5-_kinetic_molecular_theory

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Kinetic Molecular Theory and

the Gas Laws

Phases of Matter, Kinetic Molecular Theory,

and Temperature

Gas Laws

Phase Changes



Phases of Matter

There are four phases of matter:

1. Solid

2. Liquid

3. Gas

4. Plasma

The state of matter depends on the motion of the

molecules that make it up.



Solids

Solids are objects that have definite shapes andvolumes. The atoms or molecules are tightly

packed, so the solid keeps its shape. Thearrangement of particles in a solid are in a regular,repeating pattern called a crystal.

Microscopic picture of a solid.



Liquids

The particles in a liquid are close together, but are

able to move around more freely than in a solid.

Liquids have no definite shape and take on theshape of the container that they are in.

Microscopic picture of a

liquid.



Gases

A gas does not have a definite shape or volume. The

particles of a gas have much more energy than

either solids or liquids and can move aroundfreely.

Microscopic picture of a gas.



Plasma

Plasma is a gas-like mixture of positively and

negatively charged particles. Plasma is the most

commonly found element in the universe, makingup 99% of all matter. It is found in stars, such as

the sun, and in fluorescent lighting. Plasma occurs

when temperatures are high enough to cause

particles to collide violently and be ripped apartinto charged particles.



Kinetic Molecular Theory of Matter

All matter is made of particles that are inconstant motion. The more energy the

particles have, the more freely they movearound. This freedom that molecules haveis the determining factor for their state of matter. Therefore, solids have the least

amount of energy. Liquids come nextfollowed by gases. Finally, plasma has themost energy of any state of matter.



Temperature

Temperature is a measure of the amount of the

average kinetic energy of the particles in matter.

The more kinetic energy the particles have, thehigher the temperature. The temperature of

particles are usually recorded in one of three ways:

1. Fahrenheit (ºF)

2. Celsius (ºC)

3. Kelvin (K)Do you remember which is the standard unit????



Fahrenheit

Developed by Daniel Gabriel Fahrenheit, who is best

known for inventing the alcohol thermometer and

mercury thermometer in the early 1700¶s. It is basedon 32º for the freezing point of water and 212º for

the boiling point of water. The interval between the

freezing and boiling points are divided into 180 parts.

The conversion to Celsius is:

ºF = (9/5 ºC) + 32



Celsius

Scale developed by Anders Celsius in the early to

mid-1700¶s, working from the invention of

Fahrenheit's thermometers. The Celsius scale is based on 0º for the freezing point of water and

100º as the boiling point. The interval between the

freezing and boiling points are divided into 100

parts.The conversion to Fahrenheit is: ºC= (5/9)(ºF-32)

The conversion to Kelvin is: K=ºC +273



Kelvin

Developed by William Thompson Kelvin in 1848,

Kelvin is a temperature scale having an absolute

zero below which temperatures do not exist. At0K, all molecules cease any type of motion (as in

the temperature of outer space). It corresponds to a

temperature of -273° on the Celsius temperature

scale. The Kelvin degree is the same size as theCelsius degree, so the freezing point of water is at

273K and the boiling point is at 373K.

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The Behavior of Gases

The behavior of gases can be explained by the way

their particles interact with each other and the

environment around them.The particles are constantly colliding with one

another and other objects. Since the molecules

have mass, there is a certain amount of pressure

being applied.

As the volume of the gas and/or the temperature of

the gas change, so does its behavior.



Gas Laws

The result of a force distributed

over an area.SI unit for pressure = pascal (Pa) =

N/m2

(one kilopascal = kPa= 1000 Pa)



Factors that Affect Pressure of an

Enclosed Gas

Temperature

Volume Number of Particles



Temperature

Raising the temperature of a gas

will increase its pressure if thevolume of the gas and the number

of particles are constant



Volume

Reducing the volume of a gas

increase its pressure if thetemperature of the gas and the

number of particles are constant.



Number of Particles

Increasing the number of particles

will increase the pressure of a gasif the temperature and the volume

are constant.



Boyle¶s Law

Boyle¶s Law shows the relationship between thevolume and pressure of a gas:

The volume of a fixed amount of gas varies

inversely with the pressure on the gas.

If the pressure increases, the volume decreases; if the pressure decreases, then the volume increases.

P1V1=P2V2



Boyle¶s Law



A Graph of Boyle¶s Law



Charles¶s Law

Charles¶s Law shows the relationship between thetemperature and volume of a gas:

The volume of a fixed amount of gas varies

directly with the temperature of the gas.

If the temperature increases, the volume increases; if thetemperature decreases, then the volume decreases.

V1 = V2

T1 T2



A Graph of Charles¶s Law

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The Combined Gas Law

The relationships described by Boyle¶s law and Charles¶ law can be

described as a single law. The combined gas law describes the

relationship among the temperature, volume, and pressure of a gas when

the number of particles is constant.

2

22

1

11

T

V P

T

V P !



Phase Changes

A reversible physical change that occurs when asubstance changes from one state of matter to

another.The temperature of a substance doesn¶t changeduring a phase change.

Energy is either absorbed or released during a phase change.

Heat of fusion = energy a substance must absorbin order to change from a solid to a liquid.



Six Common Phase Changes

1. Melting- temperature at which a substance

changes from solid to liquid.

2. Freezing ± temperature at which a

substance changes from a liquid to a solid.

3. Evaporation ± substance changes from a

liquid to a gas. (Heat of Vaporization-energy a substance must absorb in order to

change from a liquid to a gas.)



4. Condensation- substance changes from a

gas or vapor to a liquid.

5. Sublimation ± substance changes from a

solid to a gas or vapor without changing to a

liquid first (endothermic)

6. Deposition ± substance changes directlyinto a solid without first changing to a

liquid (exothermic)

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