s heated?
on average, particles move a little further apart so liquids also expand on heating
What must you do to turn a liquid into a gas?
supply enough energy to break all intermolecular forces between particles
What does a gas consist of?
particles that are far apart + moving independently
What is the energy needed to turn a liquid into gas called?
enthalpy change of vaporisation
Is there temperature change when a liquid turns to gas?
no
What do the particles gain when you heat a gas and what do they do?
gain K.E. and move faster
What happens to the spacing in gases when they’re heated?
get much further apart and so gases expand a great deal on heating
What state of matter are crystals?
solids
What arrangement do the particles have in crystals?
regular arrangement
What are the particles in a crystal held together by?
forces of attraction
What could the forces of attraction between the particles in a crystal be?
strong bonds- covalent, metallic or ionic
or weak intermolecular forces- van der Waals, dipole-dipole, or hydrogen bonds
What does the strength of the forces of attraction between the particles in a crystal affect?
physical properties of crystals
What happens to the melting temperature and enthalpy of fusion, the stronger the force between particles in a crystal?
higher melting temp and greater enthalpy of fusion
What are the 4 basic crystal types?
ionic, metallic, molecular and macromolecular
What do ionic compounds have between the oppositely charged ions?
strong electrostatic attractions
Example of a typical ionic crystal?
sodium chloride, NaCl
What is the melting point of ionic compounds like?
high melting points
Why do ionic compounds have high melting points?
because of strong electrostatic attractions that extend throughout structure
these require a lot of energy to break for ions to move apart from one another
What do metals exist as? (hint-lattice)
lattice of positive ions embedded in a delocalised sea of electrons
What attraction is there throughout the metal crystals?
attraction of positive to negative extends throughout the crystal
What is the high melting temperature in metals due to?
strong metallic bonds
What do molecular crystals consist of?
molecules held in a regular array by intermolecular force
What do the covalent bonds in molecular crystals hold together?
covalent bonds WITHIN molecule hold atoms together
Where do covalent bonds not act in a molecular crystal?
do not act BETWEEN molecules
What is the melting temperatures of molecular crystals like?
low melting temperatures
What is the enthalpies of melting like for molecular crystals?
low enthalpies of melting
Why do molecular crystals have low melting temperatures and low enthalpies of melting?
intermolecular forces much weaker than covalent, ionic or metallic bonds
What is an example of a molecular crystal?
iodine
What holds pairs of iodine atoms together to form I2 molecules? (molecular crystals)
strong covalent bonds
Do iodine molecules have a large number of electrons?
yes
What does iodine molecules having a large number of electrons cause?
van der Waals forces strong enough to hold molecules together as solid
As van der Waals forces are much weaker than covalent bonds, what properties does it give iodine? (3)
crystals soft + break easily
low melting temp + sublimes readily to form gaseous iodine molecules
doesn’t conduct electricity as there are no charged particles to carry charge
Are covalent compounds always made up of small molecules?
no
In some substances where do the covalent bonds extend? (macromolecular crystals?
extend throughout compound
What typical property of a giant structure held together with strong bonds do substances with covalent bonds extending throughout the compound have? (macromolecular crystals)
high melting temperature
Examples of macromolecular crystals? (2)
diamond and graphite
What are diamond and graphite made up of?
carbon only
What are diamond and graphite called in association with carbon?
polymorphs and allotropes of carbon
Why are diamond and graphite very different materials?
their atom are differently bonded + arranged
What does diamond consist of?
pure carbon with covalent bonding between every carbon atom
Why is diamond a giant structure?
bonds spread throughout the structure
How many electrons does a carbon have in its outer shell?
four electrons
How many single covalent bonds does each carbon atom form in diamond?
forms 4 single covalent bonds with other carbon atoms
What do the four electrons pairs of each carbon in diamond do?
repel each other, following rules of electron pair repulsion theory
Where do the bonds point in three dimensions? (diamond)
point to corners of a tetrahedron (bond angles of 109.5°
What is the positions of the carbon atoms like in diamond?
each carbon atom is in an identical position in the structure, surrounded by 4 other carbon atoms
What do the carbon atoms in diamond form?
giant three-dimensional lattice of strong covalent bonds
What properties does diamond have? (3)
very hard material (one of the hardest known)
very high melting temp, over 3700K
doesn’t conduct electricity as there are no free charged particles to carry charge
What does graphite consist of?
pure carbon but atoms bonded + arranged differently from diamond
How many sorts of bonding does graphite have?
2
What are the 2 sorts of bonding that graphite have?
strong covalent
weaker van der Waals forces
How many single covalent bonds does each carbon atom form in graphite?
