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PART 1
1.What is temperature?
Temperature is the degree or intensity of heat present in a substance orobject, especially as expressed according to a comparative scale and
shown by a thermometer or perceived by touch.
2. Identify Physical properties which vary with temperature and
which therefore maybe used as the basis for measurin temperature.
• !enth- as a substance is heated the length will increase for
example. a copper rod• "olume- as temperature is increased the volume increases for
example. gases, metals
• Resistance- as temperature increases particles in a solid move more
vigorously and restrict the flow of electrons.
• Pressure- as temperature increases pressure increases because there
is more collisions between the particles and container, increasing
the force within the same area.
#. $efine fi%ed points on the &elsius scale 'upper and lower fi%ed
points(
A fixed point is a melting or boiling point of a pure substance
therefore it will always have the same value on a scale foe example.
The upper and lower fixed point of the Celsius scale.
• The upper fixed point is the boiling point of pure water 1!!
degrees Celsius"
• The lower fixed point of water is the free#ing point of pure
water ! degrees Celsius"
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• $ixed points are used as reference points to determine
temperature of other substances
). *se of a thermometer to its desin
H ighlight design features which make a thermometer suitable
for its particular task:
• %ensitivity
&ange
'ortability
(urability
&esponse time
)ase of &eading
Draw and explain design of:
!aboratory Thermometer
%ensitivity- a laboratory thermometer is deined to be sensitive
to chanes in temperature by bein made of very thin lass
which reduces the time ta+en for heat to pass throuh the lass
&ange- it is made usin either mercury or alcohol'coloured(
because alcohol has a rane of ,11) to - derees &elsius and
mercury has a rane of ,#./ to #0.- derees &elsius
'ortability, small and compact therefore easy to move around.
(urability, made with lass which is firm and not damaed bythe heat.
&esponse Time, made with a thin central bore sometimes called
a thread because of its thinness therefore not a lot of the li3uid
needs to be heated to et a rise in temperature.
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)ase of &eading, this is ensured by usin mercury which is
briht silver or coloured alcohol
&linical Thermometer
%ensitivity, same as laboratory thermometer e%cept it has an
indentation in the bore to prevent mercury from oin bac+
into the bulb
&ange, 20 to )0 derees &elsius
'ortability, same as laboratory thermometer
(urability, same as laboratory thermometer &esponse time, same as laboratory thermometer
)ase of reading, same as laboratory thermometer
Thermocouple Thermometer
This is two different very thin conduction wires joined at the ends
to create two junctions, this instrument wor*s off the concept of
resistance or voltage change resulting in temperature change
%ensitivity, it can detect e%tremely small temperatures
&ange, it has an infinite ran because it is a comparison
and it can detect very hih temperatures of hundreds of
4elvin
'ortability, not very portable bul+y however it allows
remote temperature ta+in. (urability, very durable the wire is very stron 'metals(
and the meter isn5t in direct contact with whatever is bein
measured
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&esponse Time, very fast response time because the metals
are ood conductors of heat.
)ase of &eading, the meters are easy to read because it is
easy to read the analo and diital meters. 6owever it isdifficult to convert the voltae or resistance to temperature
PART 2
'1.1( Thermal energy is what we call energy that comes from heat.
+hen heat is given to a substance, its si#e usually increases. n other
words the substance expands on heating. Thermal e%pansion is thetendency of matter to change in volume in response to a change in
temperature, through heat transfer .
$or example, a cup of hot tea has thermal energy in the form of *inetic
energy from its particles. +hen you pour some mil* into your tea, some
of this energy is transferred to the particles in cold mil*. The cup of tea
is cooler because it lost thermal energy to the mil*.
+hen a substance is heated, its particles begin moving more and thus
usually maintain a greater average separation. aterials which contract
with increasing temperature are unusual this effect is limited in si#e, and
only occurs within limited temperature ranges. Thermal expansion can
be used in bimetallic strips in thermostats it can also be used in
loosening nuts and bolts. A thermometer wor*s by using the thermal
expansion of a li/uid to measure temperature. A hot-air balloon uses the
thermal expansion of air to generate lift. +hen a solid is heated, its
molecules gain *inetic energy and vibrate more vigorously. As the
vibration become larger, the molecules are pushed further apart and the
solid expands slightly in all directions.
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0n a hot day concrete runway
sections in airport expands and
this cause crac*ing. To solve this
problem we leave small gabs between sections.
0n a hot day concrete bridges
expand. To solve this problem,
we leave small gab at one end
and support the other end with
rollers.
Telephone wire contract on cold
days. To solve this problem, we
leave wires slac* so that they are
free to change length.
0n a hot day railway lines
expand. To solve this problem,
gaps are left between sections of
railway lines to avoid damage of
the rails as they expand in hotweather.
7ome applications that uses the e%pansion of li3uids
A physical chane is an e%ample of thermal e%pansion of a fluid.
The molecules move further apart when heated or closer when
cooled.
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1. Thermometers
. The valve shown below operates based on the expansion of the
oil. As the room warms of the oil in the valve expands and pushesthe piston down. This shuts off the flow of hot water. +hen the
temperature drops the valve opens again.
n physics, thermal conductivity often denoted k , λ, or κ " is the
property of a material to conduct heat. %ubstances that allow thermal
energy to move easily through them are called conductors. etals are
good conductors of thermal energy.In crystalline materials the phase and crystallite si8e are important.
In porous solids the thermal conductivity heavily relies on void
fraction pore si8e and the fluid contained in the pores.
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+ater is a poor conductor of heat. )ven though when you heat water in a
pan it gets hot /uic*ly....... it still is a poor conductor of heat, because the
force of attraction between the particles is not as strong as those in solids
and the particles move freely about the li/uid. 2ence, when heat is passed through the li/uid, it ta*es a longer time for the particles to
collide with one another and passing the heat energy to the other
particle.
