liquids, solids and intermolecular forces Flashcards
what is crystalline and amorphous solids
atoms or molecules that
compose them are arranged in a well-ordered three-dimensional array
atoms or molecules that compose them have no long range order
low density of gaseous water is due to
the distance between each molecules is very large
why is ice less dense than water
due to the unique crystal structure due to which the molecules move farther apart upon freezing
why is the water molecules in liquid water able to move
freedom of movement is there even though the atoms and molecules in liquid are in close contact but the thermal energy partially overcomes this attraction
why are protons and electrons attracted to each other
because when they come closer their potential energy decreases
the same goes for molecules with partial or temp charges
what is the reason behind the relative weakness of intermolecular forces wrto bonding forces
it is due to Coulomb law
Bonding forces are the result of large charges (the charges on protons and electrons) interacting at very close distances.
Intermolecular forces are the result of smaller charges interacting at greater distances.
which is the force present between all atoms and molecules and what causes it
dispersion force or London forces
it is caused by fluctuations in the electron distribution in atoms or molecules that is due to an instantaneous dipole or temporary dipole
on what does the magnitude of dispersion force depend on
it depends on how easily the electrons in an atom or molecule move or polarize in response to an instantaneous dipole which in turn depends on the size of the electron cloud
why does a large electron cloud result in larger dispersion force
the electrons are not held tightly by the nucleus hence the electrons can moves more freely
dispersion force increases with increase in molar mass
dipole-dipole force s caused by
exists between all polar molecules
polar molecules have electron-rich region(-vely charge) and electron deficit region as seen in acetone which has a permanent dipole
miscibility depends on
polarity of the compounds or molecules
why does polar molecules have higher bp amd mp than non polar molecules
this is due to the presence of dispersion forces with the dipole-dipole forces this additional attractive forces rises mp and bp
what is miscibility
the ability to mix without separating into 2 states – of liquids
bp increases with
increase in dipole moment
what is the electronegativity of carbon oxygen and hydrogen? and chlorine
c-2.5
o-3.5
H-2.1
Cl-3
why is co2 molecule non polar
their structure is linear hence dipoles of polar bonds cancel each other out hence no dipole-dipole forces
hydrogen(super dipole-dipole force) bond is seen in
polar molecules containing hydrogen bonded directly with smaller electronegative atoms like fluorine, nitrogen, or oxygen these show hydrogen bonding
a hydrogen bond is caused by
The large electronegativity
difference between hydrogen and any of these electronegative elements causes the hydrogen atom to have a fairly large partial positive charge (d+) within the bond, while the F, O, or N atom has a fairly large partial negative charge (d-). In addition, since these atoms are all quite small, the H atom on one molecule can approach the F, O, or N atom on an adjacent molecule very closely. The result is a strong attraction between the H atom on one molecule and the F, O, or N on its neighbor—an attraction called a hydrogen bond
state of ethanol and dimethyl ether in room temp
ethanol-liquid
dimethyl ether-gas
what is ion-dipole force
occurs when an ionic compound is mixed with a polar compound
eg aqueous soln of ionic compounds
what is surface tension
The surface tension of a liquid is the
energy required to increase the surface area by a unit amount. For example, at room temperature, water has a surface tension of 72.8 mJ>m2; it takes 72.8 mJ to increase the surface area of water by one square meter
surface tension decreases with
decrease in intermolecular forces
paper clip cannot float on benzene bcs it only has dispersion forces
what is viscosity
it is the ability of a liquid to resist flow
what are the factors affecting viscosity
1-intermolecular forces stronger the force more viscous the liquid
2-size and shape of molecules large molecules cant move easily hence resist flow
3-temperature - ke increases less viscosity
KE decreases viscosity increases
what is cohesive force
intermolecular force between molecules of a liquid
what is adhesive force
interaction between molecules of a liquid and solid surface
ability of liquid to adhere to the surface
why does liquid form spherical shape when it comes in contact with non polar surface
bcs cohesive force>adhesive force
and spherical droplets maximise hydrogen bonding
what is the full form of SAE
society of Automotive engineers
The thinnest motor oils have SAE ratings
of 5 or 10, whereas the thickest have SAE ratings of up to 50
what is capillary action
the ability of a liquid to flow
against gravity up a narrow tube
give the reason for concave meniscus in water and convex meniscus in mercury
concave meniscus-adhesive force>cohesive force
convex meniscus-adhesive force<cohesive force- due to metallic bonding between atoms
what is vaporization
the process by which thermal
energy can overcome intermolecular forces and produce a state change from liquid to
gas
what are volatile and non-volatile and give an example for each
volatile are compounds that vaporize very easily eg-acetone
non-volatile are substances that does not vaporize very easily eg-motor oil 10w-40
Summarizing the Process of Vaporization:
■ The rate of vaporization increases with increasing temperature.