3 single covalent bonds
What is the shape of the graphite molecule and what bond angles?
flat trigonal arrangement, sometimes called trigonal planar, with bond angle of 120°
What does each carbon atom forming 3 single covalent bonds in graphite leave?
leaves each carbon atom with a ‘spare ‘ electron in a p-orbital that’s not part of the 3 single covalent bonds
What does the flat trigonal arrangement/ trigonal planar in graphite produce?
two-dimensional layer of linked hexagons of carbon atoms
What do the p-orbital of the carbon atoms in the graphite with the ‘spare’ electron do?
merge above and below the plane of the carbon atoms in each layer
When the p-orbitals merge above and below of the plane of the carbon atoms in each layer, what can the electrons do? (graphite)
electrons can move anywhere within the layer- delocalised
What does the delocalised electrons from the p-orbitals merging add on to? (graphite)
adds to strength of bonding
What does the delocalised electrons allow graphite to do?
conduct electricity
What can the delocalised electrons do? (graphite)
travel freely through material
Which plane does graphite conduct along and which one does it not ?
only conduct along hexagonal planes, not at right angles to them
Are there covalent bonds between the layers of the carbon atoms in graphite?
no
How are the layers of carbon atoms in graphite held together?
weaker van der Waals forces
What does the weak intermolecular force of attraction (VDW) between the carbon layers in graphite mean?
layers can slide across one another
What does the layers of carbon being able to slide across one another make graphite?
makes graphite soft and flaky
What is graphite used in?
lead in pencils
What does graphite being flaky allow? (in reference to pencil)
allows graphite layers to transfer from pencil to paper
Properties of graphite (3)
soft material
very high melting temp + in fact breaks down before it melts- because of strong network of covalent bonds, which make it a giant structure
conducts electricity along planes of hexagons
When was the first other form of pure carbon discovered?
when chemists were looking for molecules in outer space
What do new forms of pure carbon structures include? (2)
closed cages of carbon atoms
tubes called nanotubes
What is the most famous other form of pure carbon?
buckminsterfullerene, C60
How are atoms arranged in buckminsterfullerene?
arranged in football-like shape
What property best tells us what sort of bonding you have?
electrical conductivity
What conducts electricity well? (2)
metals and alloys
What are alloys?
mixture of metals
Do metals and alloys conduct electricity well in a solid and liquid state?
yes
Why do metals and alloys conduct electricity well in a solid and liquid state?
due to their metallic bonding
How is current carried in metals and alloys?
current carried by delocalised electrons that hold metal ions together
When do ionic compounds conduct electricity?
in liquid state (or when dissolved in water)
When don’t ionic compounds conduct electricity?
when they’re solid
How is current carried in ionic compounds?
by movement of ions towards electrode of opposite charge
What are the ions able to do when the ionic compound is liquid or dissolved in water?
ions free to move
What happens to the ions when ionic compounds are in solid states?
fixed rigidly in position
Generally do covalent bonded substances conduct electricity?
do not conduct electricity in either solid or liquid state
Why do covalent bonded substances generally not conduct electricity in solid or liquid states?
no charged particles to carry current
Are covalent compounds soluble in water?
often insoluble in water
What happens when covalently bonded substances do react with water?
react to form ions, i.e. ethanoic acid
What can the solution do when covalently bonded substances are dissolved in water?
can then conduct electricity
What does structure describe?
arrangement in which atoms, ions or molecules are held together in space
What is the property that best tells us if a structure is giant or simple molecular?
melting (or boiling) point
What is the melting (and boiling) points of simple molecular compounds like?
low melting (and boiling) points
What is the melting (and boiling) points of giant structures generally like?
high melting (and boiling) points
How are all molecular compounds bonded?
covalently bonded
What sort of bonding must all compounds with low melting (and boiling) points have?
covalent bonding
What structure can a compound with covalent bonding have?
either a giant structure or simple molecular structure
As a compound with covalent bonding can either be a giant structure or simple molecular structure, what can the melting (and boiling) point be like?
may have either a high or low melting (and boiling) point
What do you do when you heat melt + boil simple molecular compounds?
breaking intermolecular forces between molecules, not covalent bonds within them
What determines the melting (and boiling) points of simple molecular compounds?
strength of intermolecular forces
What are the 3 types of intermolecular forces in order of increasing strength?
van der Waals
dipole-dipole forces
hydrogen bonds
Where do van der Waals forces act?
between all atoms
Where do dipole-dipole forces act?
between molecules with permanent dipoles
Where do hydrogen bonds act?
between molecules formed when highly electronegative atoms (oxygen, nitrogen and fluorine) + hydrogen atoms are covalently bonded
