Temperature and its Measurement — Read Temperature Scales (2 of 3) · Answer guide

Lesson 1 · Find an instrument’s range

Read lower and upper limits and decide whether a required reading lies within them.

1. The model endpoints are −10 °C and 50 °C. Its range is…

   Answer: −10 °C to 50 °C. Both actual endpoints define the stated range.

2. Which value is inside the model range −10 °C to 50 °C?

   Answer: 8 °C. 8 lies between −10 and 50.

3. What does −5 °C mean?

   Answer: Five degrees below 0 °C on the Celsius scale. The minus sign places the value below zero Celsius.

Discuss: Create a range card with two endpoints and units. List two values inside and one outside, explaining each comparison.

Teaching note: Do not treat the largest number as the whole range. Do not confuse the total span with the value of one small interval. Open responses need discussion; they are not automatically marked.

Explain or demonstrate

For the stated range −5 °C to 45 °C, sort −8 °C, 12 °C, 44 °C and 60 °C into inside/outside. Explain one lower-limit and one upper-limit decision.

Evidence to include:

• All four values sorted
• Both limits used
• Range separated from smallest division

Review guide:

• 1 point: 12 and 44 inside
• 1 point: −8 and 60 outside
• 1 point: explanation uses the correct lower/upper comparison

Example response: 12 and 44 °C are inside. −8 °C is below −5 °C, and 60 °C is above 45 °C. The endpoints do not tell me the size of each small division.

Lesson 2 · Work out the value of one interval

Calculate a scale interval from two labels and a count of equal spaces.

1. The difference is 10 °C across five equal intervals. One interval is…

   Answer: 2 °C. 10 ÷ 5 = 2 °C per interval.

2. Six equally spaced boundary marks create how many intervals?

   Answer: Five. Each adjacent pair creates one space, so there is one fewer interval than marks.

3. There are eight intervals from 10 °C to 14 °C. Each interval represents…

   Answer: 0.5 °C. The difference is 4 °C; 4 ÷ 8 = 0.5 °C.

Discuss: Draw a scale from 10 °C to 14 °C with 0.5 °C intervals. Count the eight spaces and nine boundary marks, then explain why both counts are useful.

Teaching note: Every small mark does not automatically mean 1 °C. More marks or decimal digits do not automatically make a measurement accurate. Open responses need discussion; they are not automatically marked.

Explain or demonstrate

Draw and label a 10–14 °C scale with 0.5 °C intervals. State its interval count and boundary-mark count.

Evidence to include:

• Endpoints correctly labelled
• Equal steps correctly placed
• Intervals distinguished from boundary marks

Review guide:

• 1 point: eight equal intervals
• 1 point: nine boundary marks
• 1 point: 0.5 °C per interval explained

Example response: The 4 °C span has eight half-degree spaces and nine boundary marks. Labels from 10 to 14 increase by 0.5 °C each time.

Lesson 3 · Read a marked temperature scale

Read an original enlarged scale by combining a labelled starting point and counted intervals.

1. The model is nine 0.5 °C steps above 20 °C. What is its reading?

   Answer: 24.5 °C. 20 + 9 × 0.5 = 24.5 °C.

2. A column is three 1 °C intervals above 12 °C. Its reading is…

   Answer: 15 °C. 12 + 3 = 15 °C.

3. Which report is supported by the half-degree model reading?

   Answer: 24.5 °C. The drawing supports its marked half-degree value, not invented extra digits.

Discuss: Draw a 10–15 °C scale with 0.5 °C intervals and mark a reading of 13.5 °C. Explain the number of intervals above 10 °C.

Teaching note: Do not count from zero unless zero is the starting label. Do not report only the temperature increase from the chosen label as the whole reading. Open responses need discussion; they are not automatically marked.

Explain or demonstrate

Show 13.5 °C on an original 10–15 °C scale with 0.5 °C intervals and justify the position.

Evidence to include:

• Ten half-degree intervals across the full span
• Marker seven intervals above 10
• Number and unit stated

Review guide:

• 1 point: equally spaced correct scale
• 1 point: correct top marker
• 1 point: 10 + 7 × 0.5 = 13.5 °C

Example response: The full 5 °C span contains ten half-degree intervals. I mark the column seven intervals above 10 °C: 10 + 3.5 = 13.5 °C.

Final check · Set 1

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

1. Two instruments have the same endpoints. Must they have the same smallest division?

   No; their divisions can differ. Range and scale detail are separate features.

2. A scale begins at −10 °C. What is wrong with calling its lower limit 0 °C?

   It ignores the marked negative part of the scale. The actual lowest marked value is −10, not zero.

3. A 0 °C to 20 °C section has ten equal intervals. Each is…

   2 °C. 20 ÷ 10 = 2 °C.

4. Does a smaller displayed step automatically prove greater accuracy?

   No; method and instrument performance still matter. Resolution concerns detail; accuracy concerns closeness to the value being measured.

5. How many 0.5 °C intervals above 10 °C reach 13.5 °C?

   Seven. 13.5 − 10 = 3.5 °C; 3.5 ÷ 0.5 = 7 intervals.

6. A scale uses 2 °C intervals. The column is four intervals above 10 °C. Read it.

   18 °C. 10 + 4 × 2 = 18 °C.

Final check · Set 2

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

1. A required value fits a thermometer’s range. Is that enough to establish suitability?

   No; intended use and method must also be checked. Range is necessary but not the only suitability condition.

2. Which gives both endpoints with unambiguous units?

   From −20 °C to 60 °C. Both endpoint values and the temperature scale are stated.

3. For equal 0.5 °C intervals between 10 °C and 14 °C, how many spaces are needed?

   Eight. The difference is 4 °C; 4 ÷ 0.5 = 8 intervals.

4. A learner divides by the count of all endpoint marks. What should be corrected?

   Use the number of spaces between the marks. The temperature difference is spread over intervals, not the count of their boundaries.

5. The top lies between scale marks and no estimation rule is supplied. What should a learner avoid?

   Inventing many exact decimal digits. Extra unsupported precision misrepresents what the instrument shows.

6. Which sequence correctly reads a marked scale?

   Check the interval, choose a label, count steps and add. The reading needs both the base value and the interval contribution.