■ The rate of vaporization increases with increasing surface area.
■ The rate of vaporization increases with decreasing strength of intermolecular forces.
condensation is a
exothermic process
vaporization is a
endothermic process
vaporization requires overcoming the intermolecular forces that hold liquids together. Since
energy is needed to pull the molecules away from one another, the process is endothermic
what is the enthalpy of vaporization (𝚫Hvap).
The amount of heat required to vaporize one mole of a liquid to gas
H2O(l) + H2O(g) ∆Hvap = +40.7 kJ>mol
The heat of vaporization is always positive because the process is endothermic
dynamic equilibrium
rate of vaporization=rate of condensation
what is the vapor pressure? and what does it depend on
The pressure of a gas in dynamic equilibrium with its liquid
intermolecular forces present
in the liquid and the temperature
give example for a balanced system
A liquid in dynamic equilibrium with its vapor is a balanced system that tends to
return to equilibrium if disturbed
what is the vapor pressure of n-pentane at 25 degree celsius
510mmhg
state le chateliers principle
When a system in dynamic equilibrium is disturbed, the system
responds so as to minimize the disturbance and return to a state of
equilibrium.
temperature dependence of vapor pressure
When the temperature of liquid increases, its vapor pressure rises because the higher thermal energy increases the number of molecules that have enough energy to vaporize
what is boiling point
it is the temperature at which the vapor pressure of a liquid is equal to the external pressure
When a liquid reaches its boiling point, the thermal energy is enough for molecules in the interior of the liquid (not just those at the surface) to break free of their neighbors and enter the gas state
what is normal boiling point
the temperature at which its vapor pressure equals 1 atm
what is critical temperature
it is the temperature at which the meniscus between the liquid and gaseous
n-pentane disappears, and the gas and liquid states commingle to form a supercritical fluid
it is the temp at which this transition occurs
the liquid cannot exist above this temp
what is critical pressure
it is the pressure at which the transition occurs
what is supercritical fluid
it is neither gas nor liquid but it exhibits both of its properties
it acts as a good solvent
used to extract caffeine from coffee beans without losing its flavour using supercritical carbondioxide
WHAT is sublimation and how does it occur
Even though a block of ice is solid, the water molecules in the ice have thermal energy,
which causes each one to vibrate about a fixed point The molecules with high enough thermal energy can break free from the ice
surface and go directly into the gas state
what is deposition
Some of the water molecules in the gas state (those at the low end of the energy distribution curve for the gaseous molecules) collide with the surface of the ice and are captured by the intermolecular forces with other molecules. This process—the opposite of sublimation—is deposition
name a substance that does not melt but only sublimes
dry ice or solid carbondioxide
what is melting or fusion
The increasing thermal energy causes
the water molecules to vibrate faster and faster. At the melting point (0 °C
for water), the molecules have enough thermal energy to overcome the
intermolecular forces that hold the molecules at their stationary points,
and the solid turns into a liquid
melting is
endothermic process
the melting ice absorbs
heat from the liquid
what is heat of fusion(𝚫Hfus)
it is the energy required to melt 1 mol of a solid
H2O(s) ¡ H2O(l) ∆Hfus = 6.02 kJ>mol
freezing is
exothermic process
what is enthalpy of sublimation
it is the energy required to sublime 1 mole of solid into gas
what does y axis and x axis represent in heating curve
y axis - temp of water sample
x axis- amount of heat added
what does regions in a phase diagram represent
Each of the three main regions—solid, liquid, and gas—in the phase diagram represents conditions
under which that particular state is stable
what does x axis and y axis represent in a phase diagram
x axis-temperature
y axis-pressure in torr
what does lines in a phase diagram represent
Each of the lines (or curves) in the phase diagram represents a set of temperatures and pressures at which the substance is in equilibrium between the two states on either side of the line
what does triple point in a phase diagram represent
The triple point in a phase diagram represents the unique set of conditions at which the three states are equally stable and in equilibrium. In the phase diagram for water, the triple point occurs at 0.0098 °C and 4.58 torr.
what doe critical point in a phase diagram represent
the critical temperature and pressure, the liquid and gas states coalesce into a supercritical fluid. The critical point in a phase diagram represents the temperature and pressure above which a supercritical fluid exists
Carbon dioxide forms a liquid only
above pressure of 5.1 atm
