STEM Lesson

1. THE KINETIC MOLECULAR
THEORY OF SOLIDS AND
LIQUIDS

2. • THE ARRANGEMENT OF PARTICLES IN SOLID, LIQUIDS,
AND GASES EXPLAINING THE DIFFERENT PROPERTIES.
• THE PARTICLE IN SOLIDS ARE CLOSELY PACKED AND ARE
FREE TO MOVE, AND THEY CAN ONLY VIBRATE.
• SOLID HAS FIXED VOLUME AND SHAPE AND HAVE HIGH
DENSITY
• LIQUID PARTICLES HAVE SUFFICIENT ENERGY TO
OVERCOME THEIR ATTRACTIVE FORCES AND THE
PARTICLES SLIDE AND ROLL ON TOP OF EACH OTHER.
• LIQUIDS FLOW AND HAVE FIXED VOLUME BUT NO FIXED
SHAPE

3. INTERMOLECUL
AR FORCES
• IS THE FORCE OF ATTRACTION
BETWEEN NEIGHBORING
MOLECULES.
• FORCES OF ATTRACTION-ARE
CAUSED BY THE FORMATION OF
BOND BETWEEN ATOM.
• IONIC BOND- IS FORMED WHEN
THERE IS A TRANSFER OF
ELECTRONS FROM METAL TO A
NON METAL, FORMING OPPOSITE
CHARGE PARTICLES.
• IONIC COMPOUND- EXIST AS
SOLIDS AT ROOMS TEMPERATURE,
AND SO DO METALLIC ATOMS.
• COVALENT BOND- IS FORMED
WHEN THERE IS A SHARING OF
ELECTRONS BETWEEN TWO OR
MORE NON METALS.

4. DISPERSION FORCES
Are a type of intermolecular force of attraction.
Dispersion forces are present in all molecular substances
These are forces between induced dipoles.
Induced dipole-is created when there is temporary shift of electrons in
an atom or molecule, causing the separation of charges where the end
becomes more positive than the other hand.

5. DIPOLE-DIPOLE FORCES
• THE DISPERSION OF FORCES FORMED BETWEEN
NEIGHBORING MOLECULES OF PERMANENT
DIPOLES.
• POLAR MOLECULES-MOLECULES WITH
PERMANENT DIPOLES AND HAVE AN UNEVEN
SHARING OF ELECTRONS AND THE
ELECTRONEGATIVITY DIFFERENCE BETWEEN THE
ATOMS IS GREATER THAN 0.4.
• BOILING POINTS OF THE POLAR MOLECULES ARE
HIGHER THAN THOSE OF NONPOLAR BECAUSE
THERE IS ONLY INDUCED DIPOLE OR TEMPORARY
DIPOLES IN NONPOLAR MOLECULES.

6. ION-DIPOLE
FORCES
• AN ION-DIPOLE
INTERMOLECULAR FORCE
OF ATTRACTION REFERS TO
THE INTERACTION BETWEEN
AN ION AND A POLAR
MOLECULE.
• EX. IONIC COMPOUNDS
DISSOLVED IN POLAR
COMPOUNDS. THE ION-
DIPOLE FORCE INCREASE IN
STRENGTH WHEN THE
CHARGE OF THE ION AND
THE MAGNITUDE OF THE
DIPOLE BECOME GREATER.

7. HYDROGEN BOND
Is a term used for polar molecules with a
large dipole because OF VERY HIGH
ELECTRONEGATIVITY DIFFERENCE.
THIS IS TRUE FOR MOLECULES CONTAINING
O-H, N-H, AND H-F BONDS.
COMPOUNDS CONTAINING THIS BONDS
HAVE HIGHER BOILING POINTS THAN
MOLECULES WITH DIPOLE-DIPOLE FORCES.

8. PROPERTIES OF
LIQUIDS AND
INTERMOLECUL
AR FORCES
BASSED ON THE KINETIC MOLECULAR THEORY,
LIQUIDS HAVE THE FOLLOWING GENERAL PHYSICAL
PROPERTIES:
A. PARTICLES SLIDE AND ROLL ON TOP OF ONE
ANOTHER.
B. PARTICLE HAVE LIMITED MOVEMENT AND, HENCE,
THEY FLOW
C. MODERATELY HIGH DENSITY AND DIFFUSABILITY
D. HAVE FIXED VOLUME BUT NO FIXED SHAPE.

9. SURFACE TENSION
• REFERS TO THE FORCE THAT CAUSES THE MOLECULES ON THE SURFACE
OF A LIQUID TO BE PUSHED TOGETHER AND FORM A LAYER.
• THE SURFACE MOLECULES LOCK INTO A THIN LAYER OF ELASTIC
MEMBRANE BECAUSE THEY ARE ALL ATTRACTED WITH EACH OTHER
AND ARE BEING PULLED BY THE MOLECULES AT THE CENTER.
• SURFACE TENSION EXPLAIN WHY DROP OF LIQUID IS SPHERICAL IN
SHAPE.
• IT ALSO EXPLAINS WHY WATER STRIDER CAN WALK ON THE SURFACE OF
THE WATER
• THE STRONGER THE INTERMOLECULAR FORCE ATTRACTION, THE
GREATER THE SURFACE TENSION, HOWEVER, AN INCREASE IN
TEMPERATURE DECREASE SURFACE TENSION.

10. VISCOSITY
• IS THE RESISTANCE OF FLUID TO
FLOW.
• A SUBSTANCE THAT FLOWS READILY
HAS LOW VISCOSITY.
• VISCOSITY- IS A MEASURE OF THE
SUBSTANCE’S INTERMOLECULAR
FORCE OF ATTRACTION(IMFA). IF
THE IMFA IS STRONG, THE LIQUID
WILL HAVE HIGH VISCOSITY
BECAUSE IT WILL HAVE A HIGH
RESISTANCE AGAINST FLOWING. THE
GREATER THE IMFA, THE HIGHER
THE VISCOSITY, AND THE LESS
READILY THE LIQUID FLOWS.
• TEMPERATURE ALSO AFFECT
VISCOSITY, THE HIGHER THE
TEMPERATURE, THE LOWER THE
LQUID VISCOSITY.

11. VAPOR PRESSURE AND BOILING POINT
• THE VAPOR PRESSURE OF A LIQUID
IS THE PRESSURE OF THE VAPOR
RESULTING FROM EVAPORATION
OF ALIQUID ABOVE A SAMPLE OF
THE LIQUID IN A CLOSED
CONTAINER.
• IF A LIQUID HAS WEAK
INTERMOLECULAR FORCES OF
ATTRACTION, THE ESCAPING
TENDENCY OF THE MOLECULES IS
HIGH.