Chapter 4 Key Terms
Body Temperature – an important indicator of health. A normal human body temperature is 37
degrees Celsius.
Hypothermia – The condition where your body temperature drops a few degrees below 37 degrees
C. The heart slows down and organs do not function properly.
Room Temperature – The temperature at which most people are comfortable. Usually between 20
and 23 degrees C.
Bimetallic Strip – This strip is made from two different types of metals that expand by different
amounts when heated.
Calibrate – To accurately assign the numbers on a scale.
Celsius Scale – The most common scale for measuring temperature. On the Celsius scale, water
at sea level boils at 100 degrees C and freezes at 0 degrees C. Developed by Anders Celsius.
Fahrenheit Scale – The first widely used temperature scale. On the Fahrenheit scale water at sea
level boils at 212 degrees F and freezes at 32 degrees F. Body temperature is 98.6 F
- Coldest thing that could be generated in Fahrenheit’s time was a mixture of sale, water and ice
(assigned a value of 0 F).
Kelvin Scale – A scale used for measuring temperatures in scientific experiments. On the Kelvin
Scale, pure water freezes at 273 K and boils at 373 K. The coldest possible temperature (also
known as absolute zero) is 0 K (which is about -273.15 C). Developed by Lord Kelvin.
Thermocouple – Used to measure temperature Thermocouples are made of two different types of
metal wires that are connected at both ends. Temperature differences between the ends cause an
electric current to travel along the wires.
- Very simple and more durable than most other temp measuring devices
- Can be used to measure much higher temps than typical thermometers
Thermogram – image generated by a device that detects infrared radiation and converts it into colors
that represent temperature differences. Shows areas where heat is at its greatest and its lowest
- Red/Orange areas show where the heat is escaping
- Blue/Green areas show where heat is retained
- Can help to show where heat loss needs to be prevented
Thermometer – a device used to measure temperature.
Thermoscope – developed before thermometers. A thermoscope, developed by Galileo in 1596,
shows whether the air is hot or cold but does not measure temp (NOT called a thermometer) since
there is not numerical scale. Did NOT show how hot or cold the air was.
Common Temperatures to Remember:
Body Temperature: 37 C
Boiling Point of Water: 100 C
Room Temperature: 20 – 23 C
Freezing Point of Water: 0 C
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If body temperature is above 37 C it indicates you have an illness or infection
Above 40 C the heat can harm you, especially tissues in the brain
Too low of a temperature can cause damage as well (hypothermia – organs do not function
properly, heart slows down)
Example of animal that has body temperature to suit their needs:
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Arctic cod live in waters so cold that would freeze other fish.
They have a chemical that acts like antifreeze in their bodies that prevents their tissues from
freezing.
Animals that are affected by the temperature of their surroundings
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Cold Blooded animals have a body temperature that is affected by their surroundings
They cannot generate enough heat to keep their body temperatures constant
Lizards
Bimetallic Strip
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Thermostats that turn a furnace off and on have a device in them called a bimetallic strip
Made of two different metals that expand by different amounts when heated
When heated a bimetallic strip bends because one of the metals in the strip expands more
than the other.
The strip when heated bends away from the metal that expands the most
Liquid In-Glass Thermometer
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Cheap and accurate
Glass cylinder with a capillary hole in the cylinder and a bulb at one end filled with mercury or a
red coloured fluid. Has an engraved temp scale
Can measure temps from -200 C to 600 C
One of the earliest thermometers (used in Medicine, Industry, etc)
**** HOW IT WORKS***
When the thermometer touches something hot, the liquid inside the glass moves up the tube
(liquid gets bigger)
When it touches something cold, it moves down the tube (liquid gets smaller)
When the thermometer is just as hot or cold as the thing it is touching, it stops moving.
Digital Thermometers – its now common to measure temperature with electronics like digital
thermometers
Infrared Thermometers
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All objects give off infrared radiation (which is at different temperatures).
Your eyes cannot see it
Some film and electronic detectors, can sense different temps and can change infrared radiation
into different colours that can be seen as temp differences
Thermograms show areas where heat is at its greatest and its lowest
Red/Orange areas show where the heat is escaping
Blue/Green areas show where heat is retained
Can help to show where heat loss