IT’S A GAS…IT’S A GAS…

Gases have some interesting characteristics that have fascinated scientists for 300 years.

The first gas to be studied was airair & it was a long time before it was discovered that air was actually a mixture of particles rather than a single gassingle gas.

Although air is a mixture of several different gases, it behaves much the same as any single gas.

Gases have some interesting characteristics that have fascinated scientists for 300 years.

The first gas to be studied was airair & it was a long time before it was discovered that air was actually a mixture of particles rather than a single gassingle gas.

Although air is a mixture of several different gases, it behaves much the same as any single gas.

The Nature of GasesThe Nature of Gases

Kinetic Molecular TheoryKinetic Molecular TheoryThe Kinetic Molecular Theory of Matter. Is used to explain the behaviors and characteristics of ideal gases

The theory states that the tiny particles in all forms of matter are in constant motionconstant motion.

There are 55 basic assumptions of the KMT as it applies to ideal gases.•Ideal gases are “perfect” gases that are used as a model to describe characteristics of real gases.

The Kinetic Molecular Theory of Matter. Is used to explain the behaviors and characteristics of ideal gases

The theory states that the tiny particles in all forms of matter are in constant motionconstant motion.

There are 55 basic assumptions of the KMT as it applies to ideal gases.•Ideal gases are “perfect” gases that are used as a model to describe characteristics of real gases.

KMT Assumption #1KMT Assumption #1A gas is composed of small hardsmall hard particles.

The particles have an insignificant volume and are relatively far

apart from one another.

There is empty spaceempty space between particles.

A gas is composed of small hardsmall hard particles.

The particles have an insignificant volume and are relatively far

apart from one another.

There is empty spaceempty space between particles.

All collisions a gas particle undergoes are perfectly elasticperfectly elastic.They exert a pressure but don’t lose any energy during the collisions.

All collisions a gas particle undergoes are perfectly elasticperfectly elastic.They exert a pressure but don’t lose any energy during the collisions.

KMT Assumption #2KMT Assumption #2

The particles in a gas move in constant random motion.constant random motion.Particles move in straight paths and are completely independent of each of otherParticles path is only changed by collidingcolliding with another particle or the sides of its container.

The particles in a gas move in constant random motion.constant random motion.Particles move in straight paths and are completely independent of each of otherParticles path is only changed by collidingcolliding with another particle or the sides of its container.

KMT Assumption #3 & #4KMT Assumption #3 & #4

No No attractive or repulsive forces between particles.

All gas particles at the same temperature have the same kinetic energy

K.E. = ½ (mass) (velocity)2

The speed of a molecule is Directly related to its Kelvin Temperature

All gas particles at the same temperature have the same kinetic energy

K.E. = ½ (mass) (velocity)2

The speed of a molecule is Directly related to its Kelvin Temperature

KMT Assumption #5KMT Assumption #5

Regardless of their chemical identity, gases tend to exhibit similar physical behaviorsphysical behaviors

Gas particles can be monatomic (Ne), diatomic (N2), or polyatomic (CH4) – but they all have some common properties:

Regardless of their chemical identity, gases tend to exhibit similar physical behaviorsphysical behaviors

Gas particles can be monatomic (Ne), diatomic (N2), or polyatomic (CH4) – but they all have some common properties:

The Nature of GasesThe Nature of Gases

Common Properties of all gasses. Common Properties of all gasses.

The Nature of GasesThe Nature of Gases

1. Gases have a small mass but can take a large volume. (Low Density)

2. Gases can be squeezed together.(Compressibility)

3. Gases fill their containers. (Expansion)

4. Gases diffuse. (Diffsion & Effusion)5. Gases flow easily and without

resistance throughout their container. (Fluidity)

1. Gases have a small mass but can take a large volume. (Low Density)

2. Gases can be squeezed together.(Compressibility)

3. Gases fill their containers. (Expansion)

4. Gases diffuse. (Diffsion & Effusion)5. Gases flow easily and without

resistance throughout their container. (Fluidity)

Gases have mass.Gases have mass.

