Transcript Splatter Test Lab

Splatter Test Lab
An introduction to intermolecular
forces
INTER vs INTRA
Forces
Intermolecular
Forces
Hydrogen
Bonding
Dipole-Dipole
Intramolecular
Forces
London
Dispersion
Forces
Covalent
INTRAMOLECULAR forces are stronger than INTERMOLECULAR forces.
Ionic
INTERMOLECULAR forces
Hydrogen Bonding
• Force of Attraction between a Hydrogen atom of one molecule and an N, O,
or F of another of the same molecule. VERY STRONG!! Found in Water!
Dipole• Found in polar molecules because of the DIPOLE (uneven distribution of
charge >0.4 electronegativity difference). Polar molecules dissolve other
polar molecules. Strong!
London Dispersion Forces
• Found in non polar and polar substances alike. This is an instantaneous
DIPOLE that occurs because atoms are moving around. VERY WEAK!!!
STRONGEST > WEAKEST: Hydrogen bonding> Dipole> London dispersion forces.
Examples of Each Type
Hydrogen Bonding
• Examples: Water, H2O, NH3, HF, H2O2, alcohols (H of one
compound and O,N,F of another)
Dipole• Examples: CH3Cl, SCl2, PCl3, H2O, NH3, HF, H2O2, alcohols, polar
compounds
London Dispersion Forces
• H2, Cl2, CO2, N2O4, CH4, paraffin wax, polar and non polar
substances!
NEW WORD!!!
• Volatile- Volatile is how easily a substance
evaporates.
– High volatility-Evaporates very fast.
– Low volatility-Evaporates slowly.
– Can you smell all substances that have evaporated?
• Smell
– In order to smell something, the aroma (esters, chemicals) must
reach your nose and you must have the receptors to interpret
that smell.
Procedure
• Procedure:
• 1. Place a penny face down on a weighing boat.
• 2. CAREFULLY add drops of water on top (pipet
straight up and down). Your goal is to put as
many drops on top of the penny without any
water falling into the weighing boat.
• 3. Count the number of drops that the penny
was able to HOLD. RECORD.
Procedure
• 4. Dry the penny with a paper towel. Place
the water in the sink.
• 5. Repeat the process. Record.
• 6. Repeat procedures using isopropyl alcohol.
You can put the isopropyl alcohol down the
sink as well.
• 7. Repeat procedures using acetone. Place
the “waste” acetone in the “waste container”
(with a lid).
• Conclusions
– Hydrogen bonding is the strongest type of
intermolecular force.
– A non polar molecule can only have london dispersion
forces.
– A polar molecule can have london dispersion forces,
and dipole forces.
– Certain polar molecules like water and ammonia can
have london dispersion forces, dipole forces, and
hydrogen bonding.
– The stronger the intermolecular force, the LESS
volatile a substance is.
– The weaker the intermolecular force, the MORE
volatile a substance is.
– You don’t always smell volatile substances!!!!!