KINETIC-MOLECULAR-THEORY-PPT............

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KINETIC MOLECULAR
THEORY
HOW GASES BEHAVE

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Postulates of KMT:
 Gases are composed of a many particles
that behav hard spherical objects in a state
of constant, random motion.
 These particles move in a straight line until
they collide with another particle or the
walls of the container.
 These particles are much smaller than the
distance between particles, therefore the
volume of a gas is mostly empty space and
the volume of the gas molecule themselves
is negligible.

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Postulates of KMT:
 There is no force of attraction between gas particles or
between the particles and the walls of the container.
 Collisions between gas particles or collisions with the
walls of the container are elastic. That is, none of the
energy of the gas particle is lost in a collision. The
average kinetic energy of a collection of gas particles is
dependent only upon the temperature of the gas.
 The average kinetic energy of a collection of gas
particles depends on the temperature of the gas and
nothing else.

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Kinetic Energy
• The energy of motion
• Directly proportional to the mass of the object and to
square of its velocity
FORMULA:

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Introduction to Energy
Types and Forms

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ENERGY AND ITS DIFFERENT FORMS
ENERGY
Energy exists in many forms.
Energy can be moved from one object to another.
Energy can be changed from one form to another.
Energy cannot be created or destroyed.

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Energy in two Forms
Potential Energy
Kinetic Energy
The energy in matter due to its position
or the arrangement of its parts
One of the most common equations for
potential energy can be used to determine
the energy of an object with respect to its
height above a base: PE = mgh ( Joule)
Potential Energy
Potential Energy has 4 forms:
1.Chemical energy
2.Nuclear energy
3.Gravitational energy
4.Elastic energy

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Potential Energy
1.Chemical energy - Energy released by a chemical
reaction
The food you eat contains chemical energy that is
released when you digest your meal. Wood, coal,
gasoline, and natural gas are fuels that contain
chemical energy
2. Nuclear energy - Energy contained in the nucleus of
an atom. Nuclear energy is released when nuclei are
split apart into several pieces, or when they are
combined to form a single, larger nucleus

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Potential Energy
3. Gravitational energy - The energy an object
or substance has because of its position;
anything “up high
4. Elastic energy - Energy stored in an object
by the application of force.
Must push or pull on an object

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The energy of a moving object
A common formula for kinetic
energy is for a moving mass: KE =
1/2 mv2
(Joule)
Kinetic Energy
Kinetic Energy has 5 forms:
1.Mechanical energy
2.Electrical energy
3.Thermal energy
4.Radiant energy
5.Sound energy

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Kinetic Energy
Mechanical energy
 Energy that moves objects from place to place
 You use mechanical energy when you kick a ball
or turn the pedals of a bicycle
 Other examples include water flowing in a stream,
tires rolling down a road
Electrical energy
 Energy that comes from the electrons within
atoms
 It can be generated at a power plant or inside a
battery and can power everything from remote-
controlled cars to refrigerators
 Lightning and static electricity are also forms of
electrical energy

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Kinetic Energy
Thermal energy - Internal energy of a
substance due to the vibration of atoms and
molecules making up the substance
Radiant energy -
Electromagnetic energy that travels in transverse
waves
 Energy that can move through empty space
 The sun and stars are powerful sources of
radiant energy
 The light given off by light bulbs and campfires
are also forms of radiant energy

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Kinetic Energy
Sound energy - Movement of energy
through substances in the form of
longitudinal
(compression) waves

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Law of Conservation of Energy
While energy can change forms, it is conserved. In other words, the total energy of
a system is a constant value. This is often written in terms of kinetic (KE) and
potential energy (PE):
KE + PE = Constant
With every transformation, some energy is converted to less useful forms. Energy
conversions are not 100% efficient. The energy output for the intended purpose is
seldom the same as the energy we put in.
100 J electricity in
95 J heat out
5 J light out

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Understand the
relationship between
energy, work, heat and
Internal Energy and Its
Changes

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Energy, Work, and Heat
ENERGY- is the capacity to do
work or transfer heat.
TYPES:
Kinetic Energy- Energy of
motion (e.g., a moving object).
Potential Energy- Energy stored
due to position or configuration
(e.g., a compressed spring).
Internal Energy- Total
microscopic energy
within a system,
including the energy of
molecular motion and
interactions.
• Energy can neither be
created nor destroyed
(First Law of
Thermodynamics), but
it can change forms.

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Work- is the transfer of energy due to a force
acting over a distance.
Formula: W=F d Unit: Joules(J)
⋅
F: Force (N)
d: Distance (m)
Heat- is the transfer of energy due to a
temperature difference between a system and
its surroundings.

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Characteristics:
Heat flows from a hotter object to a cooler one
until thermal equilibrium is reached.
• Heat transfer does not involve bulk motion
of the system (unlike work).
Relationship Between Energy, Work, and Heat
The change in internal energy (ΔU)
• The relationship is governed by the First Law of
Thermodynamics:

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Where:
ΔU: Change in internal energy.
Q: Heat added to the system
+ve when absorbed
• −𝑣𝑒 when released
W: Work done by the system
+ve when the system does work,
• −ve when work is done on the system).

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Example 1:
Problem:
A gas absorbs 500J of heat while performing
200J of work on its surroundings. What is the
change in the internal energy of the gas?
Formula:
ΔU=Q−W
Substitute the given values:
Δ =500 −200
𝑈 𝐽 𝐽
Calculate:
Δ =300
𝑈 𝐽

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Example 2:
A gas releases 600J of heat while 150J of
work is done on the gas. What is the change
in the internal energy of the gas?
Formula:
ΔU=Q−W
Substitute the given values:
ΔU=−600J−(−150J)
Simplify:
Δ =−600 +150 =−450
𝑈 𝐽 𝐽

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EXERCISE:
1. A gas absorbs 300J of heat and performs 100J
of work. Calculate the change in its internal
energy.
2. A gas releases 800J of heat while 200J of work
is done on the gas. Find the change in its
internal energy.
3. A gas absorbs 1,200J of heat and 400J of work
is done on the gas. Determine the change in its
internal energy.

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BASIC CALORIMETRY

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Calorimetry
Calorimetry is the science of measuring the amount of heat
transferred to or from a system during a chemical reaction,
physical change, or process. It is used to determine:
•Heat absorbed or released (Q).
•Specific heat capacity of substances.
•Enthalpy changes in reactions (e.g., combustion, melting)
-Calorimetry experiments are conducted using a calorimeter,
a device designed to minimize heat exchange with the
surroundings.

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Calorimetry
Heat Transfer Formula:
Where:
Q: Heat transferred (in joules, ).
𝐽
m: Mass of the substance (in kilograms or grams).
c: Specific heat capacity (in / )
𝐽 𝑔∘𝐶
-heat capacity of water: 4.18 /
𝐽 𝑔∘𝐶
ΔT: Temperature change ( final− initial)
𝑇 𝑇

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EXAMPLE:

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EXAMPLE:

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Calorimetry : EXERCISE
1.
A 150 g cream mixture has its temperature increased
from 5°C to 25°C. If the specific heat capacity of the
mixture is 3.9 J/(g C), how much heat is required?
∘
2.
A 2 kg aluminum rod (specific heat capacity 0.9 J/(g C)
∘
is cooled from 80°C to 30°C. How much heat does the
rod lose?
3.
A 200 g hot water sample at 90°C is poured into 300 g
of cold water at 20°C. If the final temperature is 60°C,
how much heat was transferred by the hot water?

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