Liquids and Solids Flashcards
What is a solid in term of state of matter
A solid has a well-defined size and shape
What is a liquid in term of state of matter
A liquid takes the shape of the container in which it is placed
What is a gas in term of state of matter
A gas is another fluid form which can be easily compressed
What is a phase diagram
A diagram showing the way in which the state of a material depends on temperature and pressure
What are the 3 types of van der Waals forces
- London forces 2. Dipole-Dipole forces 3. Hydrogen bonding
What are London forces
These forces arise from the attraction between two instantaneous dipoles. The dipoles arise from fluctuations in the electron distribution model.
Which molecules are affected by London forces
All molecules are drawn together by London forces
What effect does molar mass have on London forces
The strength of London forces increases with molar mass since heavier molecules have more electrons
What effect does molecular shape have on London forces
Rod shaped molecules can get closer together than spherical molecules meaning that London forces are stronger
Which molecules are affected by dipole-dipole forces
Polar molecules (molecules with permanent partial charges) are affected by dipole-dipole forces
What are dipole-dipole forces
Polar molecules are drawn together by dipole-dipole forces
What molecules form hydrogen bonds
Hydrogen atoms and strongly electronegative atoms e.g. oxygen and fluorine
What are hydrogen bonds
When a hydrogen atom lies between two small, strongly electronegative atoms with a lone pair of electrons
How does water solidify
By hydrogen bonds
Describe the surface tension of water molecules
- The surface of a liquid is smooth because intermolecular forces pull the molecules together and inwards 2. There is a net pull inwards 3. Surface tension of water is much higher than most other liquids
What is capillary action
The attraction between water and other material such as glass accounts for capillary action
What does capillary action cause
The liquid rises because there are stronger forces between the water and the molecules in the surface of the capillary which results in a meniscus
What is viscosity
The viscosity of a liquid is its resistance to flow
What affect do intermolecular forces have on viscosity
Greater intermolecular forces result in higher viscosity, so the strong intermolecular forces reduce the ability of the liquid to flow
What is evaporation in relation to vapour pressure
Molecules leave the surface of an enclosed liquid continually
What is condensation in relation to vapour pressure
Molecules whilst evaporating can collide and come trapped again by the surface
Describe the dynamic equilibrium between evaporation and condensation
Evaporation and condensation are temperature sensitive- at higher temperatures more molecules leave the surface
What happens before saturated vapour pressure is reached
There is an increasing number of molecules in the vapour
What happens after standard vapour pressure is reached
There is a constant number of molecules in the vapour
How is boiling point defined
The temperature at which a liquid boils when atmospheric pressure is 1 atm
What is boiling point
When the vapour pressure of a liquid matches atmospheric pressure, the liquid vaporises so quickly that bubbles form
How do IMF affect boiling point
Strong intermolecular forces lead to high boiling points
What temperature does water boil at the top of Mount Everest
71°C
What is Raoult’s Law
The vapour pressure of a solvent in the presence of a non-volatile solute is proportional to the mole fraction of the solvent
How is Raoult’s Law mathematically expressed
P = (xsolvent) x (Ppure)
xsolvent = Nsolvent / (Nsolvent + Nsolute)
Where Nsolvent and Nsolute are the number of moles
Units of pressure are important in Raoult’s Law are important- true/ false
False, units of pressure don’t matter
What does the following graph show
A non-ideal solution
Which molecule has a higher boiling point
o-Dichlorobenzene
Which molecule has a higher boiling point
cis-Dichloroethene
Which molecule has a higher boiling point
1,1-Dichloroethene
