states of matter Flashcards
(31 cards)
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.
