3.4 – Thermal physics language
Allow about 10 mins
At the start of this topic, we encouraged teachers to use the word ‘heat’ only as a verb. “I am heating up the milk” or “it was heated over the Bunsen burner”. This is designed to reduce confusion between energy stored thermally and a temperature.
Temperature can be measured in a lot of different ways
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Fahrenheit / |
Celsius / |
Kelvin / |
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For a light-hearted take on why most people don’t use Fahrenheit anymore, listen here: |
Use degree Celsius when talking about a temperature. “I wish I’d worn my vest top… it was 33 degrees Celsius out there.” Use Celsius degrees when talking about a temperature change. “The tea was horrible; it had cooled by 33 Celsius degrees.” You write both as . A temperature of 24 centigrade means the same as 24 degree Celsius, but is not really used much anymore. |
This is measured on an absolute scale – that is is absolute zero; you cannot get any colder. To convert a temperature from degrees Celsius to kelvin add 273.15. A temperature difference of one kelvin ( is the same as a temperature difference of one Celsius degree (). |
As we discussed in 1.5 – Stores and pathways language, there is a lot of subtlety and nuance around our use of language and how our choice over words and key terminology can improve our teaching. Whilst this is useful reading early on in your teaching of thermal physics, it is also a section you may want to revisit once you have taught it once or twice.
The following is some guidance from the Institute of Physics about the language of thermal stores of energy, and some of the reasons why being careful with the language can help avoid student misconceptions.
Thermal transfers
For energy stored by a hot body (or at a change of phase)
Use the phrases:
“Energy stored thermally”,
“energy in a thermal store”.
Always avoid:
the word “heat” for the quantity that is stored.
For energy transfers due to a temperature difference:
Use phrases like:
“energy transferred by heating”,
“energy transferred due to a temperature difference”.
Avoid phrases like:
“heat transfer”,
“heat flow”,
“heat absorbed”.
To describe a rise in temperature:
Use phrases like:
“the temperature rose”,
“the kettle raised the water’s temperatures”.
Avoid phrases like:
“the tea heated up”,
“the kettle heated the water”.
Furthermore, use “temperature” in a way that helps to distinguish between raising the temperature and transferring energy by heating. This distinction is important because they are different effects (one is a phenomenon and one is a process). But, more importantly, they can occur independently. It is possible to:
- transfer energy by heating without raising the temperature (at a phase change)
- raise the temperature without transferring energy by heating; by transferring energy by working.
Transfer
This word has been used for some time in energy discussions. It is best to reserve it for energy being stored in one physical location (or system) and then in another.
Use phrases like:
“energy transferred from the hot water to the room”,
“energy transferred to the surroundings”.
Avoid phrases like:
“energy transferred from chemical energy to thermal energy”,
“energy transferred from a gravitational store to a kinetic store”.
3.3 – Conceptual heating/cooling