Earth and life science

1. Bella B. Velasquez
SHS Teacher II
EFFECTS OF INTERMOLECULAR
Forces on Properties of
Substances

2. Strength of intermolecular forces
strongest
• Ion – dipole
• H-bonding
• Dipole-dipole
• Dipole-induced dipole
• London dispersion force/
Van der Waals
weakest

3. Ion-ion interaction
• Exists between oppositely charged ions. It
occurs between ionic compounds.
• Have high melting and boiling points
• Strongest intermolecular force

4. Hydrogen bond
• Very strong dipole-dipole interaction.
• Occurs in polar molecules containing H and
any one of the highly electromagnetic
elements, in particular F,O or N

5. Dipole-dipole interaction
• Occurs between polar molecules
• Due to partial positive pole and partial
negative pole of the molecule

6. Dispersion force or London Force
• Present in all molecules.
• The only force present in non-polar molecules
• Without dispersion force substances would not be
able to condense to liquid and solid phase.

8. Properties of substances affected by
intermolecular forces
• Surface tension – the amount of energy required
to stretch the surface area of liquids
Example:
• capillary action- the ability of liquid molecules
to move against gravity
• cohesion-intermolecular attraction between like
molecules
• adhesion-attraction between unlike molecules

9. The stronger the intermolecular force
possessed by molecules, the higher
the surface tension of the substance

10. • Cohesion: Water is attracted to water
• Adhesion: Water is attracted to other substances.
solids have high cohesive properties so they do not
stick to the surfaces they come in contact

12. Concave meniscus Convex meniscus
When there is stronger
adhesive force between the
container and the
liquid than the liquid’s
molecules.
When there is stronger
cohesive force between
liquid’s molecules than the
adhesive force between the
liquid and the container
DRAW DRAW

13. Viscosity
Resistance of a liquid to flow
The greater the viscosity of liquid, the more
slowly it flows
Stronger intermolecular force - highly viscous
More viscous- thicker consistency
Which is more viscous?
______________ ______________
or or

14. Water and Paper clips
• Objective:
• To be able to demonstrate intermolecular
force through surface tension.

15. Water and Paper Clips
Procedure:
• Fill a glass to the brim with water without
spilling.
• Add paper clips into the water. Count how
many paper clips can be added without the
water spilling out.
• Create a “boat” using a bent paper clip with a
small piece of paper attached to it to serve as
a mast. Gently suspend it on top of a liquid
and watch it float.

16. • Observe closely where the clip and the water
meets.
• What do you call the interaction between the
water and the paper clips?
• _________________________________