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Title: Kinetic%20Molecular%20Theory%20and%20the%20Gas%20Laws


1
Kinetic Molecular Theory and the Gas Laws
  • Phases of Matter, Kinetic Molecular Theory, and
    Temperature
  • Gas Laws
  • Phase Changes

2
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.

3
Solids
  • Solids are objects that have definite shapes and
    volumes. The atoms or molecules are tightly
    packed, so the solid keeps its shape. The
    arrangement of particles in a solid are in a
    regular, repeating pattern called a crystal.

Microscopic picture of a solid.
4
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 the shape of the container that they are in.

Microscopic picture of a liquid.
5
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 around
    freely.

Microscopic picture of a gas.
6
Plasma
  • Plasma is a gas-like mixture of positively and
    negatively charged particles. Plasma is the most
    commonly found element in the universe, making up
    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
    apart into charged particles.

7
Kinetic Molecular Theory of Matter
  • All matter is made of particles that are in
    constant motion. The more energy the particles
    have, the more freely they move around. This
    freedom that molecules have is the determining
    factor for their state of matter. Therefore,
    solids have the least amount of energy. Liquids
    come next followed by gases. Finally, plasma has
    the most energy of any state of matter.

8
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, the higher 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????

9
Fahrenheit
  • Developed by Daniel Gabriel Fahrenheit, who is
    best known for inventing the alcohol thermometer
    and mercury thermometer in the early 1700s. It
    is based on 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

10
Celsius
  • Scale developed by Anders Celsius in the early to
    mid-1700s, 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 KºC 273

11
Kelvin
  • Developed by William Thompson Kelvin in 1848,
    Kelvin is a temperature scale having an absolute
    zero below which temperatures do not exist. At
    0K, 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 the Celsius degree, so the freezing point
    of water is at 273K and the boiling point is at
    373K.

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12
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.

13
Gas Laws
  • The result of a force distributed over an area.
  • SI unit for pressure pascal (Pa) N/m2
  • (one kilopascal kPa 1000 Pa)

14
Factors that Affect Pressure of an Enclosed Gas
  • Temperature
  • Volume
  • Number of Particles

15
Temperature
  • Raising the temperature of a gas will increase
    its pressure if the volume of the gas and the
    number of particles are constant

16
Volume
  • Reducing the volume of a gas increase its
    pressure if the temperature of the gas and the
    number of particles are constant.

17
Number of Particles
  • Increasing the number of particles will increase
    the pressure of a gas if the temperature and the
    volume are constant.

18
Boyles Law
  • Boyles Law shows the relationship between the
    volume 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.
  • P1V1P2V2

19
Boyles Law
From Physical Science, Merrill, 1993
20
Boyles Law
21
A Graph of Boyles Law
22
Charless Law
  • Charless Law shows the relationship between the
    temperature 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 the temperature decreases, then the
    volume decreases.
  • V1 V2
  • T1 T2

23
A Graph of Charless Law
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24
The Combined Gas Law
  • The relationships described by Boyles 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.

25
Phase Changes
  • A reversible physical change that occurs when a
    substance changes from one state of matter to
    another.
  • The temperature of a substance doesnt change
    during a phase change.
  • Energy is either absorbed or released during a
    phase change.
  • Heat of fusion energy a substance must absorb
    in order to change from a solid to a liquid.

26
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.)

27
  • 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 directly into a
    solid without first changing to a liquid
    (exothermic)

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