states of matter Flashcards
What kinetic assumptions are made
when dealing with an ideal gas?
- The gas contains a large number of molecules moving in random
directions at random speeds. - Electrostatic forces between molecules is negligible, except during
collisions. - Collisions are perfectly elastic.
- Time of collisions between molecules is negligible compared to time
between collisions. - The molecules of a gas occupy negligible volume compared to the total
volume of the gas.
What kinetic assumptions are made
when dealing with an ideal gas?
- The gas contains a large number of molecules moving in random
directions at random speeds. - Electrostatic forces between molecules is negligible, except during
collisions. - Collisions are perfectly elastic.
- Time of collisions between molecules is negligible compared to time
between collisions. - The molecules of a gas occupy negligible volume compared to the total
volume of the gas.
What are the conditions necessary for a gas to
approach ideal behaviour?
● Low pressure
● High temperature
What are the limitations of an ideal gas
at very low temperatures and very high pressures?
● Intermolecular forces are no longer
negligible and have to be considered.
● Molecular size is also no longer
negligible and has to be considered.
What is the ideal gas equation?
pV = nRT p - pressure (Pa) V - volume (m3) n - number of moles (mol) R - gas constant (8.314 J K-1 mol-1) T - temperature (K)
The ideal gas equation can be used with
which other equation to find molecular
mass?
M = m/n
M - molecular mass
n - number of moles (mol)
m - mass (g)
Use the kinetic-molecular model to describe the
liquid state
● Particles are close together but not regularly arranged. ● Particles have a little more kinetic energy than in a solid. ● There are fewer electrostatic forces between particles than in a solid, allowing particles to move past each other and flow.
In terms of the kinetic-molecular model,
what happens during melting?
● Solid → Liquid
● Increasing the temperature of the surroundings
causes particles to absorb energy meaning they gain
more kinetic energy.
● Eventually, the particles gain enough energy to
disrupt the regular arrangement and become a liquid.
How do particles act during vaporisation?
● Liquid → Gas
● Heat energy causes particles in a liquid to
move fast enough to break all forces of
attraction between them and become a gas.
What is vapour pressure?
When a liquid evaporates in a closed
container, the gaseous particles move around
above the liquid. When these particles collide
with the walls of the container, they exert a
pressure called the vapour pressure.
Describe the structure of a solid ionic compound
● Regular, repeating arrangement (lattice). ● Caused by the electrostatic attraction between the oppositely charged ions.
Describe the lattice structure of iodine
● Iodine is an example of a simple
molecular lattice.
● Iodine, I2 molecules form a larger structure due to intermolecular forces (Van der Waals Forces) between molecules. ● The structure is described as face centred cubic.
What is an allotrope?
Allotropes are different physical forms of
an element in the same state.
Describe the structure of a fullerene
Lattice structure
E.g. a buckminsterfullerene
(C60) is a molecule consisting of 60 carbon atoms arranged
in pentagons and hexagons.
What is a nanotube?
A graphene sheet rolled up
into a tube (single sheet of
carbon atoms covalently
bonded together)
Describe the structure of diamond
● Giant covalent lattice.
● Each carbon atom is covalently bonded to four
other carbon atoms.
● Extremely strong structure.
● Bond shape and angle around each carbon:
Tetrahedral, 109.5°.
Describe the structure of graphite
● Giant covalent lattice. ● Made from layers of carbon arranged in hexagonal rings. ● There are weak london forces between layers. ● Each carbon atom bonds covalently to 3 other carbon atoms. ● One delocalised electron per carbon.
Describe the structure of graphene
● Giant covalent lattice. ● Single layer of graphite. ● Each carbon atom is bonded to 3 other carbon atoms to create a hexagonal ringed structure. ● One delocalised electron per carbon.
Describe the structure of silicon(IV) oxide
Describe the structure of silicon(IV) oxide
● Similar 3D structure to diamond.
● Silicon and oxygen atoms covalently
bonded together.
Describe the structure of ice
Describe the structure of ice
● Open lattice structure.
● Hydrogen bonds hold water
molecules apart in hexagonal rings.
Describe the structure of a metal
(e.g. copper)
Giant metallic lattice with positive ions packed
closely together with delocalised electrons.
In copper, each atom is surrounded by 12
other copper atoms.
What does a diagram of metallic bonding look like?
● Positive charges =
ions
● Negative charges =
electrons
What is a finite resource?
A resource that is used up faster than it
is replaced. This resource will run out if it
is continually used.
Why is recycling important?
● To conserve finite resources for as long as possible
by reducing the rate at which the are used.
● Reduces greenhouse gas emissions (which cause
global warming).
● May reduce costs and other environmental impacts
of a material.
How does hydrogen bonding affect the
boiling and melting points of a
substance?
Hydrogen bonding is the strongest type of
intermolecular bond and hence requires a lot of
energy to overcome when boiling/ melting a
substance. As a result, structures that contain
hydrogen bonding often have higher melting and
boiling points than expected.
How does hydrogen bonding affect the viscosity of a
substance?
Hydrogen bonds increase viscosity of a
substance because these bonds (as well
as any other intermolecular forces) make
the substance more resistant to flow.
How does hydrogen bonding create
surface tension in water?
Hydrogen bonding increases surface tension.
Water molecules at the surface of the liquid are
attracted more strongly to other water molecules
around them than the layers of water molecules
below, creating tension at the surface of the liquid.
What does boiling point suggest about structure and
bonding?
A high boiling point indicates a giant
structure (ionic metallic or giant covalent).
A low boiling point indicates simple
molecules (or atoms for noble gases).
What does solubility suggest about structure and
bonding?
Compounds that are soluble in water tend to be
ionic.
If a soluble compound has a low boiling point, it
may be small and very polar or able to form
hydrogen bonds.
What does electrical conductivity suggest about
structure and bonding?
If a solid substance conducts electricity, it is
likely to be a metal, graphene or graphite.
If a substance only conducts when molten or
dissolved, it is an ionic compound.
What do appearance/ malleability suggest about
structure and bonding?
If a substance is brittle, it is likely to be
ionic or giant covalent.
If a substance is shiny, malleable and
ductile, it is likely to be a metal.
