This document provides notes regarding topic 3 in IB physics regarding thermal physics. These notes were taken keeping the syllabus in mind and have aided me in getting a 6/7 in higher level IB physics
to explain what makes an object hot or cold .
what objects are made up of must be examined
the Greek thought experiment :
Take a gold piece and keep cutting it in half
Is it possible to keep cutting the gold piece in half forever ?
Conclusion Eventually the will be small it cannot be cut
gold piece so any
:
,
further
They called the smallest part of the matter atom
they believed each substance has its own atom (such as gold & air atom )
modern implications of atoms:
We assume . . .
atoms
perfectly are elastic spheres ( kinetic energy and momentum are conserved
during collisions ) .
element : matter made with a
single type of atom
compound matter : made with two or more types of atom joined together
unified mass unit : 112 of carbon -12 atom's mass G. 661×10-7
This for the smallest atom
mass is the mass :
hydrogen .
mole "
"
it means
you have 6.02×1023 things
:
This is avogadro 's constant (unit particles per mole).
:
molar mass :
the mass of one mole of atoms or molecules .
"
molar mass __
(mass of substance ) ( number of moles of a substance )
internal energy
internal energy the :
sum of kinetic and potential energy of molecules .
internal kinetic
energy
all substances are made up of molecules that are in constant motion meaning
they must have kinetic
energy "
the movement of particles happens in three
ways ( called the degrees of freedom
"
)
1. move in three dimensions ( random translation )
2. rotational
3. vibrating
, internal kinetic
energy
absolute temperature : a measure of average kinetic energy of the molecules of a
substance
average kinetic energy of molecules is
directly proportional to absolute temperature in
Kelvin
A
greater T means more movement of molecules and thus a
greater volume
Average kinetic energy is 0 at . . .
-
273° Celsius
0° Kelvin
TK =
To +273
internal potential energy
this potential energy is known as the intermolecular forces
the intermolecular forces (IMF) is electrical in nature
IMF in different states of matter :
1. solid :
substantial
2. liquid between :
solid & gas
3.
gas
:
negligible
In
chemistry terms . potential energy is chemical energy stored in the chemical bonds
thermometer
only measures the temperature of
mercury
thermometer will be in thermal contact causing a thermal interaction between the
two substances .
heat the thermal interaction between two
:
bodies in thermal contact
energy transferred from one
body to another as a result of a difference
in temperature ( also known as thermal energy ).
heat flows from hot to cold
thermal equilibrium : two bodies
having the same temperature causing heat to
stop flowing
thermal
In an isolated system ,
energy lost from a hot
body must be
in a
gained cold body .
heat transfer :
an increase or decrease in the internal energy
heat transfer
conduction heat transfer when bodies
:
are in contact with each other ( molecules collide)
convection heat transferred through fluids
:
c§Ñ warm
air
←caddis heater
hotter fluid occupies more volume and is less dense creating a
air rises
µg
• heats
sinks
buoyancy force acting on the hot air This causes the cold air to .
cold air 9
,
sink /fall
radiation does : not require media between two bodies (the only way heat can be transferred
through a vacuum .
dark colors emit /absorb radiation better
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