Matter can exist in three main states - solid, liquid, and gas. In solids, the particles are tightly packed in a fixed arrangement, while in liquids they are more loosely packed but still in contact. Gas particles are widely spaced and move freely. A key difference between the states is that solids have a definite shape and volume, while liquids take the shape of their container but have a definite volume. Gases fill their container completely. Phase changes between states require energy. Melting and vaporization are endothermic processes that absorb energy to overcome intermolecular forces, while freezing and condensation release energy. Phase changes can occur through heating, cooling, or changes in pressure.

1. Prepared by :-
Abhishek

2. Observing the Natural World of Matter
What Is Matter?
Matter is the material or “stuff” everything is made of.
What are you doing if you are observing matter?
Observing matter means to carefully explore all of its properties.
Look around the room and identify some matter.
What are some physical properties matter can have?
Color, texture, odor, shape…
What are two properties that all matter share?
All matter has mass and takes up space.
What are the three states of matter?
solid, liquid, and gas

3. Solid, Liquid, Gas
(a) Particles in solid (b) Particles in liquid (c) Particles in gas

4. Ice
H2O(s) Ice
Photograph of ice model Photograph of snowflakes

5. Liquid
H2O(l) Water
In a liquid
• molecules are in
constant motion
• there are appreciable
intermolecular forces
• molecules are close
together
• Liquids are almost
incompressible
• Liquids do not fill the
container

6. Gas
H2O(g) Steam

7. Liquids
The two key properties we need to describe are
EVAPORATION and its opposite CONDENSATION
add energy and break intermolecular bonds
EVAPORATION
release energy and form intermolecular bonds
CONDENSATION

8. States of Matter
Solid Liquid Gas
Holds Shape
Fixed Volume
Shape of Container
Free Surface
Fixed Volume
Shape of Container
Volume of Container
heat heat

9. Some Properties of Solids, Liquids, and Gases
Property Solid Liquid Gas
Shape Has definite shape Takes the shape of Takes the shape
the container of its container
Volume Has a definite volume Has a definite volume Fills the volume of
the container
Arrangement of Fixed, very close Random, close Random, far apart
Particles
Interactions between Very strong Strong Essentially none
particles

10. • To evaporate, molecules must have sufficient
energy to break IM forces.
• Molecules at the surface break away and
become gas.
• Only those with enough KE escape.
• Breaking IM forces requires energy. The process of
evaporation is endothermic.
• Evaporation is a cooling process.
• It requires heat.
Evaporation

11. Change from gas to liquid
Achieves a dynamic equilibrium with vaporization in
a closed system.
What is a closed system?
A closed system means matter
can’t go in or out. (put a cork in
it)
What the heck is a “dynamic
equilibrium?”
Condensation

12. As time goes by the rate of vaporization remains
constant but the rate of condensation
increases because there are more molecules
to condense.
Equilibrium is reached when:
Rate of Vaporization = Rate of Condensation
Molecules are constantly changing phase “dynamic”
The total amount of liquid and vapor remains constant
“equilibrium”
Dynamic Equilibrium

13. • Vaporization is an endothermic process - it
requires heat.
• Energy is required to overcome intermolecular
forces
• Responsible for cool earth
• Why we sweat
Vaporization

14. Energy Changes Accompanying Phase Changes
Solid
Liquid
Gas
Melting Freezing
Deposition
CondensationVaporization
Sublimation
Energyofsystem

15. Density & Specific gravity
Density:-The density of a material is equal to its mass divided by its volume and has units of
𝑘𝑔𝑚−3
.
It is of two types:-
 Bulk Density
 Particle Density
What is porosity?
Surface Gravity:
SG = density of liquid / density of water

16. Viscosity
Viscosity may be thought of as a liquid’s internal resistance to
flow. A liquid can be envisaged as having a series of layers
and when it flows over a surface, the uppermost layer flows
fastest and drags the next layer along at a slightly lower
velocity, and soon through the layers until the one next to the
surface is stationary.

17. Van der Waals Forces and the Properties of
Liquids
• Viscosity increases with increasing intermolecular forces because
increasing these forces increases the resistance to flow.
– Other factors, such as the possibility of
molecules tangling together, affect viscosity.
– Liquids with long molecules that tangle together
are expected to have high viscosities.

18. Continue…
Pseudo plastic fluid – Viscosity decreases as the shear rate increases
(e.g. emulsions, and suspensions such as concentrated fruit juices and
puries)
Dilatant fluid – Viscosity increases as the shear rate increases. (This
behaviour is less common but is found with liquid chocolate and corn
flour suspension.)
Binghamor Casson plastic fluids – There is no flow until a critical
shear stress is reached and then shear rate is either linear (Bingham
type)or non-linear ( Casson type)(e.g. tomato ketchup)
Thixotropic fluid – The structure breaks down and viscosity decreases
with continued shear stress ( mostcreams)
Rheopectic fluid – The structure builds up and viscosity increases
with continued shear stress ( e.g.whippingcream)

19. Surface Tension
• Surface tension is the
tendency for liquid
surface to contract.
• Depends on attractive
forces
• Compounds that
interfere with the forces
and reduce surface
tension are called
surfactants.

20. Van der Waals Forces and the Properties of
Liquids
• Surface tension increases with increasing intermolecular forces.
– Surface tension is the energy needed to reduce
the surface area of a liquid.
– To increase surface area, it is necessary to pull
molecules apart against the intermolecular forces
of attraction.

21. The molecular basis of surface tension.
hydrogen bonding
occurs in three
dimensions
hydrogen bonding
occurs across the surface
and below the surface
the net vector
for attractive
forces is downward

22. Shape of water or mercury meniscus in glass.
adhesive forces
stronger
cohesive forces
H2O
capillarity
Hg

23. The striking beauty of crystalline solids.

24. portion of a 3-D lattice
The crystal lattice and the unit cell.
lattice point
unit
cell
portion of a 2-D lattice
unit
cell

25. Phase Changes

26. Phase Changes
solid liquid gas
melting
freezing
vaporizing
condensing
sublimination
Energy absorbed
Energy released

27. Quick Review to what we have studied so
far.