SCH 3U1
ATTRACTIVE FORCES
There are different types of forces that exist between
molecules and particles. The strength of these particles
determines the _______ of the substance. For example, if a
substance is solid that means the particles are locked beside
each other tightly. This is a ______ force. In the case of gases
the forces are ______. The particles themselves move about
_______ and when they collide they rebound off each other.
Electrostatic Force: This force is referred to as an
____________ interaction or an ionic bond. It is the result of a
positive and a negative charge wanting to pull closer to each
other. These particles usually form ionic ______. Strong Force.
Hydrogen Bonding:
Definition - A hydrogen bond is an _________________
in which a hydrogen atom that is bonded to an electronegative
atom (_______) is attracted to an unshared pair of _______ on
another electronegative atom. This combination creates an
attraction (not a bond) that is much _______ than a dipole
force or London force.
Hydrogen bonds are like any other attractive (intermolecular)
forces because the attractions are ___________ in nature.
Water is one molecule that displays hydrogen bonding. Because
water is a polar molecule, individual water molecules _______
each other by _________ and hydrogen bonds. In order to boil
water these numerous interactions must be broken and this
requires a lot of _______. This energy needed gives water a
much ______ boiling point than would be expected of a molecule
of its size and bond type.
..
..
..
:O--H - - - :O--H - - - :O--H H
|
|
|
|
H
H
H - - - :O--H
The hydrogen bond is not only found in water but generally in
hydrogen compounds that have elements with high __________.
The bonds N-H, O-H and F-H all display hydrogen bonding. Each
of the compounds water, ammonia and hydrogen fluoride have a
much _______ boiling point than expected. Intermediate Force.
Dipole-Dipole Force: This force occurs when a polar
molecule interacts with a polar molecule. A polar molecule means
that the electrons are shifted ______ the more electronegative
element, eg. HCl. In this molecule the electrons are pulled toward
the ______, making the chlorine (slightly) negative and the
hydrogen positive. The hydrogen chloride molecule is said to have
a dipole.
+ -
+ -
+ -
+
-
+ -
+ -
H-Cl --- H-Cl --- H-Cl --- H-Cl --- H-Cl --- H-Cl
The three dashes indicate the dipole force that exists.
(Analogy: a layer of butter between two oreo cookies.) Weak
force.
London Forces: In an atom or a non-polar molecule the electron
cloud is ___________. However, the electrons have a random
motion within the electron cloud. In any one instant there may be
_____ electrons on one side of the cloud. This will give it a
(brief and slight) charge. This can ______ a charge in a
neighbouring particle. These interactions that form keep the
liquid together and have to be _______ before it becomes a gas.
Weak force.