Temperature and its Measurement — Measure and Compare Data (3 of 3) · Answer guide

Lesson 1 · Plan a correct water measurement

Explain the placement and reading steps for a suitable laboratory thermometer in water.

1. For the illustrated liquid-in-glass water measurement, the bulb should be…

   Answer: Immersed and clear of the container’s sides and bottom. The bulb should measure the water without container contact.

2. Where should the eye be when reading the illustrated column?

   Answer: Level with the top of the liquid column. Eye-level viewing reduces errors from viewing angle.

3. Why read this laboratory thermometer while it remains immersed?

   Answer: Its reading can change when moved into different surroundings. The liquid column responds to its current surroundings.

Discuss: Annotate the supplied diagram with upright placement, submerged bulb, clearance from the container and eye-level reading. Explain one effect of removing the instrument before reading.

Teaching note: The water surface and the thermometer’s column top are different features. Align the eye with the column top to read this instrument; do not remove it first and assume its reading will remain fixed. Open responses need discussion; they are not automatically marked.

Explain or demonstrate

Annotate the supplied model with four correct placement or reading features. Explain why a reading taken after removal can differ.

Evidence to include:

• Upright placement
• Bulb immersed without side or bottom contact
• Eye at column top and reading taken while immersed

Review guide:

• 1 point: placement and immersion correct
• 1 point: eye-level and in-water reading
• 1 point: removal changes surroundings and can change the reading

Example response: The instrument is upright; the bulb is below the water surface and clear of the beaker. The eye is level with the column top and the reading is taken while immersed. After removal the bulb exchanges energy with different surroundings, so the reading can change.

Lesson 2 · Investigate different readings

Compare recorded temperatures and explain what agreement and disagreement can establish.

1. What is the spread of 28.0 °C, 28.5 °C and 28.0 °C?

   Answer: 0.5 °C. Spread is maximum minus minimum: 28.5 − 28.0 = 0.5 °C.

2. Two readings agree and one differs. What is the most careful response?

   Answer: Keep all records and investigate conditions and method. The pattern alone does not identify its cause.

3. Which could affect a scale reading?

   Answer: Viewing from above instead of eye level. Viewing angle can change where the column appears relative to the marks.

Discuss: For 21.0 °C, 21.5 °C and 21.0 °C readings of an intended stable sample, calculate the spread, name two possible causes and propose one fair repeat check. Keep the original data.

Teaching note: Agreement is not proof of accuracy, and a different result does not by itself prove carelessness. A thermometer need not rise continuously whenever energy is being supplied during a change of state. Open responses need discussion; they are not automatically marked.

Explain or demonstrate

For supplied readings 21.0, 21.5 and 21.0 °C, state the spread, two plausible explanations and one repeat check. Explain why agreement would not prove accuracy.

Evidence to include:

• Spread calculated
• Possible causes treated as hypotheses
• Repeat method controlled

Review guide:

• 1 point: 0.5 °C spread
• 1 point: two plausible method or condition factors
• 1 point: controlled repeat and distinction between consistency and accuracy

Example response: The spread is 0.5 °C. Different eye positions or a changing sample could contribute. I would repeat at the same position after checking stability and reading the same scale at eye level. Repeated agreement would show consistency, but a shared instrument error could remain.

Lesson 3 · Interpret daily air-temperature data

Read maximum and minimum temperatures, calculate daily differences and limit conclusions to the data.

1. For D3, maximum 31 °C and minimum 19 °C give a daily range of…

   Answer: 12 °C. 31 − 19 = 12 °C.

2. In the supplied data, which day has the highest maximum: D1 30, D2 32, D3 31, D4 29, D5 33 °C?

   Answer: D5. 33 °C on D5 is the largest maximum.

3. Which pair should be used for one daily range?

   Answer: The maximum and minimum for the same day and place. The range describes variation within the stated day at the place.

Discuss: Create a table from the five invented days with maximum, minimum and calculated range. Write two supported comparisons and one forecast claim that the data cannot justify. A later real-weather project can extend to ten attributed successive days.

Teaching note: A day’s maximum minus another day’s minimum is not that day’s range. A single room reading is not automatically the daily outdoor maximum or minimum. Open responses need discussion; they are not automatically marked.

Explain or demonstrate

Using maxima [30,32,31,29,33] °C and minima [20,21,19,18,22] °C for D1–D5, tabulate all five daily ranges and make two supported comparisons. Label the data as invented.

Evidence to include:

• Correct pairs used
• Five ranges calculated
• Comparisons limited to the supplied days

Review guide:

• 1 point: ranges 10,11,12,11,11 °C
• 1 point: D5 highest maximum and D3 widest daily range
• 1 point: invented-data label and no certain forecast

Example response: The invented daily ranges are 10, 11, 12, 11 and 11 °C. D5 has the highest maximum; D3 has the widest daily range. These observations do not establish next week’s weather.

Final check · Set 1

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

1. Why avoid holding a thermometer by its bulb?

   The hand can affect the sensitive part’s temperature. Hand contact can affect the measurement conditions.

2. A reading is changing because the sample itself is cooling. What should the record include?

   The measurement time and changing conditions. Time helps explain differences in readings of a changing sample.

3. Which plan best investigates a disputed reading?

   Repeat with the same stable sample and check placement, eye level and scale. A controlled repeat can test method-related explanations.

4. A supplied melting ice-water record stays constant under steady conditions. What can be concluded?

   A plateau can occur during melting; the record alone does not prove the instrument is stuck. Temperature can remain approximately constant during a change of state under suitable conditions.

5. D2 has 32/21 °C and D3 has 31/19 °C. Which has a wider daily range?

   D3, because 12 °C is greater than 11 °C. D2: 32 − 21 = 11; D3: 31 − 19 = 12.

6. What should a real weather table include besides temperature values?

   Dates, place, units and source. Context and source make records interpretable and checkable.

Final check · Set 2

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

1. Which position matches the supplied model?

   Upright with the bulb submerged and not touching the beaker. The correct placement keeps the sensitive bulb in the intended liquid.

2. An actual probe’s instructions require a different immersion depth. Which should be followed?

   The actual instrument’s instructions and approved setup. This diagram illustrates one instrument type, not every probe design.

3. A scale marked every 1 °C is reported as exactly 28.037 °C with no estimation method. What needs checking?

   Whether those extra digits are supported. Precision should match what the instrument and method can establish.

4. Readings of cooling water are taken at different times. What is a plausible reason for a difference?

   The sample temperature may have changed with time. Timing matters for a sample whose conditions are changing.

5. Can these five invented days prove that next week must be hotter?

   No; they do not establish a certain forecast. A short teaching dataset is not sufficient for such a forecast.

6. For D5, 33 °C maximum and 22 °C minimum give…

   An 11 °C daily range. 33 − 22 = 11 °C.