Download Understanding KMT using Gas Properties and States of Matter

Understanding KMT using Gas
Properties and States of Matter
Learning Goals: Students will be able to describe matter in
terms of particle motion. The description should include
•Diagrams to support the description.
•How the particle mass and temperature affect the image.
•How the size and speed of gas particles relate to everyday
objects
•What are the differences and similarities between solid,
liquid and gas particle motion
What is KMT?
1.
Gases are composed of a large number of particles that behave like hard,
spherical objects in a state of constant, random motion.
2.
These particles move in a straight line until they collide with another
particle or the walls of the container.
3.
These particles are much smaller than the distance between particles.
Most of the volume of a gas is therefore empty space.
4.
There is no force of attraction between gas particles or between the
particles and the walls of the container.
5.
Collisions between gas particles or collisions with the walls of the
container are perfectly elastic. None of the energy of a gas particle is lost
when it collides with another particle or with the walls of the container.
6.
The average kinetic energy of a collection of gas particles depends on
the temperature of the gas and nothing else.
If you have a bottle with Helium & Nitrogen at room
temperature, how do the speed of the particles
compare?
A. All have same speed
B. The average speeds are
the same
C. Helium particles have
greater average speed
D. Nitrogen particles have
greater average speed
Light and heavy gas at same
temperature 300K
Speed of each particle varies!!
What happens if you add
energy using the heater?
A. All atoms speed up
B. All atoms speed up about the
same
C. The lighter ones speed up
more
D. The heavier ones speed up
more
answer
Which is most likely oxygen gas?
A
B
C
Which is most likely liquid water?
A
B
C
Explain what happens to the behavior
of the gas particles when volume is
decreased and why.
• Speed? Why?
• Temp? Why?
• Pressure? Why?
The total KE of a substance is equal to
the thermal energy of the substance.
• Predict: What happens to the temperature when
molecules speed up?
• Predict: What happens to the temperature when
more molecules are added?
• Do the results seem reasonable?
• Tub of hot water vs glass of hot water…
• What might thermal equilibrium mean in terms
of the gas and the thermometer?
• What indirect measurement is a good indicator of
the thermal energy of a substance?
System Examples
• Open: Matter and energy exchanges w/
environment.
• Closed: Energy exchanges w/ environment.
• Isolated: No exchanges at all w/ environment.
• http://chemwiki.ucdavis.edu/Physical_Chemis
try/Thermodynamics/A_System_And_Its_Surr
oundings
Why do we use the Kelvin scale to
measure temperature in
thermodynamics?
•
•
•
•
What is the definition of cold?
What is the definition of hot?
Which is hotter, book or box?
What comprised “the system” in the Gas
Properties simulation?
• Did energy enter or leave this system? Proof?
Question:Which graph best represents the relationship
between the average kinetic energy (Kavg) of the
random motion of the molecules of an ideal gas and its
absolute temperature (T)? Hint: Consider the Eqn.
Answer: (2) since Kavg is a linear
function of absolute temperature T.
Temp is directly related to
average KE of motion of the
molecules in a sample.
3
𝐾𝐸𝐴𝑣𝑔 = 𝑘𝑇 = 1/2𝑚𝑣 2
2
• Internal energy is the sum of
the KE of all atoms or:
3
3
ETh= 𝑈 = 𝑁𝑘𝑇 𝑜𝑟 𝑛𝑅𝑇
2
R = 8.31 J/mol·K
kB = 1.38 x 10 -23 J/K
2
The temperature of air in the upper
atmosphere is hot. could you get
burned from this?
KMT summary:
• Matter is made up of particles having negligible mass
are in constant random motion (vibrate, rotate,
translate)
• The particles are separated by great distances
• The particles collide perfectly elastically (there are no
forces acting except during the collision)
• The temperature of a substance is related to the
molecular velocity.
• Thermal energy is often transferred via a collision.
What are the two ways to add or
remove energy from a closed system?
(Ideal Gas)