hey guys it's Kaeleigh in this lesson we're going to learn about thermometers
and how to read them thermometers are a tool that measure temperature have you
ever seen the weather report come on TV it will often look similar to this
and the weather man or woman will tell us the temperature prediction for the
next few days these numbers down here represent the temperature but what is
temperature temperature is a measure of how much heat or energy something has
there are a lot of tools that help us measure temperature but a simple way is
by using our senses now let's imagine you have a mug of cold milk and a mug of
hot tea if you wrap your hands around the mug of cold milk your hand will feel
cool and if you wrap your hand around the mug of hot tea your hand will feel
warm things that are cool to the touch have a lower temperature or less energy
and things that are warm to the touch have a higher temperature and more
energy now if we want a more precise measurement of temperature we can use a
thermometer thermometers are usually made of glass and have a hollow tube at
the bottom of the tube there is a bulb the bulb holds liquid normally and
alcohol there are numbers they go up the side of the thermometer normally there's
a symbol at the top that tells you what units of temperature you are measuring
these units are normally ac for Celsius or an F for Fahrenheit in the United
States we use Fahrenheit to describe temperatures but most other countries
use Celsius these are also thermometers thermometers that look like this often
give the temperature of engines or machinery and
type might be the most familiar to you this thermometer is used to take the
temperature of the human body you may have used one of these when you were
sick to see if you had a fever when there is an increase in heat the liquid
that is in the bulb will expand and push up the tube
so as the temperature goes up and gets hotter the liquid goes up in the
thermometer when there is a decrease in heat the liquid that is in the bulb will
contract and slide down the tube as the temperature goes down and gets colder
the liquid goes down in the thermometer now let's practice reading some
thermometers here we see the red line has moved up the tube we find the top of
the liquid and we see what number it is at on the scale this one is right at 80
and if we look at the top we see what units we're in and in this F so
Fahrenheit we can write the temperature as 80 with a degree symbol and then a
capital F for Fahrenheit here we see the red liquid has moved down in the tube we
find the top of the liquid and we see what number it is at on the side this
one is right at 30 I'm gonna look at the top to see what units were in and it's C
so Celsius so you can write the temperature as 30 with a degree symbol
and then a capital C for Celsius now let's compare these two thermometers
what temperature does the blue one read we can find the top of the liquid and it
reads 70 degrees and Celsius now the red one we find the top of the liquid and it
is 90 degrees and Celsius so which thermometer is reading a hotter
temperature yeah the red one the liquid has raised up higher so the scale gives
us a larger number now these thermometers don't have numbers
but they're all in Fahrenheit just by looking at the heights of the liquid
which thermometer is measuring the hottest temperature yeah this one we
know because the liquid has gone all the way up to the top and is higher than the
other thermometers now which thermometer is measuring the coldest temperature
right it's this one here and how do we know because the liquid is the lowest
and we know that as the liquid cools it slides back down the tube let's talk
about some common temperatures we feel in the real world the human body is on
average 98.6 degrees Fahrenheit which is the same as 36.6 degrees Celsius even
though these look like different temperatures on the thermometer they are
actually the same they're just being measured in different units a nice sunny
day could be about 70 degrees Fahrenheit but a super hot day where you definitely
want a pool to swim in could be about 90 degrees Fahrenheit and a day when it is
snowing could be about 30 degrees Fahrenheit and when we bake cookies we
typically heat the oven to 350 degrees Fahrenheit that's really hot now you
know how to read a thermometer and why we use them remember to always check the
units at the top practice what you've learned by doing the online games and
quizzes have fun and remember to always be clever