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Matter under the Microscope
Molecules in Motion
Pressure is the force acting per unit area (p = F
A ) . A particular force will have a different

effect on an object depending upon how large an area it acts on. The standard unit is
Pascal's. In a fluid, force…

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The equation for kinetic theory shows that there are three ways in which the pressure inside
a container can be increased:

1. More Molecules
- Putting more molecules inside the container with the volume staying
constant will increase the pressure, as pN
2. Decrease Volume
- Decreasing the volume will…

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o k = Boltzmann Constant = 1.38×10-23JK -1

From the ideal gas equation, there are three constants that can be changed. Assuming that
no molecules are added or taken away, the following relationship can be used.
p1V 1 p2V 2
T1 = T2

Temperature and Internal Energy:
The kinetic theory…

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Absolute zero is 0K, or -273.15 C. When working with the ideal gas equation and related
equations, temperatures must be given in Kelvin, so 273 must be added to any quoted
Celsius temperature.
Heat Engine and Cycles
First Law of Thermodynamics:
Different changes in a gas are defined by controlling…

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If the volume of a gas remains constant, we can say that there has been no work involved,
so W = 0 . This occurs in two instances:

U = Q
o Increase in internal energy as heat is supplied to the system
- U =- Q
o Decrease in…

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The Carnot cycle, as illustrated above, is composed of two isothermal paths and two
adiabatic paths. If thought of as a gas trapped in a cylinder by a piston, the piston will move
back and forth as the gas goes around the cycle.

It operates between a hot reservoir at…

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It can be shown that for an ideal gas undergoing a Carnot cycle, the thermal efficiency is
given by:
= TH

T H = Temperature of the hot reservoir
T C = Temperature of the cold reservoir

Internal Combustion Engine:
When a small quantity of high energy…

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(unlike the Carnot cycle) that is not continuous unless there is an input of energy (fuel).

During the cycle, work is done on the gas during the adiabatic compression and work is done
by the gas during the adiabatic expansion, meaning the area enclosed by the curve is the net…

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= Change in Temperature (K)

A material with a high specific capacity will require a lot of energy to raise its temperature. It
will also tend to retain the energy for a longer time

The main drawback for internal combustion engines is that they are extremely inefficient.
They typically convert…

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The second law of thermodynamics can be stated as "the entropy of a system can never
decrease, the best it can do is stay the same but almost always increase". Entropy (S) is a
measure of the disorder of a system, or the number of ways in which a certain…


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