Not so long ago, in a chemistry lab far far away…May the FORCE/area be with you

Gas Laws: IntroductionAt the conclusion of our time together, you should be able to:

1. List 5 properties of gases2. Identify the various parts of the kinetic

molecular theory3. Define pressure4. Convert pressure into 3 different units5. Define temperature6. Convert a temperature to Kelvin

Hittite Innovations:

Importance of Gases

Airbags fill with N2 gas in an accident.

Gas is generated by the decomposition of sodium azide, NaN3.

2 NaN3 ---> 2 Na + 3

N2

THREE STATES OF MATTER

General Properties of Gases

There is a lot of “free” space in a gas.

Gases can be expanded infinitely.

Gases fill containers uniformly and completely.

Gases diffuse and mix rapidly.

To Review

Gases expand to fill their containers

Gases are fluid – they flow Gases have low density

1/1000 the density of the equivalent liquid or solid

Gases are compressible Gases effuse and diffuse

Most Caring Person!!

An eye witness account from New York City on a cold day in December. Some years ago a little boy, about 10-years-old, was standing before a shoe store on the roadway, barefooted, peering through the window, and shivering with cold.A lady approached the young boy and said, "My, but you're in such deep thought staring in that window!“"I was asking God to give me a pair of shoes,“ was the boy's reply.

Most Caring Person!!The lady took him by the hand, went into the store, and asked the clerk to get half a dozen pairs of socks for the boy. She then asked if he could give her a basin of water and a towel. He quickly brought them to her.She took the little fellow to the back part of the store and, removing her gloves, knelt down, washed his little feet, and dried them with the towel. By this time, the clerk had returned with the socks. Placing a pair upon the boy's feet, she purchased him a pair of shoes.

Most Caring Person!!

She tied up the remaining pairs of socks and gave them to him. She patted him on the head and said, "No doubt, you will be more comfortable now.“As she turned to go, the astonished kid caught her by the hand, and looking up into her face, and with tears in his eyes, asked her.

"Are you God's wife?"

Properties of GasesGas properties can be

modeled using math. This model depends on —

V = volume of the gas (L) T = temperature (K)

› ALL temperatures in the entire unit MUST be in Kelvin!!! No Exceptions!

n = amount (moles) P = pressure

(atmospheres)

Ideal GasesIdeal gases are imaginary gases that perfectly fit all of the assumptions of the kinetic molecular theory. Gases consist of tiny particles that

are far apart relative to their size. Collisions between gas particles and between particles and the walls of the container are elastic collisions

No kinetic energy is lost in elastic collisions

Ideal Gases (continued)

Gas particles are in constant, rapid motion. They therefore possess kinetic energy, the energy of motion

There are no forces of attraction between gas particles

The average kinetic energy of gas particles

depends on temperature, not on the identity of the particle.

Bill Gates' RulesHere is a list of 11 things that many high

school and college graduates did not learn in school. In his book, Bill Gates talks about how feel-good, politically-

correct teachings created a full generation of kids with no concept of reality and how this concept has set them up for failure in the real world.

RULE 2 The world won't care about your self-esteem. The

world will expect you to accomplish something BEFORE you feel good about yourself.

Pressure

Is caused by the collisions of molecules with the walls of a container

Is equal to force/unit area SI units = Newton/meter2 = 1 Pascal (Pa) 1 atmosphere = 101,325 Pa 1 atmosphere = 1 atm = 760 mm Hg = 760

torr1 atm = 29.92 in Hg = 14.7 psi = 0.987 bar

= 10 m column of water.

Measuring Pressure

The first device for measuring atmospheric pressure was developed by Evangelista Torricelli during the 17th century.The device was called a “barometer”

  Baro = weight   Meter = measure

An Early Barometer

The normal pressure due to the atmosphere at sea level can support a column of mercury that is 760 mm high.

PressureColumn height measures

Pressure of atmosphere

1 standard atmosphere (atm) *

= 760 mm Hg (or torr) *= 29.92 inches Hg *= 14.7 pounds/in2 (psi)= 101.325 kPa

(SI unit is PASCAL)

= about 34 feet of water!

And now, we pause for this commercial message from STP

OK, so it’s really not THIS kind of STP…

STP in chemistry stands for Standard Temperature and Pressure

Standard Pressure = 1 atm (or an equivalent)

Standard Temperature = 0 deg C (273 K)

STP allows us to compare amounts of gases between

different pressures and temperatures

Let’s Review:Standard Temperature and

Pressure“STP”

P = 1 atmosphere, 760 torr T = 0°C, 273 Kelvins The molar volume of an ideal gas is 22.42 liters at STP

15 Helpful Hints On The Lab Report from

Mr. T’s Vast Lab Experience!!!

Hint #1. When you don't know what you are doing, do it neatly. 

Pressure Conversions

A. What is 475 mm Hg expressed in atm?

B. The pressure of a tire is measured as 29.4 psi.

What is this pressure in mm Hg? = 1.52 x 103 mm Hg

= 0.625 atm475 mm Hg x

29.4 psi x

1 atm760 mm Hg

760 mm Hg 14.7 psi

101.325 kPa 14.7 psi

Pressure Conversions – Your Turn

A. What is 2.00 atm expressed in torr?

B. The pressure of a tire is measured as 32.0 psi.

What is this pressure in kPa?

= 1520 torr2.00 atm x 760 torr 1 atm

= 221 kPa32.0 psi x

Converting Celsius to Kelvin

Gas law problems involving temperature require that the temperature be in KELVINS!

Kelvins = °C + 273

°C = Kelvins - 273

Gas Laws: IntroductionLet’s see if you can:

1. List 5 properties of gases2. Identify the various parts of the kinetic

molecular theory3. Define pressure4. Convert any kind of pressure to

atmospheres5. Define temperature6. Convert a temperature to Kelvin

Pass the Clicker!!!

Convert 190.0 mm Hg to kilopascals (1 atm = 101.325 kPa)

1. 2.5332. 25.333. 142.54. 14255. Not listed

Convert 3.1 atm to mm of Hg. (1 atm = 101.325 kPa)

1. 3102. 31003. 2404. 24005. Not listed

Convert 260oF to Celcius.

1. -1302. 5333. 0.954. -135. Not listed

The End!!!