Gases “R” squeezable Gases “R” squeezable

If you squeezesqueeze any gas, its volume can be reduced considerably

Gases have a low densitylow density which allows for a lot of empty empty spacespace between gas molecules.

If you squeezesqueeze any gas, its volume can be reduced considerably

Gases have a low densitylow density which allows for a lot of empty empty spacespace between gas molecules.

Gases fill their containersGases fill their containersGases expandexpand until they take up as much room as they possibly can.Gases spread out to fill containers until the concentration of gases is uniformuniform throughout the entire space.This is why that no- where around you is there an absence of air.

Gases expandexpand until they take up as much room as they possibly can.Gases spread out to fill containers until the concentration of gases is uniformuniform throughout the entire space.This is why that no- where around you is there an absence of air.

Gases diffuseGases diffuse

Gases can move through each other rapidly.

The movement of one substance through another is called diffusion.diffusion.

Because of all of the empty space between gas molecules, another gas molecule can pass between them until each gas is spread out over the entire container, the gases mix uniformly.

Gases can move through each other rapidly.

The movement of one substance through another is called diffusion.diffusion.

Because of all of the empty space between gas molecules, another gas molecule can pass between them until each gas is spread out over the entire container, the gases mix uniformly.

Gases flow past other gases!

Gases flow past other gases!

If I opened up a bag of popcorn in front of the class you would soon be able to smell it in the back.

The popcorn smell easily diffuses throughout the other gas molecules in the room.

If I opened up a bag of popcorn in front of the class you would soon be able to smell it in the back.

The popcorn smell easily diffuses throughout the other gas molecules in the room.

Diffusion or EffusionDiffusion or Effusion

When gas molecules randomly When gas molecules randomly move about a room it is called move about a room it is called

diffusion.diffusion.When gas molecules pass When gas molecules pass

through a tiny opening it is called through a tiny opening it is called effusion.effusion.

Some gases diffuse more rapidly then other gases based on their size and their energy.

The heavier and colder the gas the slower it moves.

When gas molecules randomly When gas molecules randomly move about a room it is called move about a room it is called

diffusion.diffusion.When gas molecules pass When gas molecules pass

through a tiny opening it is called through a tiny opening it is called effusion.effusion.

Some gases diffuse more rapidly then other gases based on their size and their energy.

The heavier and colder the gas the slower it moves.

Real Gases act like IDEAL gasses at high Temperatures and Low

Pressures.

We live at relatively high temperatures and Low pressures.

Real Gases differ from Ideal gases in that real gas molecules have

mass and they have intermolecular forces effecting the

molecules themselves.

Real Gases act like IDEAL gasses at high Temperatures and Low

Pressures.

We live at relatively high temperatures and Low pressures.

Real Gases differ from Ideal gases in that real gas molecules have

mass and they have intermolecular forces effecting the

molecules themselves.

REAL Gases are almost IDEAL.

REAL Gases are almost IDEAL.

A Real Gas can change its State

A Real Gas can change its State

• That empty space can be compressed by pressure allowing gas particles less room to move around thus decreasing the volume while increasing the Density.

• But be careful to much pressure can change a gas into a _________!

• That empty space can be compressed by pressure allowing gas particles less room to move around thus decreasing the volume while increasing the Density.

• But be careful to much pressure can change a gas into a _________!

LIQUIDLIQUID

This is how your shocks an struts work

in your car.

Gas variablesGas variablesExperimental work in chemistry requires the measurement of such quantities as volume, temperature, pressure, and the amount of sample.

In order to describe a gas sample completely and then make predictions about its behavior under changed conditions, it is important to deal with the values of:

Experimental work in chemistry requires the measurement of such quantities as volume, temperature, pressure, and the amount of sample.

In order to describe a gas sample completely and then make predictions about its behavior under changed conditions, it is important to deal with the values of:

1) amount of the gas (# of moles)

1) amount of the gas (# of moles) 2) volume 2) volume

3) temperature 3) temperature 4) pressure 4) pressure