Textbook Exercises

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Q1. The normal temperature of a healthy human being is close to… (i) $98.6^\circ C$ (ii) $37.0^\circ C$ (iii) $32.0^\circ C$ (iv) $27.0^\circ C$

Answer: (ii) $37.0^\circ C$

Explanation: The normal human body temperature is approximately $37.0^\circ C$. Note that $98.6$ is correct only if the scale is Fahrenheit ($^\circ F$), but option (i) says $^\circ C$, which would be boiling hot!

Q2. $37^\circ C$ is the same temperature as… (i) $97.4^\circ F$ (ii) $97.6^\circ F$ (iii) $98.4^\circ F$ (iv) $98.6^\circ F$

Answer: (iv) $98.6^\circ F$

Explanation: This is the standard conversion for normal body temperature.

Q3. Fill in the blanks: (i) The hotness or coldness of a system is determined by its ________. (ii) The temperature of ice-cold water cannot be measured by a ________ thermometer. (iii) The unit of temperature is degree ________.

Answer: (i) Temperature (ii) Clinical (Because the range of a clinical thermometer is 35-42°C, and ice is 0°C). (iii) Celsius (or Fahrenheit)

Q4. The range of a laboratory thermometer is usually… (i) $10^\circ C$ to $100^\circ C$ (ii) $-10^\circ C$ to $110^\circ C$ (iii) $32^\circ C$ to $45^\circ C$ (iv) $35^\circ C$ to $42^\circ C$

Answer: (ii) $-10^\circ C$ to $110^\circ C$

Q5. Who do you think followed the correct way for measuring temperature? Refer to Figure 7.6 in textbook (Student 1: Tilted, Student 2: Not immersed properly, Student 3: Touching bottom, Student 4: Vertical and suspended).

Answer: (iv) Student 4

Explanation:

• Student 1 is holding it tilted.
• Student 2 is holding it too high (bulb barely touches water).
• Student 3 is touching the bottom of the container.
• Student 4 is holding it vertically, immersed in water, without touching the sides or bottom. This is the correct method.

Q6. Colour to show the red column on the drawings of thermometers as per the temperatures written below:

• $14^\circ C$
• $17^\circ C$
• $7.5^\circ C$

Q7. Observe the part of thermometer shown in Fig. 7.8 and answer: (Figure shows a scale with 10 divisions between 0 and 10, and 10 and 20. The liquid level is not explicitly defined in text but usually asks for least count or specific reading).

(i) What type of thermometer is it? It is likely a Laboratory Thermometer because the range shown includes 0 to 40°C with uniform divisions, typical for lab use.

(ii) What is the reading of the thermometer? Assumption based on typical textbook image: If the red line is at the 2nd small mark after 20, the reading is $22^\circ C$.

(iii) What is the smallest value that this thermometer can measure?

• Difference between big marks (0 to 10) = $10^\circ C$.
• Number of divisions = 10.
• Least Count = $10 / 10 = 1^\circ C$.

Q8. A laboratory thermometer is not used to measure our body temperature. Give a reason. Answer: A laboratory thermometer does not have a “kink” or constriction near the bulb. Therefore, the mercury/alcohol level falls immediately as soon as it is taken out of the mouth (or contact with the body), making it impossible to get an accurate reading of body temperature.

Q9. Vaishnavi’s Temperature Record (Table 7.4 Analysis)

(i) Highest recorded temperature? Answer: $40.0^\circ C$ (Recorded on Day One at 7 pm).

(ii) On which day and time? Answer: Day One at 7 pm.

(iii) When did temperature return to normal? Answer: Normal body temp is approx $37.0^\circ C$. Looking at the table, on Day Three at 4pm, the temperature was $37.0^\circ C$.

Q10. If you have to measure the temperature 22.5 °C, which thermometer will you use? (Fig 7.9 shows three thermometers with different least counts)

• (a) Divisions of 1 degree ($0, 1, 2...$)
• (b) Divisions of 0.5 degree ($0, 0.5, 1...$) - Implied by 2 divisions per degree
• (c) Divisions of 2 degrees ($0, 2, 4...$)

Answer: You should use thermometer (b).

Reason: To measure $22.5^\circ C$ accurately, the thermometer must have a least count of at least $0.5^\circ C$. A thermometer with 1-degree markings can only read 22 or 23 reliably.

Q11. The temperature shown by the thermometer in Fig. 7.10 is… (i) $28.0^\circ C$ (ii) $27.5^\circ C$ (iii) $26.5^\circ C$ (iv) $25.3^\circ C$

Answer: (iii) $26.5^\circ C$

Reason: (Based on visual interpretation of standard textbook diagrams). If the mark is halfway between 26 and 27, it is 26.5. If the divisions are 0.5 degrees, this reading is possible.

Q12. A laboratory thermometer has 50 divisions between 0°C and 100°C. What does each division measure? Answer:

• Temperature difference = $100 - 0 = 100^\circ C$.
• Total divisions = 50.
• Value of 1 division = $\frac{100}{50} = 2^\circ C$.

Q13. Draw scale between 10°C and 20°C with smallest division 0.5°C. (Self-Practice Drawing): You would draw the mark 10 and 20. Between them, you would place 19 small lines to create 20 gaps (since $10 / 0.5 = 20$ divisions).

Q14. Komal has a fever of 101 degrees. Is it Celsius or Fahrenheit? Answer: It is on the Fahrenheit scale ($^\circ F$).

Reason: $101^\circ C$ is above the boiling point of water. A human cannot survive at that temperature. In Fahrenheit, $101^\circ F$ indicates a moderate fever (normal is $98.6^\circ F$).