Quick Video Recap?

Take a moment to watch this video to help you learn or think about the information in this presentation!

Watch this video about Kinetic Molecular Theory

• Use kinetic molecular theory to connect particle-level and macroscopic behavior

Do we need to add anything?

​

Phases of Matter

(or states)

The optimist sees the glass half full.

The pessimist sees the glass half empty.

The chemist see the glass completely full,

half in the liquid state and half in the vapor state.

Water is an amazing substance.

Earth is the only place in the universe that we know of that has the right conditions for water to exist as solid, liquid, and gas in the same place at the same time.

Move the red dot over solid water, yellow square over liquid water, green triangle over gaseous water in the picture.

Water is an amazing substance.

Earth is the only place in the universe that we know of that has the right conditions for water to exist as solid, liquid, and gas in the same place at the same time.

H₂O gas

H₂O solid

H₂O liquid

💨

Particulates Representing

States of Matter

The boxes below represent particulate diagrams of the three states of matter.

Drag the cardinal square over solid,

Drag the purple dot over liquid,

Drag the navy triangle over gas

These are side views of the containers.

What is a gas?

Demos!

Attempting to prove gases exist

• Do gases even exist?
• Capturing a gas

​

cup and tank

Time to blow something up!

P vs n

What happens to the pressure when more moles are added to the container?

There is gas in the flask, and more gas is added with the syringe. What would the pressure gauge read in the second picture? (volume and temp remain constant)

P vs n

??

There is gas in the flask, and more gas is added with the syringe. What would the pressure gauge read in the second picture? (volume and temp remain constant)

P vs n

More particles present will hit the sides of the container more often causing greater pressure.

Which graph below best represent the relationship between amount of gas (n) and volume (V) of container?

(holding pressure and temperature constant.)

Which graph below best represent the relationship between moles of gas and volume of container? (holding pressure and temperature constant.)

number of molecules and volume

• number of particles and volume
• V vs n
• increase the number of particles, (while pressure & temp remain constant) and the volume will increase.
• This is a direct relationship
• n is proportional to V

The pressure of the red gas would be ______ the pressure of the blue gas.�(holding volume and temperature constant)

1. (red) higher than (blue)
2. (red) lower than (blue)
3. (red) is the same as (blue)

The pressure of the red gas would be ______ the pressure of the blue gas.�(holding volume and temperature constant)

1. (red) higher than (blue)
2. (red) lower than (blue)
3. (red) is the same as (blue)
1. As counterintuitive as this may seem, the size and mass of the gas particles do not affect the pressure, only the number of particles affect the pressure. Because the gas particles are SO far apart, their personal size is insignificant and each gas particle no matter what size causes the same pressure.

Remember:

• Assuming the blue atoms are lighter in mass than the red molecules,
• the average speed of the blue atoms will be faster than the average speed of the red molecules, but the heavier molecules hit with more heft,
• resulting in the same kinetic energy,
• and ultimately causing the same pressure.

Same Temp

Same Volume

Pourable Fire Extinguisher

Characteristics of Gases

• Physical properties of gases are all similar.
• Composed mainly of nonmetallic elements with simple formulas and low molar masses.
• Unlike liquids and solids, gases
• expand to fill their containers.
• are highly compressible.
• have extremely low densities.
• Two or more gases form a homogeneous mixture.

Some Common Gases

Table 10.1 Some Common Compounds That Are Gases at Room Temperature

How do we describe gas behavior?

Kinetic Molecular Theory

KMT - Kinetic Molecular Theory

1. KMT assumes collisions that are elastic, momentum is conserved (more on that in physics).
2. KMT is dependent upon a gas behaving as if the gas particles have NO IMFs.
3. KMT also considers gases to be “point masses.” That is to say, the size of each atom is insignificant.
4. The temperature of a gas is proportional to its kinetic energy.
5. The absolute kinetic energy of the molecules is proportional to the absolute temperature. At the same temperature, molecules of all gases have the same average kinetic energy

KMT Implies

If two molecules are at the same temperature they contain the same average kinetic energy. If they are the same type of molecule (same mass) they have the same average speeds. If they are different types of molecules (different masses), they will have different average speeds.

What properties of a gas can we measure?

Properties that define the state of a gas sample

1. Temperature
2. Volume
3. Pressure
4. Number of gas particles, usually expressed as number of moles

Molecular Property

Observable Property

Connecting Observations and Molecular Properties

Temperature

Speed of gas particles

Pressure

Volume

Moles

3D space in which the gas is confined

Collisions of gas particles with the container

Number of of gas particles

Ways to measure Gas Concentration

• Density - g/mL or g/cm³

​

• Mole Fraction - X_n =

​

Association Statements

direct and inverse

• Direct Association (both variables move in same direction)
• Work less hours produces less pay.
• Students that use more active study achieve greater success.
• Inverse Association (both variables move in opposite direction)
• Brush teeth more means less cavities.
• Students who study less are more stressed on exam day.

