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CHEMISTRY U4 AOS1 > Properties > Flashcards

Flashcards in Properties Deck (14):
1

define: polar bonds

when one atom is more electronegative than other other so electrons are pulled towards it, forming dipole positive and negative.

2

how are non polar bonds formed

only when the bond is between the same elements

3

how can polar bonds form a non polar molecule?

if the molecule is symmetrical/polarity cancels out.

4

define: dispersion forces

present in all covalent molecules due to their ability to form an instantaneous dipole (due to random movement of electrons)

5

as molecules get bigger

more dispersion forces can form...

6

define: dipole dipole bonds

attraction between positive negative dipoles.
greater the difference in dipoles the stronger the bonds.

7

define: h bond

attraction between hydrogen and the most electronegative elements (FON)

8

ion dipole bonds

between charge on an ion and the dipole of a polar bond.

9

describe boiling point

changing from a liquid to a gas involves breaking intermolecular bonds. The stronger these bonds, the more difficult to break and the higher BP.

10

strength of intermolecular bonds?

disp-dipole/dipole-hydrogen-iondipole

11

effect of shape on bp?

having branches means molecules cant pack as thighly together. results in weaker (??) disp forces and lower bp

12

define: viscosity

measure of a liquid’s resistsance to flow.
stronger the intermolecular forces (bonding/size/sahpe) the more viscous.

13

describe: flashpoint

the lowest temp at which the vapour of a liquid fuel will ignite when an ignition source (eg. flame) is applied.
As the temp of a liquid fuel increases, the conc of its vapour increases. At a certain concentration (hence temp) there’ll be enough vapour mixed with air for the fuel to ignite.
In order to become a vapour the fuel needs to boil – therefore flashpoint is indicative of boiling point (bonding/size/shape)

14

how do we differentiate bt bp's

whether things can form hydrogen, dipole-dipole or disp forces - determines strength
alkeanes, alkenes, alkynes
aldehydes, ketones, esters
alcohols, carb acids, amines, amides