What is a Laboratory Thermometer? Video Lecture | Class 7 Oxford Science: Chapter Notes, Worksheets & Tests

hello friends this video on heat part 6
is brought to you by exam viacom no more
fear from exam so we learned about
clinical thermometer which is used only
to measure the temperature of human body
but do you think that we only need to
measure the temperature of human body
that is the only place where we need a
device to measure temperature not really
there are a lot of other things where we
also want to know the temperature for
example we want to know the temperature
of the environment during daytime
midnight we want to know the temperature
of boiling water we want to know the
temperature of a cup of coffee which is
quite on the temperature of ice cream so
how do we measure the temperature of all
these other objects now in clinical
thermometer we saw that the clinical
thermometer only has a specific range of
measurement it can only measure
temperature which falls below 35 degrees
I choose to 42 degrees anxious so now if
I try to use the same clinical
thermometer to measure the boiling point
of water
the thermometer would break because
boiling point of water is far more when
compared to the scale which is available
on the fidus clinical thermometer so
that is why came out the laboratory
thermometer which has a more broader
scale so here the temperature ranges
from minus 10 degree Celsius to 110
degree section so you see a huge range
of temperatures can be measured using
using this thermometer so it is used to
measure temperatures of a variety of
objects so now you might see that okay
then this can also measure the
temperature of human body because the
human body is temperature range also
falls within this this range so we will
see that limitations a little later that
how laboratory thermometer is different
from clinical thermometer and why it
cannot be used to measure human body
temperature so this thermometer can be
used to measure temperature of other
objects like maybe
temperature of water temperature of any
other liquid temperature of anything
actually you can measure using this
laboratory thermometer now how do we
read a laboratory thermometer now the
basic concept of reading any thermometer
remains the same you just need to find
out how much does one small line
represent in terms of degrees and that's
how you can just read the thermometer
but the way temperature is measured
using a laboratory thermometer is little
different from that we do with clinical
thermometer so let's see how laboratory
thermometer is different so here the
reading needs to be noted while the
thermometer bulb is in contact with the
object so one important difference
between laboratory and clinical
thermometer in terms of construction is
that the laboratory thermometer does not
have a king so in this case you do not
have a king therefore the mercury level
falls back immediately as soon as you
take the thermometer out of that object
so object and air force to the object
whose temperature we want to measure so
let us look at this picture which is
given on the screen let's say this
vessel contains water and let's say this
is and we want to measure the
temperature of this water so what do we
do we have put the thermometer here or
let's say here you have ice and we have
put the thermometer here so this is the
thermo meter now as long as the
thermometer remains inside the ice in
that case what happens the bulb of the
thermometer remains in contact with the
ice or here in this case the ice is
being melted to form the water here so
the bulb of the thermometer if it is in
contact with water it will be able to
measure the temperature of the water
because if the bulb is in contact with
water the water will heat up the bulb so
the mercury will expand the mercury
will rise and then we will really and we
will read the level till which the
market level has gone and that is the
reading of the thermometer but in this
case if you take like how in case of
human body we place the thermometer
under our tongue then we take it out and
then we read it why is that possible
because the mercury level does not fall
back but in this case if you try to do
the same thing like you first you insert
the thermometer inside water and then
you take it out as soon as you take it
out the mercury level will fall back so
you will not be able to read the
temperature so that is one very
important thing which you should
remember when you are using a laboratory
thermometer so whenever you use
laboratory thermometer you have to
insert the thermometer and then
immediately you have to read the
thermometer to get the accurate
temperature so this temperature must be
read by the thermometer is inside the
water or eyes or whichever objects
temperature you want to measure so that
is first thing that has to be remembered
secondly the thermometer has to be hold
upright this is also different from that
of clinical thermometer in case the
thermometer you just put it whether it
is little slant or it is a little side
means doesn't matter just that the bulk
should be under your town and the bulb
should be in contact with the surface of
your mount so that's the only criteria
but in this case you should not tilt the
thermometer because when you tilt the
thermometer again as you change the
position of the thermometer the kind of
heat that is being available to the bulb
also changes and therefore the
measurement of the thermometer also
changes so it is very important that in
piece of laboratory thermometer it is
old exactly upright so and that's why
you will see that in most of the
laboratories the thermometer is also
provided with the clamp stand as you can
see here you have a stand here so nobody
is going to disturb the orientation of
the thermometer just fix the thermometer
put it inside the solution or the object
whose temperature you want to see and
then immediately you put a note the
temperature so that's the best way to
use laboratory thermometer
now
two things are important in laboratory
thermometer
they are also how the volatility
thermometer is different from clinical
thermometer and this also tells you why
it cannot be used to measure human body
temperature because in human beings and
is it possible that you place the
thermometer under your thumb and
simultaneously you read the temperature
that is not possible right you have to
take the thermometer out and then read
the temperature now as soon as you do
that with the laboratory thermometer
your motherly level is going to fall
back so you are not going to get any
temperature so laboratory thermometer is
not going to work as a clinical
thermometer even though it has the
temperature range of human beings but it
cannot measure the temperature of human
body another important thing to be noted
is that the bulk should never touch the
surface of the container for example
this is the container here because if
the bulk touches the surface of the
container again the proper heating of
the world gets disturbed so we want the
bulk to be surrounded from all sides
with the substance whose temperature
needs to be measured for example here if
we are measuring temperature of water we
want to this bulk to be surrounded with
water from all sides so the bulk should
never touch the surface of the container
which is containing the liquid whose
temperature needs to be measured so now
let us look at some of the precautions
which have to be taken while we are
dealing with a laboratory thermometer so
first thing is again the same we have to
handle it with care to prevent breaking
because even inside the laboratory
thermometer there is mercury because
constructionwise
it is almost the same as a clinical
thermometer so it is heater is made up
of glass and inside the glass tube you
have mercury so it breaks then disposing
the mercury will become a tedious job
wash before and after use again it is
also a similar precaution which has to
be followed for all thermometers core
thermometer such that the world is
surrounded by the object on all sides
and this object reference to the
check whose temperature needs to be
measured so that is why if you want to
measure temperature of a cup of coffee
so insert the thermometer
such that the bulb is completely dipped
inside the coffee but at the same time
the bulb should not touch the surface of
the cup which contains the coffee do not
tilt the four thermometer while
measurement because when you place the
thermometer the reading also changes
because as you saw that here the mercury
level falls back very easily now the
same question why can't we use
laboratory thermometer to measure body
temperature now as I mentioned if you
just look at the scale of measurement
which is provided in both clinical and
laboratory thermometer so what do you
see in clinical thermometer we can
measure temperature any temperature
falling between 35 degree Celsius to 40
degree Celsius now if you look at a
laboratory thermometer you can measure
any temperatures between minus 10 degree
Celsius to 110 degree Celsius so
basically this temperature range also
falls within the laboratory thermometers
temperature range but the problem is
that with laboratory thermometer as soon
as you take it out from the substance
the mercury level immediately falls down
so when you put the thermometer inside
the amount of a patient as soon as you
will take it out of the mouth so the
mercury level is going to fall back so
you will not be able to read the
temperature so this is the reason why
the laboratory thermometer cannot be
used to measure body temperature thank
you please visit www.gfi.com/webmonitor
updates thank you once again