Temperature and its Measurement — Read Temperature Scales (2 of 3) · Learner pages

Lesson 1 · Find an instrument’s range

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

Name or initials: ____________   Date: ____________

An instrument’s range runs from its lowest stated measurement value to its highest. Read the actual endpoints and the unit. Range is different from the value of one small scale interval.

1. Read both endpoints. The illustrated model scale runs from −10 °C to 50 °C. Both labels are needed to report its range. Do not report only the largest label or assume the first mark is zero.
2. Interpret negative values. Values to the left of 0 °C on this horizontal model are below zero on the Celsius scale. For example, −5 °C is below 0 °C and above −10 °C. A negative Celsius value does not mean negative matter or no temperature.
3. Check a proposed reading. 8 °C lies between −10 °C and 50 °C, so it lies inside the stated range. 70 °C is greater than the upper limit and is outside. Being in range does not by itself prove that a device is suitable for a particular material or method.
4. Separate range from detail. Two instruments can have the same endpoints but different small divisions. The range tells where they can measure; the divisions tell what labelled detail the scale supports. Check both before selecting a device.

Worked example: A supplied device card gives −5 °C to 45 °C. A proposed 12 °C measurement is within the range, while −8 °C and 60 °C are outside. The lower limit matters just as much as the upper limit.

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

   1. −10 °C to 50 °C · 2. Only 50 °C · 3. 0 °C to 50 °C

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

   1. −20 °C · 2. 70 °C · 3. 8 °C

3. What does −5 °C mean?

   1. Five kilograms of coldness · 2. Five degrees below 0 °C on the Celsius scale · 3. No temperature exists

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

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

Lesson 2 · Work out the value of one interval

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

Name or initials: ____________   Date: ____________

To find a scale interval, subtract two labelled values and divide by the number of equal intervals between them. Count spaces, not the number of boundary marks.

1. Choose two clear labels. The model shows 20 °C and 30 °C. Their difference is 10 °C. Use the same unit for both and check that the intervening intervals are equal.
2. Count the spaces. There are five equal intervals between those endpoints. Six boundary marks create five spaces, so counting marks instead of spaces gives the wrong divisor.
3. Calculate one interval. Divide the 10 °C difference by five: each interval represents 2 °C. Moving one interval upward changes the reading by 2 °C, not 1 °C.
4. Use detail carefully. A scale with smaller divisions lets us record finer steps. This is resolution, not a guarantee of accuracy. An instrument can display fine steps and still be used incorrectly or need checking.

Worked example: An original scale has eight equal intervals between 10 °C and 14 °C. The difference is 4 °C, so one interval is 4 ÷ 8 = 0.5 °C. There are nine boundary marks, but the divisor is eight intervals.

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

   1. 5 °C · 2. 10 °C · 3. 2 °C

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

   1. Seven · 2. Five · 3. Six

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

   1. 0.5 °C · 2. 2 °C · 3. 8 °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.

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

Lesson 3 · Read a marked temperature scale

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

Name or initials: ____________   Date: ____________

After finding the interval value, locate the top of the liquid column. Start from a nearby label and count the steps to that level. Our horizontal strip is an enlarged scale model, not a complete thermometer.

1. Choose a starting label. The red column on the enlarged model ends between 20 °C and 25 °C. Begin at 20 °C. Check that each small interval is 0.5 °C before counting.
2. Count to the column top. There are nine half-degree intervals from 20 °C to the top marker. Count the spaces, including the last one that ends at the marker.
3. Combine base and steps. Nine intervals contribute 9 × 0.5 °C = 4.5 °C. Add the base: 20 + 4.5 = 24.5 °C. A reading near 25 °C is a sensible check.
4. Report only supported detail. For this task, report 24.5 °C. Do not invent digits such as 24.537 °C from a drawing with half-degree marks. If a real reading falls between marks, follow the stated estimation method and record uncertainty rather than pretending it is exact.

Worked example: A supplied scale has 1 °C intervals. The column ends three intervals above its 12 °C label. Its reading is 12 + 3 × 1 = 15 °C, not 3 °C. The base label remains part of the result.

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

   1. 29 °C · 2. 24.5 °C · 3. 4.5 °C

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

   1. 15 °C · 2. 3 °C · 3. 36 °C

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

   1. 24.537 °C with no uncertainty · 2. Exactly 24.500000 °C · 3. 24.5 °C

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.

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

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?

   Yes; endpoints determine every small mark / Yes; all thermometers use 1 °C divisions / No; their divisions can differ

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

   The upper limit automatically becomes 0 °C / It ignores the marked negative part of the scale / Nothing; all lower limits must be zero

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

   0.5 °C / 2 °C / 10 °C

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

   No; method and instrument performance still matter / Yes; extra digits guarantee correctness / Yes; incorrect positioning no longer matters

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

   Seven / Three and a half / Twenty-seven

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

   14 °C / 8 °C / 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 / Yes; every use is now suitable / Yes; no instructions are ever needed

2. Which gives both endpoints with unambiguous units?

   About sixty / A wide range / From −20 °C to 60 °C

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

   Four / Nine / Eight

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

   Always divide by ten instead / Use the number of spaces between the marks / Remove the temperature unit

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

   Stating that the reading lies between the two marks / Inventing many exact decimal digits / Naming the unit

6. Which sequence correctly reads a marked scale?

   Check the interval, choose a label, count steps and add / Ignore the labels and count all printed numbers / Always use the highest label