Liquids are denser than gases and do not change much in volume when pressure is applied. Liquids and solids are known as condensed states of matter. The conversion of a liquid to a gas is called vaporization through evaporation or boiling. Evaporation occurs at the surface and increases with temperature as the kinetic energy of particles increases. Boiling occurs when the vapor pressure equals the external pressure and particles throughout the liquid vaporize. Solids have orderly, fixed particle arrangements that determine properties like melting points based on bonding type. Phase diagrams show conditions where substances exist as solids, liquids or gases.

1. •The Nature of Matter

2. Liquids
• The ability of gases and liquids to flow
allows then to conform to the shape of
their containers.
• Liquids are much more dense then gases.

3. More on liquids….
»Increasing the pressure on a liquid
has hardly any effect on its volume.
(The same is true of solids).
»For that reason, liquids and solids
are known as condensed states of
matter.

4. Evaporation & Vaporization
• The conversion of a liquid to a gas or
vapor is called vaporization.
• When such a conversion occurs at the
surface of a liquid that is not boiling, the
process is called evaporation.

6. Key Concept
• During evaporation, only those
surface molecules with a certain
minimum kinetic energy can escape
from the surface of the liquid.

7. More on Evaporation….
• Liquid evaporates faster when heated.
This is because heating a liquid increases
the average kinetic energy of its particles.
• As evaporation occurs, the particles with
the highest kinetic energy escape first.
• Evaporation is a cooling process!!

8. Vapor Pressure
Vapor (Gas)Liquid
evaporation
Condensation

9. • An increase in temperature
of a contained liquid
increases the vapor
pressure.

10. Boiling Point
vapor pressure = external pressure
• When a liquid is heated to a temperature
at which particles throughout the liquid
have enough kinetic energy to vaporize,
the liquid begins to boil.
• Because atmospheric pressure is lower at
higher altitudes, boiling points decrease at
higher altitudes.

12. • Although vapor has the same kinetic
energy as the liquid, its potential (or stored
energy) is much higher.
»Thus a burn from steam is more
severe than one from an equal mass
of boiling water at the same
temperature.

13. The Nature of Solids
• The general properties of solids reflect the
orderly arrangement of their particles and
the fixed locations of their particles.

14. Melting Point
Solid Liquid
Melting
Freezing

15. Crystal Structure
• The type of bonding that exists between
particles in crystals determines their
melting points.
» Not all solids melt however.
» Wood and cane sugar for example,
decompose when heated.

16. Changes of State
• Sublimation is the change of a substance
to a vapor without passing through the
liquid state.

17. Phase Diagrams
• A phase diagram gives the conditions of
temperature and pressure at which a
substance exists as a solid, liquid and gas
(vapor).

19. Phase Diagram Cont…
• The Triple Point describes the only set of
conditions at which all three phases can
exist in equilibrium with one another.
• A decrease in pressure lowers the boiling
point and raises the melting point
• An increase in pressure will raise the
boiling point and lower the melting point.