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Three Scales Thermometer

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About This MicroSim

Students memorise the formula and still cannot say why 5 °C of warming is not 41 °F of warming. The formula hides the reason. A shared physical column does not.

All three scales run alongside one column here, aligned to the same physical temperature. Two dashed guides cross the whole thing at 0 °C = 32 °F = 273.15 K and at 100 °C = 212 °F = 373.15 K. Look at where each scale puts its own zero: Celsius and kelvin have the same size degree and different zeros, Fahrenheit has a different size degree and a different zero.

Everything is stored internally in kelvin and derived from there, so the three readouts cannot drift out of agreement with each other.

Value mode converts a temperature and shows the arithmetic one step at a time - the multiplication by 9/5 on its own line, then the addition of 32 on the next.

Difference mode adds a second marker and reports the gap between them in all three units. Both Fahrenheit numbers carried the same +32, so it cancelled, and the panel says so explicitly. This is the misconception that otherwise stays invisible until it turns up in a student's own data.

Ten named temperatures are one click away, from absolute zero to boiling. Try dragging below 0 K and the sim will stop you: there is no temperature below absolute zero, because atoms cannot move less than not at all.

How to Use

  • Drag the marker on the column, or type into any of the three boxes at the bottom. The other two follow.
  • Click a named temperature in the left list to jump there.
  • Press Switch to difference mode and drag both markers. Read the difference in all three units, then read why the Fahrenheit number is what it is.
  • Try to drag below absolute zero.

Iframe Embed Code

You can add this MicroSim to any web page by adding this to your HTML:

<iframe src="https://iowerx.github.io/pi-env-monitor/sims/three-scales-thermometer/main.html"
        height="610px"
        width="100%"
        scrolling="no"></iframe>

Lesson Plan

Grade Level

6-12

Duration

15-20 minutes

Bloom's Taxonomy Level

Apply (L3)

Prerequisites

  • Multiplying by a fraction
  • Adding and subtracting negative numbers

Activities

  1. Alignment (5 min): In value mode, find where 0 C sits and where 0 F sits. They are not the same height. Explain what that means about the two scales.
  2. Convert (6 min): Cover the panel. For 25 C, 100 F and 200 K, work out the other two units yourself, then check.
  3. The difference (8 min): Switch to difference mode. Put A at 20 C and B at 25 C. Predict the Fahrenheit difference before you look. Then explain, in one sentence, where the 32 went.

Assessment

  • Converts in both directions between all three scales.
  • Explains why kelvin and Celsius differences are numerically identical.
  • States that a temperature difference does not take the +32 offset.

References

  1. BIPM, The International System of Units (SI) - the definition of the kelvin.
  2. NIST: temperature and the kelvin - what the 2019 redefinition changed and what it did not.
  3. Wikipedia: Absolute zero
  4. Wikipedia: Fahrenheit - where the odd zero point came from.