Lesson 1: Basic Terminology This lesson reviews terms used to describe the properties and behavior...

Lesson 1: Basic Terminology

This lesson reviews terms used to describe the properties and behavior of gases.

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Opening thoughts…

Have you ever:

Seen a hot air balloon?

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Opening thoughts…

Have you ever:

Seen a hot air balloon?

Had a soda bottle spray all over you?

Baked (or eaten) a nice, fluffy cake?

These are all examples of gases at work!


Properties of Gases

You can predict the behavior of gases based on the following properties:


Pressure

Volume

Amount (moles)

Temperature

Lets review each of these briefly…


PressureVolume

Amount (moles)

Temperature


Pressure

Pressure is defined as the force the gas exerts on a given area of the container in which it is contained. The SI unit for pressure is the Pascal, Pa.

• If you’ve ever inflated a tire, you’ve probably made a pressure measurement in pounds (force) per square inch (area).


E. Pressure

Barometer measures atmospheric pressure

Mercury Barometer

Aneroid Barometer

E. Pressure Manometer

measures contained gas pressure

U-tube Manometer Bourdon-tube gauge


Pressure

VolumeAmount (moles)

Temperature


Volume

Volume is the three-dimensional space inside the container holding the gas. The SI unit for volume is the cubic meter, m3. A more common and convenient unit is the liter, L.

Think of a 2-liter bottle of soda to get an idea of how big a liter is. (OK, how big two of them are…)



Pressure

Volume

Amount (moles)Temperature


Amount (moles)

Amount of substance is tricky. As we’ve already learned, the SI unit for amount of substance is the mole, mol. Since we can’t count molecules, we can convert measured mass (in kg) to the number of moles, n, using the molecular or formula weight of the gas.

By definition, one mole of a substance contains approximately 6.022 x 1023 particles of the substance. You can understand why we use mass and moles!



Pressure

Volume

Amount (moles)

Temperature


Temperature

Temperature is the measurement of heat…or how fast the particles are moving. Gases, at room temperature, have a lower boiling point than things that are liquid or solid at the same temperature. Remember: Not all substance freeze, melt or evaporate at the same temperature.


Water will freeze at zero degrees Celsius. However Alcohol will not freeze at this temperature.

How do they all relate?

Some relationships of gases may be easy to predict. Some are more subtle.Now that we understand the factors that affect the behavior of gases, we will study how those factors interact.


How do they all relate?

Some relationships of gases may be easy to predict. Some are more subtle.Now that we understand the factors that affect the behavior of gases, we will study how those factors interact.

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Let’s go!

A. Kinetic Molecular TheoryA. Kinetic Molecular Theory

Particles in an ideal gas… have no volume. have elastic collisions. are in constant, random, straight-line

motion. don’t attract or repel each other. have an avg. KE directly related to Kelvin

temperature.

B. Real GasesB. Real Gases

Particles in a REAL gas… have their own volume attract each other

Gas behavior is most ideal… at low pressures at high temperatures in nonpolar atoms/molecules

C. Characteristics of GasesC. Characteristics of Gases Gases expand to fill any container.

random motion, no attraction

Gases are fluids (like liquids). no attraction

Gases have very low densities. no volume = lots of empty space

C. Characteristics of GasesC. Characteristics of Gases

Gases can be compressed. no volume = lots of empty space

Gases undergo diffusion & effusion. random motion

E. Pressure

2m

NkPa

KEY UNITS AT SEA LEVEL

101.325 kPa (kilopascal)

1 atm

760 mm Hg

760 torr

14.7 psi

F. STP

Standard Temperature & PressureStandard Temperature & Pressure

0°C0°C 273 K273 K

1 atm1 atm 101.325 kPa101.325 kPa-OR--OR-

STP

Lesson 2: Boyle’s Law

This lesson introduces Boyle’s Law, which describes the relationship between pressure and volume of gases.

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Boyle’s Law

This law is named for Charles Boyle, who studied the relationship between pressure, p, and volume, V, in the mid-1600s.

Boyle determined that for the same amount of a gas at constant temperature, results in an inverse relationship:when one goes up, the other comes down.


pressure

volume

What does Boyle’s Law mean?

Suppose you have a cylinder with a piston in the top so you can change the volume. The cylinder has a gauge to measure pressure, is contained so the amount of gas is constant, and can be maintained at a constant temperature.

A decrease in volume will result in increased pressure.

Hard to picture? Let’s fix that!


Boyle’s Law at Work…

Doubling the pressure reduces the volume by half. Conversely, when the volume doubles, the pressure decreases by half.


Lesson 2 Complete!

This concludes Lesson 2 on Boyle’s Law!

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Click the Main Menu button below, then select Lesson 3 to learn about how temperature fits in.

Lesson 3: Charles’ Law

This lesson introduces Charles’ Law, which describes the relationship between volume and temperature of gases.

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Charles’ Law This law is named for Jacques Charles, who

studied the relationship volume, V, and temperature, T, around the turn of the 19th century.

This defines a direct relationship: With the same amount of gas he found that as the volume increases the temperature also increases. If the temperature decreases than the volume also decreases.


volume

temperature

What does Charles’ Law mean?Suppose you have that same cylinder with a piston in the top allowing volume to change, and a heating/cooling element allowing for changing temperature. The force on the piston head is constant to maintain pressure, and the cylinder is contained so the amount of gas is constant.

An increase in temperature results in increased volume.

Hard to picture? Let’s fix it (again)!


Charles’ Law at Work…

As the temperature increases, the volume increases. Conversely, when the temperature decreases, volume decreases.


Lesson 3 Complete!

This concludes Lesson 3 on Charles’ Law!

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Click the Main Menu button below, then select Lesson 4 to put all the pieces together with the Ideal Gas Law.

Mission complete!

You have completed the lessons and review. Congratulations!

You should now have a better understanding of the properties of gases, how they interrelate, and how to use them to predict gas behavior.

Please click on the button below to reset the lesson for the next student. Thanks!

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Lesson 1: Basic Terminology This lesson reviews terms used to describe the properties and behavior...

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