Transcript Behavior of Gases C-5: The student will demonstrate an

Behavior of Gases
• C-5: The student
will demonstrate an
understanding of
the structure and
behavior of the
different phases of
matter.
C-5.1 Explain the effects of the intermolecular
forces on the different phases of matter.
EQ 1. What are the phases
of matter?
EQ 2. What are
intermolecular (or
interparticle forces)?
EQ 3. In the phases of
matter listed above, are
these forces strong,
intermediate, or weak?
Phases of Matter
• Kinetic model of solids: Strong forces between
particles keep structure rigid. They are in motion but
cannot move past one another. Crystal lattice is the
three-dimensional arrangement of the particles in a solid.
• Kinetic model of liquids: Interparticle forces maintain
their volume, but not their shape. Particles are so close
together they slide past one another. i.e. magnetized
marbles.
• Kinetic Model of gases: Interparticle forces do not
maintain shape or volume. Particles “bounce” off each
other. Gases do not lose kinetic energy as they bounce
off each other or the container. The collisions are
elastic.
Other phases of Matter?
• Other forms of matter: matter that
looks like a solid or gas but
behave like a liquid. These forms
are plasmas, liquid crystals, and
amorphous materials.
• What are some examples of the
other forms of matter?
•
•
•
Liquid crystals - laptop, calculators
Plasma – ionized gas, i.e. sun, stars, fluorescent
lights
Amorphous Materials – disjointed, and incomplete
crystal lattice. i.e. peanut butter, wax, cotton candy
EQ4. What is the Kinetic Molecular
Theory for gases?
• Kinetic Theory of Matter: states that all submicroscopic
particles of all matter are in constant random motion.
The energy of moving objects is called kinetic energy.
• Kinetic Model of gases: Gases do not lose kinetic
energy as they bounce off each other or the container.
The collisions are elastic.
• A gas with particles in constant random motion in which
they have no attraction for each other are called ideal
gases. Nearly all gases are ideal except when they are
at very low temperatures or very high pressures.
Pressure is the force acting on a unit area.
Indicator C-5.2
• Explain the behaviors of gas; the
relationship among pressure, volume, and
temperature; and the significance of the
Kelvin (absolute temperature) scale, using
the kinetic-molecular theory as a model.
EQ 5. What is pressure, volume, and
temperature?
• Pressure - _____
_______________
• Volume - _______
______________
• Temperature- ____
________________
EQ 6. How do pressure, volume and
temperature effect gases?
• Pressure is what keeps the balloon inflated.
• Atmospheric Pressure is 760 mm of Hg = 1atm
(is the pressure on us now.)
• If pressure increases, the volume decreases. If
pressure decreases, the volume____?____.
• List the other pressure units:
•
If pressure is doubled, the volume decreases by half.
Pressure Units
• 1 atm = 760 mmHg (torr) = 101.3 kPa = 14.7 psi
• Conversions:
– What pressure, in kPa, atm, and psi does a
gas exert at 246 mm Hg?
–
246 mm Hg x 101.3 kPa = 32.8 kPa
760 mm Hg
246 mm Hg x 1 atm =
0.324 atm
760 mm Hg
246 mm Hg x 14.7 psi = 4.76 psi
760 mmHg
Pressure conversions. (Cp -p. 387. TP – p. 339 )
EQ 6. How does pressure, volume and
temperature affect gases?
• Gas is heated (temperature increases) – average kinetic
energy increases, particles’ speed increases.
• Gas is cooled (temperature decreases) – average kinetic
energy decreases, particles’ speed decreases.
• How do we measure temperature?
Three scales: Fahrenheit, Celsius, and Kelvin
°C = (° F-32) x 0.556
°F = (°C x 1.8) + 32
Tk = (Tc + 273) K
p. 78 CP TP p.66-71
Tc = (Tk - 273) °C
Temperature Conversions
• Convert 60.4 °C to Kelvin
– Tk = (Tc + 273) K
– Tk = 60.4 + 273) K = 333 K
Convert 76.5 °F to Kelvin
°C = ( °F-32) x 0.556
°C = (76.5 °F -32) x 0.556 = 24.7
Tk = 24.7 °C + 273 = 298 K
EQ7: What is absolute (zero)
temperature?