Hot bath

When the flask was placed in hot water - the particles started moving faster.

The number of collisions between particles increased.

Since my container is allowed to change size, the increased collisions caused a change in the space.

This appeared to be the balloon increasing in size.

Cold bath

When the flask was placed in cold water - the particles started moving slower.

The number of collisions between particles decreased.

Since my container is allowed to change size, the decreased collisions caused a change in the space.

This appeared to be the balloon decreasing in size.

Let’s take this to the lab!

Lab #18: The relationship between Temperature and Volume

Data from Mrs. Weeks

July 14, 2020

Volume and Temperature have a…

Direct Relationship

One goes up & the other goes up

Implies there is a “lowest” temperature

If we extend the x axis…

We get a graph like:

Why not just move the Y axis to meet up with the 0 mark?

Now we need a new temperature scale…

Early thermometers…

Mariani - Mariani's excellent glass-blowing skills, his Florentine thermometers produced the same temperature readings with regularity.

The Florentine thermometer was also a sealed liquid-in-glass design (Image 1). In this instance, the expansion and contraction of the thermometer's liquid was measured against a scale of glass beads that marked the neck of the phial. A variety of liquids were used to measure temperature, but most thermometers were filled with water or spirit of wine. This was a colourless spirit, as red dye tended to soil the tube.

Andrea Mariani, master glass-blower to Ferdinand II, Grand Duke of Tuscany, produced many of the thermometers used at the Accademia del Cimento (the Academy of Experiments), which was founded by Ferdinand II in 1657 to conduct extensive experiments on the conditions of the atmosphere. He claimed his workshop could produce 50 degree thermometers with uniformity; however, manufacturing consistent products measuring 100 and 300 degrees proved too challenging.

Although Florentine scales did not use fixed points, such as the heat of boiling water, to establish the amount of spirit sealed inside the tube, thermometers produced in Mariani's workshop are remarkable in that their temperature readings consistently agree between each other.

Taken from here - click through to learn more about early thermometers!

Temperature Scales

Anders Celsius

• References boiling point of pure water as 100
• References freezing point of pure water as 0

​

​

Daniel Fahrenheit

• References human body temperature for 100
• References either the coldest temp he could stand or possibly the freezing point of salt-water (?) as 0

​

​

Temperature Scales

Fahrenheit

Celsius

Kelvin

​

MUST use K temperatures in this class

Quick Reminder about Temperature

On your Cheat Sheet

Solve for K in terms of F

Quick Reminder about Temperature

On your Cheat Sheet

Solve for K in terms of F

K = +273.15

Analysis Questions

7. Based on your analysis, why is it theoretically impossible to have a temperature lower than absolute zero?

​

8. What are the weaknesses in this method of calculating absolute zero?

9. How could the experiment be improved to yield more accurate results?

10. How do you think the original scientists (in the late 1800’s) managed to get such an accurate answer?

What “natural laws” do we discover when we measure gases?

Expressing direct and inverse relationships mathematically

• direct relationship is a quotient
• between hours worked and $$ earned
• inverse relationship is a product
• between # of kids at the party and the size of each portion of cake

birthday cake = # kids at party x size of portion of cake

Charles’ Law

The volume of a fixed amount of gas at constant pressure is directly proportional to its absolute temperature.

constant

Charles’ Law example

A gas occupies 2.7 L at 28^oC. If the temperature is raised to 97^oC at constant pressure, what volume will the gas occupy?

​

Charles’ Law example

A gas occupies 2.7 L at 28^oC. If the temperature is raised to 97^oC at constant pressure, what volume will the gas occupy?

​

V₂ = V₁T₂ V₂ = (2.7L) ((273.15+97) K)

T₁ ((273.15+28) K)

​

V₂ = 3.3 L

2) Rearrange

3) Plug and chug

Carol solved the following problem incorrectly, can you find her error?

A gas in a 2 L container has an initial temperature of 298 K. After going through a cold spell, the container’s volume decreased to 1.5 L. What was the new temperature of the gas?

2 L = 1.5 L

298 k xK

X = 0.0100 K

Carol solved the following problem incorrectly, can you find her error?

A gas in a 2 L container has an initial temperature of 298 K. After going through a cold spell, the container’s volume decreased to 1.5 L. What was the new temperature of the gas?

2 L = 1.5 L

298 k xK

X = 0.0100 K -- she solved for 1/x and not x

Watch out for this one!

Reindeer

Air goes from -40 ^oC to 38 ^oC in a breath. How much does a 6.0 L breath expand?

Prep for the quiz…?

Ask any questions about KMT

Turn in Lab #18

Now you can:

Quiz Time!

You must show work clearly in the space to support you answer.

No work = no credit.

Box your final answer with units and descriptors.

The Priestley Riots

https://en.wikipedia.org/wiki/Priestley_Riots