PART )
79!I$7 !I:*I$7 A;$ <A7=7
There are three states of matter3
• %olids
• 4i/uids
• 5ases
7olids have particles that are held together firmly and uniformly and aretightly pac*ed. %olids are also incompressible and have high density.
This is due to strong intermolecular forces. %olids are non-fluid because
the molecules are in a rigid, closely bonded state. These molecules with
vibrate in place. %olids also have a definite shape and volume.
!i3uids have particles that are held together but less tightly, strongly
and uniformly than solids. n li/uids, the intermolecular forces are
strong enough to *eep the particles together, but not in fixed positions.6ecause of the loose bond, li/uid molecules are able to flow. 4i/uids
have a definite volume but not a definite shape. They ta*e the shapes of
their containers.
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<ases have particles that move freely. This is because the
intermolecular forces of gases are very wea*. 6ecause of this, gases are
the most fluid. 5ases have no definite shape or volume and therefore
will fill and ta*e the shape of its7 containers.
4inetic Particle Theory
This theory explains the properties of the different states of matter. The
particles in solids, li/uids and gases have different amounts of energy.
They are arranged and moved in different ways.
7olids,
1. 7olids have fi%ed shapes and are non,fluid> This is because the
particles cannot move from place to place.
. 7olids are incompressible> The particles are close together and have
no space to move into.
!i3uids,
1. !i3uids are fluid and ta+e the shape of their containers> The
particles can move around each other.
. !i3uids are incompressible> (espite fluidity, the particles are still
to close and have no space to move into.
<ases,
1. <ases are fluid and fill their containers> The particles can move
/uic*ly and in all directions.. They are compressible> The particles are far apart and have space
to move into.
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PART 0
').1( &onduction
n physics, thermal conductivity often denoted k , λ, or κ " is the
property of a material to conduct heat. %ubstances that allow thermal
energy to move easily through them are called conductors. etals are
good conductors of thermal energy.
In crystalline materials the phase and crystallite si8e are important.
In porous solids the thermal conductivity heavily relies on void
fraction pore si8e and the fluid contained in the pores.
+ater is a poor conductor of heat. )ven though when you heat water in a
pan it gets hot /uic*ly....... it still is a poor conductor of heat, because the
force of attraction between the particles is not as strong as those in solids
and the particles move freely about the li/uid. 2ence, when heat is
passed through the li/uid, it ta*es a longer time for the particles tocollide with one another and passing the heat energy to the other
particle.
').2( &onvection
Convection is the transfer of thermal energy from one place to another
by the movement of fluids e.g. air or water".
!and and 7ea ree8e>
(uring the day, the sun heats up both the ocean surface and the land.
2owever, water heats up much more slowly than land and so the air
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above the land will be warmer compared to the air over the ocean. The
warm air over the land will rise throughout the day, causing low pressure
at the surface. 0ver the water, high surface pressure will form because of
the colder air. To compensate, the air will sin* over the ocean. The windwill blow from the higher pressure over the water to lower pressure over
the land causing the sea bree#e.
At night, the roles reverse. The air over the ocean is now warmer than
the air over the land. The land loses heat /uic*ly after the sun goes down
and the air above it cools too. The ocean, however, is able to hold onto
this heat after the sun sets. This causes the low surface pressure to shift
to over the ocean during the night and the high surface pressure to moveover the land. This causes a small temperature gradient between the
ocean surface and the nearby land at night and the wind will blow from
the land to the ocean creating the land bree#e.
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Radiation
').)( (escribe experiments to investigate the factors on which
absorption and emission of radiation depend
Texture of surface rough, smooth" -
8ature of surface shiny, dull" - 0btain a hot piece of metal with two
different surfaces. 0ne shiny, one dull. 'lace a thermometer at each end
at e/ual distances from both surfaces. easure the temperature at each
end.
&esult3 the end with the dull surface has a higher temperature.
Conclusion3 the dull surface emits radiation at a faster rate heat leavesthe metal more /uic*ly through the dull surface.
Colour of %urface blac*, white" - 0btain two drin*ing glasses and place
a piece of white paper around one and a piece of blac* paper around the
other. 2alf fill each glasses with tap water of the same temperature.
'lace each glass beside each glass under the hot sun and leave them for
exactly two hours. t is recommended to do this at noon when the sun is
high and hot. After two hours, place a thermometer in each glass and
measure the temperature of the water.
&esult3 The glass covered in white has a lower temperature than the one
covered in blac*.
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Conclusion3 The white paper reflects the light and hence the lower
temperature of water. The dar* paper absorbs the light and traps it and
hence the higher temperature. (ar* colours are good conductors of heat
and will /uic*ly transfer the heat to the water.
Area of %urface - 0btain two table mats. 0ne should be a few
centimetres thic*er than the other. 'lace identical bowls of hot water on
each mat. easure the temperature of the water at intervals in order to
identify which bowl is losing water faster.
&esult3 The bowl with on the thinner mat loses heat faster because the
matter has a smaller surface area.
Conclusion3 2eat flow through the thic*er mat is slower because the
surface area is larger due to increased thic*ness.
').( &elate the principals of thermal energy transfer conduction,
convection, radiation" to the design of device.
The green house effect facilitates the growth of plants that need a warm
environment. This is especially the case in cold countries. &adiation
from the sun passes easily through the glass panels of a green house and
is absorbed by the plants and the soil inside. The plants also radiate
energy. This radiation is reflected by the glass panels and traps the
energy inside since it cannot pass through the glass roof. Thus the
temperature inside the green house increases until it reaches a thermal
e/uilibrium suitable for plant growth.