• Absolute Zero – the temperature at
which a substance has no kinetic
energy. No particles are moving.
This is:
0 Kelvin, -273.15 °C, -459.67 °F.
Why is the Kelvin scale important?
EQ7: What is absolute (zero)
temperature?
Why is the Kelvin scale important?
It is the temperature at which the average
kinetic energy of gas particles would be
theoretically zero. Thus absolute zero.
EQ8. How are the relationships
described mathematically?
• Boyle’s Law:
P1 x V1 = P2 x V2
If pressure is doubled, the volume decreases by
half.
•
Sample problem 3, p.388.
• Charles’s Law
V1 = V2 , pressure and mass is constant
T1
T2
If temperature is increased, then volume
increases.
Boyle’s Law:
• The pressure-volume
relationship:
Pressure and volume
is inversely related,
temperature and
mass is constant.
Charles’s Law
• The temperature –
volume relationship:
• V1 = V2 ,
• T1
T2
• V1 xT2 = V2 xT1
• Pressure and mass is
constant
If temperature increase,
then volume increases.
Sample problem 5, p.393(cp)
Combined Gas Law:
•
P1 x V1 = P2 x V2
T1
T2
• P1V1T2 = P2V2T1
• This gas law is a
combination of which
gas laws?
Standard Temperature and
Pressure
(STP)
• Standard Temperature = 0º C = 273K
• Standard Pressure = 1 atm = 14.7 psi
=760 mm Hg (torr) = 101.3 kPa
Ideal Gas Law:
• PV = nRT
• R (constant) =(8.31 kPa ∙ L) not variables
•
mol ∙ K
• P = pressure (kPa)
V = volume (Liters)
• n = # of mole
T = temperature (Kelvin)
Indicator C-5.4
• Illustrate and interpret
heating and cooling
curves (including how
boiling and melting
points can be
identified and how
boiling points vary
with changes in
pressure).
EQ9. How can boiling points and melting
points be identified from graphs?
Melting and Boiling points of Water
120
100
Temp. (Celsius)
80
60
40
20
0
-20
-40
Time (min.)
• When the
temperature stops
increasing. (The line
flattens.)
• Define Heat of
Fusion.
• Define Heat of
Vaporation.
Heating and Cooling curve of
Acetone
• Graph the following points:
Time (min.) vs
0
5
10
15
20
30
35
40
45
50
Temperature, °C
-115
-95.35
-95.35
-95.35
0 °C
18
36
56.24
56.24
56.24
Degrees Celsius
Heating Curve of Acetone
80
60
40
20
0
-20 0
-40
-60
-80
-100
-120
-140
10
20
30
40
Time (min.)
50
60
Temp. Celsius
Cooling Curve of Acetone
80
60
40
20
0
-20 0
-40
-60
-80
-100
-120
-140
10
20
30
Time (min.)
40
50
EQ10: How does pressure affect
boiling points?
• Boiling Point – the temperature of a substance
when its vapor pressure equals the pressure
exerted on the surface of the liquid.
• Vapor Pressure – the pressure of a substance in
equilibrium with its liquid. Particles are evaporating and
condensing at the same rate.
• Low vapor pressure substances have high boiling
points. i.e. mercury, syrup. Interparticle forces are
strong.
• High vapor pressure substances have low boiling
points. i.e. ethanol, perfume. Interparticle forces are
weak.
EQ10: How does pressure affect
boiling points?
• If pressure
increases, the
temperature
increases. Thus,
the boiling point of a
substance will
increase.
•
What cooking device uses this
concept?
Answers
EQ 1. Solid, liquid, gases,
etc.
EQ 2. - attraction between
the molecules.
EQ 3. Solids - strong,
Liquids - intermediate,
Gases - weak
EQ 5. What is pressure, volume, and
temperature?
• Pressure is the force
acting on a unit area.
• Volume is the space
occupied by a sample
of matter.
• Temperature is the
measure of the
average kinetic
energy of particles.
Definitions
• Heat of Fusion – the amount of energy
needed to change a material from the solid
state to the liquid state.
• Heat of Vaporation – the amount of energy
needed to change a material from the
liquid to the gas state.