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# Physical Science - 3.2

The Gas Laws
by

## Sarah Gleason

on 19 September 2013

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#### Transcript of Physical Science - 3.2

Chapter 3.2
The Gas Laws
Charles's Law
Combined Gas Law
Changes in volume, temperature, pressure and the number of particles have PREDICTABLE effects on the behavior of a gas.
Pressure
The results of a force distributed over an area
Describes relationship of the temperature and volume of a gas
Combines Charles's and Boyle's laws
Measured in pascals (Pa) - shorthand for newtons per square meter
1 pascal is a small amount of pressure so scientist use kilopascals

Pressure
Pressure can occur with any sized material - even atoms!
Collisions occur between particles of a gas and the walls of a closed container (like a balloon) and cause PRESSURE
The more frequent the collisions, the greater the pressure of the gas is
Factors that Affect Gas Pressure
Temperature - speeds up/ slows down particles
Volume - like changing the container a gas is in
Number of Particles - like adding or removing a certain amount of the gas
Temperature (and gases)
As temperature rises, the average kinetic speed of the particles in a gas INCREASE and there are more collisions - greater pressure
As the temperature lowers, the average kinetic speed of particles DECREASES, leading to less collisions - lower pressure
**Only if the volume and number of particles are constant (stay the same)
Volume
If you reduce (lower) the amount of volume of a gas - the gas is now trapped in a smaller space, and has more collisions and a HIGHER pressure
If you increase the amount of volume or space of a gas - the gas particles have more room to move around - less collisions and LOWER pressure
** ONLY if the temperature and number of particles remain constant (stay the same)
Number of (gas) Particles
If you add more particles (more gas) pressure will INCREASE
more particles = more collisions
If you take away particles (remove gas) the pressure will DECREASE
less particles = less collisions
** Only if the temperature and volume are constant (remain the same)
** Named after French physicist Jacques Charles
Absolute Zero
This is the idea that Charles used to state the relationship between temperature and volume
Absolute zero is equal to 0 k (kelvin)
This is a theoretical temperature because no scientist has currently been able to produce it
As a gas reaches this temperature it would change to a liquid or a solid
Charles's Law
States the the volume of a gas is directly proportional to its temperature (in kelvins) - if the pressure and amount of particles stay the same
V1 = Initial Volume
T1 = Initial Temperature
V2 = Final Volume
T2 = Final Temperature
** Temperature MUST be in Kelvin
How to Convert to Kelvin?
That's all, just remember to CONVERT!!
Boyle's Law
Named after Robert Boyle - who was the first to describe the relationship between pressure and the volume of a gas
Boyle's Law
States that the volume of a gas is inversely proportional to the pressure if the temperature and number of particles are constant
P1 = Initial (starting) pressure
V1 = Initial (starting) volume
P2 = Final (after the change) pressure
V2 = Final (after the change) volume
If volume increases SO DOES the temperature
If the volume increases - temperature decreases (opposites)
Describes the relationship among temperature, volume and pressure
**When the number of particles are constant

P1 = Starting Pressure
V1 = Starting Volume
T1 = Starting Temperature
P2 = Final Pressure
V2 = Final Volume
T2 = Final Temperature
Why Scientist use the Combined Gas Law?
It is much harder for scientist to control all factors in natural settings (like temp, and pressure, and volume)
So combined gas law accounts for this and allows scientist to deal with changing factors
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