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Unit 13: Thermodynamics Page 13
scale was made more precise and Many of our measuring systems
today body temperature is usually started rather arbitrarily and then,
around 98.6°F. due to standardization over time,
became the systems we use today.
Later, (still 18th century) Mr.
Celsius came along and created his
What is Temperature
scale. He decided that he was
Measuring?
going to use water as his standard.
He chose the temperature that So that’s how temperature is
water freezes at as his 0° mark. He measured, but what is temperature
chose the temperature that water measuring? Temperature is
boils at as his 100° mark. From measuring thermal energy which is
there, he put in 100 evenly spaced how fast the molecules in
lines and a thermometer was born. something are vibrating and
moving.
Last but not least Mr. Kelvin came
along and wanted to create The higher the temperature
another scale. He said, I want my something has, the faster the
zero to be ZERO! So he chose molecules are moving. Water at
absolute zero to be the zero on his 34°F has molecules moving much
scale. more slowly than water at 150°F.
Temperature is really a molecular
Absolute zero is the theoretical
speedometer. This demonstration
temperature where molecules and
may make this clearer.
atoms stop moving. They do not
vibrate, jiggle or anything at
Sensing Temperature
absolute zero. In Celsius, absolute
zero is -273 ° C. In Fahrenheit, When something feels hot to you,
absolute zero is -459°F (or 0°R). It the molecules in that something
doesn’t get colder than that! are moving very fast. When
something feels cool to you, the
As you can see, creating the
molecules in that object aren’t
temperature scales was really
moving quite so fast.
rather arbitrary:
Believe it or not, your body
“I think 0° is when water freezes
perceives how fast molecules are
with salt.”
moving by how hot or cold
“I think it’s just when water
something feels. Your body has a
freezes.”
variety of antennae to detect
“Oh, yea, well I think it’s when
energy. Your eyes perceive certain
atoms stop!”
frequencies of electromagnetic
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