Transcript Chemistry: Matter and Change

Section 3.2 Assessment
When one substances turns into another,
what kind of change has taken place?
A. chemical reaction
B. physical reaction
D
A
0%
C
D. nuclear reaction
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. extensive reaction
Section 3.2 Assessment
The law of conservation of mass states
that:
A. Matter can be created and destroyed.
B. Matter can be created but not destroyed.
0%
0%
D
0%
A
B
C
D
C
0%
A
D. The products of a reaction must
have the same mass as the
reactants.
A.
B.
C.
D.
B
C. The products of a reaction always
have a greater mass than the
reactants.
Section 12.4 Phase Changes
• Explain how the addition
and removal of energy
can cause a phase
change.
• Interpret a phase
diagram.
phase change: a
change from one state
of matter to another
Section 12.4 Phase Changes
(cont.)
melting point
freezing point
vaporization
condensation
evaporation
deposition
vapor pressure
phase diagram
boiling point
triple point
Matter changes phase when energy is
added or removed.
Phase Changes That Require Energy:
Melting, Vaporization, Sublimation
• Melting occurs when heat flows into a solid
object.
• Heat is the transfer of energy from an object
at a higher temperature to an object at a
lower temperature.
Phase Changes That Require Energy (cont.)
• When ice is heated, the temperature of ice
will increase up until the ice reaches its
melting point.
• At its melting point, the energy absorbed by
the ice goes into breaking the hydrogen
bonds that hold the water molecules
together.
• When the bonds break, the particles move
apart and ice melts into water. This process
will continue until all the ice is melted.
• The melting point of a crystalline solid is the
temperature at which the forces holding the
crystal lattice together are broken and it
becomes a liquid.
Phase Changes That Require Energy (cont.)
• Particles with enough energy escape from
the liquid and enter the gas phase.
Phase Changes That Require Energy (cont.)
• Vaporization is the process by which a
liquid changes to a gas or vapor.
• Evaporation is vaporization only at the
surface of a liquid.
Boiling:
vaporization
that occurs
throughout
the liquid.
In an open container of water, all the
molecules of water will eventually evaporate.
In a closed container, water vapor will
collect over the liquid.
Phase Changes That Require Energy (cont.)
• In a closed container, the pressure exerted
by a vapor over a liquid is called vapor
pressure.
Phase Changes That Require Energy (cont.)
• The boiling point is the temperature at
which the vapor pressure of a liquid equals
the atmospheric pressure.
At this point,
molecules
throughout the
liquid have the
energy to
vaporize.
Phase Changes That Require Energy (cont.)
• Sublimation is the process by which a
solid changes into a gas without becoming
a liquid.
•What do you know that goes through
sublimation?
Phase Changes That Release Energy:
Freezing, Condensation, Deposition
• As heat flows from liquid water to the
surroundings, the particles lose energy. As
they lose energy, the molecules go back
into their fixed positions. Freezing is the
reverse of melting.
• The freezing point is the temperature at
which a liquid is converted into a crystalline
solid.
Phase Changes That Release Energy (cont.)
• As water vapor loses energy, the velocity of
the particles decreases. Water molecules
bond, releasing energy as they do so.
• The process by which a gas or vapor
becomes a liquid is called condensation
• Condensation is the reverse of evaporation.
• Deposition is the process by which a gas
or vapor changes directly to a solid, and is
the reverse of sublimation.
– Frost is an example of deposition.
– Snowflakes are also formed in the upper
atmosphere by deposition of ice crystals.
Phase Diagrams
• A phase diagram is a graph of pressure
versus temperature that shows in which
phase a substance will exist under different
conditions of temperature and pressure.
Phase Diagrams (cont.)
• The triple point is the point on a phase
diagram that represents the temperature
and pressure at which all three phases of a
substance can coexist.
Phase Diagrams (cont.)
• The phase diagram for different
substances are different from water.
16.1
Kinetic Theory
Heating Curve of a Liquid
• This type of graph is
called a heating curve
because it shows the
temperature change of
water as thermal energy,
or heat, is added.
• Notice the two areas on the
graph where the
temperature does not
change.
• At 0°C, ice is melting.
• At 100°C, water
vaporizes.
Section 12.4 Assessment
The addition of energy to water molecules
will cause them to ____.
A. freeze
B. change to water vapor
D
A
0%
C
D. move closer together
A. A
B. B
C. C
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0%
0%
D. D
B
C. form a crystal lattice
Section 12.4 Assessment
The transfer of energy from one object to
another at a lower temperature is ____.
A. heat
B. degrees
D
A
0%
C
D. electricity
A. A
B. B
C. C
0%
0%
0%
D. D
B
C. conductivity
Section 15.1 Energy
• Define energy.
• Distinguish between potential and kinetic energy.
• Relate chemical potential energy to the heat lost or
gained in chemical reactions.
• Calculate the amount of heat absorbed or released by
a substance as its temperature changes.
temperature: a measure of the average kinetic
energy of the particles in a sample of matter