Intermolecular Forces+condensed Matter Flashcards
What are intramolecular forces
They keep together the atoms within the molecules and ionic compounds(bonds)
What are intermolecular forces
Interactions that occur between the molecules. They are responsible for formation of liquid and solid and state in ehich substance exist at a particular temperature and pressure
How are condensed phases held together
By attractive interactions between the molecules
Are intermolecular forces stronger than covalent bonds
No
Types of intramolecular forces
•ion-ion interactions
(These 2 are van der waals interactions)
•Dipole-dipole int.
•dispersion forces(London)-(instant)dipole-induced dipole
—–
•hydrogen bond->dipole-dipole
Explain polarity in diatomic molecule
If 2 elements are of the same electronegativity that compound in non-polar. When two elements have different electronegativity, the dipole is created where one side of the molecule is negatively charged(б-) and other positively(б+). Direction of molecular dipole is represented by the arrow that goes from б- to б+
What is polar molecule
Any molecule with non-zero dipole moment. The units of dipole moment are debyes, D
Explain polarity in polyatomic molecules
The dipole moments can cances each other out(ex. б- ,б+,б-) because direction of the dipole is in the center and they cancel each other. While б+,б-,б+ doesnt cancel each other because it goes into different directions
What does determine that polyatomic molecule is polar or not
It’s shape and whether the polarities of individual bonds cancel out
What kind of interactions do molecules with the dipole moment have
Electrostatic
How do molevules in liquids align
They want to maximize attraction forces
What kind of attractive interactions exist in non-polar substances
Dispersion/London forces
Explain how temporary dipole is created
When a molecule with a dipole approaches molecule without one, it induces movement of e- causing temporary dipole
What is measured by polarizability
The strength of induced dipole. It also explains how easily it is to move electron cloud of non polar molecule around
What increases intersction between instantenuous dipoles
Molar mass(more e-) and shape(higher in long and non symmetric molecules)
Explain hydrogen bond
H attracted to O,N,F is attracted to electronegative atom od adjacent molecule
What causes boiling point to be higher
Van der waals forces(higher they are(higher molecular mass is)higher the boiling point. Exception are liquids that form hydrogen bonds, their boiling points are higher than excepted taking into accaunt molecular mass
What is stronger, Van der Waals or hydrogen bonds
Hydrogen
Can carbon form hydrogen bonds
No
What attractions are broken when the phase changes happen
Intermolecular
What do we take into accaunt when classifying solids
Bonds
Classify solids
•ionic solids- electrostatic interaction between oppositely charged ions hold it together. They have high melting and boiling points. They conduct electricity in the solution and in the liquid phase
•molecular solids-they are kept together through intermolecular forces. Low melting and boiling points. They are poor electrical conductors
•metals-cations kept together through cloud of delocalized e-. Wide range of melting points,conduct electricity and heat
•covalent netword solid-infinite structures where non-metal elements are linked through covalent bonds. High melting and bpiling points
Explain formation of metal solids
Metals have low ionization enthlapies so they lose their valence e-. The free electron model considers the lattice as being made up of metal ions, surrounded by a sea of delocalized e-.
Explain how metals conduct electricity
Normally, e- move into random direction but then potential difference is applied, e- move from high to low potential which gives rise to a current. Thats why they conduct electrcity
What does malleable and ductile mean
Malleable- hammered into sheets
Ductile- drawn into wires
Ehy are metals malleable and ductile
Planes of metal can slip past one another when force is applied
Formula for density
р=m/V. [g/cm³]
What properties in a liquid do intermolecular forces determine
•surface tension
•viscosity
•vapour pressure
What is viscosity
Resistance of a fluid to flow. The stronger the intermolecular forces–> higher viscosity. It decreases with temperature
Explain surface tension in a liquid
Liquids tend to take the lowest surface tension as possible. It results from the greater attraction between liquid molecules than with molecules in the air.
Explain vapoud pressure
It’s the pressure of vapoud when liquid is boiled. If we close the container, vapoud and liquid come to equilibrium and then vp is called the saturated vp
What are volatile solids and liquids
They have high vapour pressure
Is solid form of water more or less dense than the liquid one
Less
