Heating/Cooling Curve and Gas Laws Unit 9 and some of 8

Ideal Gas Postulates

1) the volume of gas particles is so small compared to the distance between them that the volume is assumed to be negligible

2) gas particles exhibit NO INTERMOLECULAR INTERACTION with their surrouding or other gas molecules/particles

3) gas particles are in constant, random, rapid straight lines of motion, colliding with eachother and the sides of the container

4) gas particles have elastic collisions with eachother and the walls of the container (conservation of energy)

What does each ideal gas postulate contradict

Negligible volume = matter has mass, its small but there

No IMFS = All molecules are some type of weak London dispersion

Constant, random, straight line movement = gravity and magnetism can cause predicted and bent movement

Total elastic collisions = a small amount of energy is lost with collision

Ideal Gases

Real gases behave most like ideal gases under high temperatures and low pressure

Pressure of gas

Measuring the collisions of gas particles within a container

elastic collisions

A collision in which no kinetic energy is lost; gas particles have same speed before and after the collision

(Ideal gas postulate)

What is the relationship between temperature and volume

Linear

As temperature decreases, volume decreases

As volume increases, temperature increases

V1/T1=V2/T2 (both go up or both go down)

Always use KELVIN!

Before doing any equations you must..

Convert to kelvin and make sure the units are the same (both atp or both kPa)

Charles law: Volume temperature relationship

At constant pressure, as temperature increases volume will increase

Can volume be negative (absolute zero)

NO NEVER! This is because we never know the particles exact location and/or movement

Thus, we MUST use kelvin because Celsius will give us 0

Ideal gases and temperature

When solving for the temperature of an ideal gas, the temp must always be in kelvin

Pressure

Force applied to an object by another object

Pressure = force/area

Units= atmospheres (kPa) or kilopascals (kPa)

1 atm=101.3kPa

Boyle law: pressure and volume

At constant temp. As pressure increases the volume will decrease and vice versa.

What's the relationship between pressure and volume?

As pressure decreases, volume increases

This is because: air inside can expand with less pressure and take up more volume ex: balloon

Note: THIS IS AN EXPONENTIAL RELATIONSHIP meaning it's a more sloped relationship if graphed and not a straight line

VOLUME AND PRESSURE NEVER READH ZERO

P1xV1 = P2xV2

Combined Gas Law

(P1xV2)/T1 = (P2xV2)/T2

(IN PERIODIC TABLE)

Constant Pressure, Constant Temp, Constant Volume, and No Constant name of law and equation

Constant pressure = Charles Law

V1/T1 = V2/T2

Constant temperature = Boyles Law

P1xV1=P2xV2

Constant volume = Gay-Lussacs Law

P1/T1 = P2/T2

No constants = Combined gas law

(P1xV1)/T1 = (P2V2)/T2

Avogadros Law

At constant temperature

V1/n1 = V2/n2

At standard STP (temp and pressure) the volume of a gas is directly related to the number of particles in the container

The volume the moles occupies does not differ between substances.

1mole = 22.4L (IDEAL gas)

How much volume does one mole take up

22.4L

What is pressure

force exerted per unit area ( collisions! ) more collisions = higher pressure

When does the number of gas molecules/particles change?

ONLY if gas is added or removed

Kinetic Molecular Theory

Constant random motion:

Gas particles are in constant, random motion, moving in straight lines until they collide with other particles or the container walls.

Negligible particle volume:

The combined volume of the gas particles is negligible compared to the volume of the container they occupy.

No intermolecular forces:

Gas particles exert no attractive or repulsive forces on one another except during collisions.

Elastic collisions:

Collisions between gas particles and the container walls are perfectly elastic, meaning no kinetic energy is lost during collisions.

Average kinetic energy proportional to temperature:

The average kinetic energy of the gas particles is directly proportional to the absolute temperature of the gas.

What conditions are needed for the same number of particles?

Same volume, pressure, temp (Avogadro)

Under which conditions of pressure and temp is a real gas like an ideal gas

Low pressure and high temp

Or small particles/radius

VOLUME AND MOLES ARE DIRECTLY RELATED