Temperature and its Measurement — Evidence, Scales and Instruments (1 of 3) · Answer guide

Lesson 1 · Use measurement beyond touch

Explain why sensations alone cannot reliably compare temperatures.

1. Two hands feel the same water differently after different prior conditions. What does this show?

   Answer: Sensation alone can be unreliable for comparing temperature. Prior experience can affect a sensation of hot or cold.

2. Which instrument measures temperature?

   Answer: Thermometer. A thermometer measures temperature; the other tools measure length or volume.

3. Which is the most complete temperature record?

   Answer: Water A: 25 °C at 10 am. The record identifies the sample, value, unit and time.

Discuss: Write a claim-evidence explanation for the supplied scenario. Include one reason to use a thermometer and one piece of information missing from a bare reading of “25”.

Teaching note: Feeling warmer does not always establish a higher measured temperature. Temperature is also different from the total energy transferred as heat. Open responses need discussion; they are not automatically marked.

Explain or demonstrate

Explain the two-hand supplied scenario using observation, conclusion and a complete instrument record.

Evidence to include:

• Different sensations acknowledged
• Same sample distinguished from sensation
• Number and unit recorded

Review guide:

• 1 point: sensation can depend on prior conditions
• 1 point: no claim of two simultaneous temperatures for the same sample
• 1 point: complete record with °C

Example response: Both hands are placed in the same water but can report different feelings because they were in different conditions before. The supplied instrument result is water B, 25 °C. The two feelings do not replace that measurement.

Lesson 2 · Read temperature scales and symbols

Use Celsius, Fahrenheit and kelvin symbols correctly and perform a supplied Celsius-to-kelvin conversion.

1. Which is the SI unit of temperature?

   Answer: kelvin (K). Kelvin is the SI temperature unit.

2. Which symbol is written correctly?

   Answer: K. The symbol for kelvin is capital K with no degree sign.

3. Using K = °C + 273.15, what is 20 °C in kelvin?

   Answer: 293.15 K. Add 273.15 to 20 to obtain 293.15.

Discuss: Correct these records with units and explain your corrections: “298.15 °K” and “37 is cooler than 98.6” when the original values were 37 °C and 98.6 °F.

Teaching note: Do not compare 98.6 and 37 as bare numbers when one is Fahrenheit and the other Celsius. Do not put a degree sign before K. Open responses need discussion; they are not automatically marked.

Explain or demonstrate

Express 22 °C in kelvin using the supplied rule. Explain why the room did not heat up when you changed the numerical scale.

Evidence to include:

• 273.15 added correctly
• K written without a degree sign
• Same temperature explained

Review guide:

• 1 point: 295.15 K
• 1 point: correct symbol and spacing
• 1 point: conversion changes representation, not the room

Example response: 22 + 273.15 = 295.15, so the reading is 295.15 K. It represents the same temperature as 22 °C; only the scale used to write it changed.

Lesson 3 · Choose a suitable thermometer

Check an instrument’s intended purpose, range and instructions before interpreting a measurement.

1. What should be checked first when choosing a thermometer?

   Answer: Its intended purpose, range and instructions. These properties determine whether a device is suitable for the task.

2. Model A measures 35 °C to 42 °C. Can it measure an 18 °C sample within its stated range?

   Answer: No; 18 °C is below its lower limit. 18 is less than 35, so it lies outside the stated range.

3. Which course activity is appropriate?

   Answer: Read supplied digital thermometer data. Supplied data supports learning without inappropriate device use.

Discuss: Using two supplied device cards, match one classroom measurement to a suitable instrument and state two pieces of evidence for the choice. Do not measure another learner’s body temperature.

Teaching note: A thermometer that has a digital display is not automatically suitable for every temperature or every body site. More digits also do not prove better accuracy. Open responses need discussion; they are not automatically marked.

Explain or demonstrate

Model A is clinical, 35–42 °C. Model B is laboratory, −10–110 °C. For supplied 18 °C water, choose a candidate and explain why range alone is not the entire decision.

Evidence to include:

• Range comparison
• Intended purpose checked
• Actual instructions acknowledged

Review guide:

• 1 point: B is the candidate
• 1 point: 18 lies within B and outside A
• 1 point: safe method and actual device instructions still required

Example response: B is the candidate because it is for laboratory work and 18 °C lies within −10 to 110 °C. A starts at 35 °C. I would still need the real instrument instructions and teacher-approved setup.

Final check · Set 1

Try one set after the lessons. Use the other set after reviewing any errors.

1. Why not test an unknown hot object by touch?

   A suitable instrument and safe method avoid relying on a potentially harmful touch test. A safe measurement does not require directly touching an unknown extreme.

2. A report says only “the temperature is 25”. What essential information is missing?

   The unit or temperature scale. Without a scale, the value is incomplete.

3. Convert 0 °C to kelvin using the supplied rule.

   273.15 K. 0 + 273.15 = 273.15 K.

4. Which record correctly includes the temperature scale?

   18 °C. Degree Celsius is a temperature unit; “degrees” alone leaves the scale unclear.

5. Does a digital display prove a thermometer is suitable for every task?

   No; purpose, range and method still matter. Display style does not establish measurement limits or approved use.

6. How does an infrared design differ from a contact design in this lesson?

   It can measure without the same direct contact, following its own instructions. Different sensing designs require their prescribed procedures.

Final check · Set 2

Try one set after the lessons. Use the other set after reviewing any errors.

1. Which is a measurement rather than only a sensation?

   The display reads 24 °C. A numerical reading with its unit is a measurement.

2. A reliable comparison between two cups should include…

   Readings made with a suitable instrument using a consistent method. Consistent measurement is more interpretable than unrelated sensations or shapes.

3. A supplied value is 25 °C. Its equivalent on the kelvin scale is…

   298.15 K. 25 + 273.15 = 298.15.

4. What does the familiar 37 °C body-temperature reference mean in this lesson?

   An approximate reference for comparing scales, not a diagnosis or a fixed value for everyone. People and measurement conditions vary. This lesson does not diagnose health.

5. Model B is marked −10 °C to 110 °C for laboratory use. What can be concluded about 18 °C?

   It is inside the stated range; method and purpose still need checking. −10 ≤ 18 ≤ 110, but range is only one suitability criterion.

6. A real device has a different range from the diagram. Which information should be used?

   The real device’s verified label and instructions. An illustration is not a specification for every product.