Science Chapter 7: Temperature and its Measurement - Exercises

📘 Chapter 7: Temperature and its Measurement

📝 “Let us enhance our learning” (Exercises)

Question 1. The normal temperature of a healthy human being is close to—
(i) 98.6 °C (ii) 37.0 °C (iii) 32.0 °C (iv) 27.0 °C

  • Answer: (ii) 37.0 °C

Question 2. 37 °C is the same temperature as—
(i) 97.4 °F (ii) 97.6 °F (iii) 98.4 °F (iv) 98.6 °F

  • Answer: (iv) 98.6 °F

Question 3. Fill in the blanks:

  • (i) The hotness or coldness of a system is determined by its temperature.
  • (ii) The temperature of ice-cold water cannot be measured by a clinical thermometer.
  • (iii) The units of temperature are degree Celsius, degree Fahrenheit and kelvin.

Question 4. The range of a laboratory thermometer is usually—
(i) 10 °C to 100 °C (ii) -10 °C to 110 °C (iii) 32 °C to 45 °C (iv) 35 °C to 42 °C

  • Answer: (ii) -10 °C to 110 °C

Question 5. Four students used a laboratory thermometer to measure the temperature of water as shown in Fig. 7.6. Who do you think followed the correct way for measuring temperature?

  • Answer: (iii) Student 3
  • Reason: When measuring temperature with a laboratory thermometer, it should be held vertically (not tilted), and its bulb must be completely immersed in water without touching the bottom or sides of the beaker.

Question 6. Colour to show the red column on the drawings of thermometers (Fig. 7.7) as per the temperatures written below: (a) 14 °C (b) 17 °C (c) 7.5 °C

Drawing Guidance:

  • (a) 14 °C: Fill red color up to 4 small divisions above 10 °C.
  • (b) 17 °C: Fill red color up to 7 small divisions above 10 °C.
  • (c) 7.5 °C: Fill red color halfway between 7th and 8th division above 0 °C (or between 7 °C and 8 °C).

Question 7. Observe the part of thermometer shown in Fig. 7.8 and answer the following questions:

  • (i) What type of thermometer is it?
    Answer: It is a Laboratory thermometer.
  • (ii) What is the reading of the thermometer?
    Answer: The reading is 10 °C.
  • (iii) What is the smallest value that this thermometer can measure?
    Answer: The lowest temperature it can measure is -10 °C (and its least count/smallest division value is 1 °C).

Question 8. A laboratory thermometer is not used to measure our body temperature. Give a reason.

  • The liquid level in a laboratory thermometer begins to fall as soon as it is removed from the body/mouth, making it impossible to take an accurate reading.
  • Its temperature range (-10 °C to 110 °C) is too wide compared to the narrow range of human body temperature (35 °C to 42 °C).

Question 9. Vaishnavi has not gone to school as she is ill. Her mother has kept a record of her body temperature for three days as shown in Table 7.4. Answer the following questions:

  • (i) What was Vaishnavi's highest recorded temperature?
    Answer: 40.0 °C.
  • (ii) On which day and at what time was Vaishnavi's highest temperature recorded?
    Answer: Day 1 at 7:00 pm.
  • (iii) On which day did Vaishnavi's temperature return to normal?
    Answer: Day 3 (at 4:00 pm when it reached 37.0 °C).

Question 10. If you have to measure the temperature 22.5 °C, which of the following three thermometers will you use (Fig. 7.9)? Explain.

  • Answer: We will use the thermometer whose smallest division (least count) measures 0.5 °C.
  • Explanation: To measure a fractional temperature like 22.5 °C accurately, each small mark must represent 0.5 °C. A scale with 1 °C divisions cannot give a precise reading for 0.5 °C.

Question 11. The temperature shown by the thermometer in Fig. 7.10 is—
(i) 28.0 °C (ii) 27.5 °C (iii) 26.5 °C (iv) 25.3 °C

  • Answer: (iii) 26.5 °C

Question 12. A laboratory thermometer has 50 divisions between 0 °C and 100 °C. What does each division of this thermometer measure?

  • Calculation:
    Temperature range = 100 °C - 0 °C = 100 °C
    Value of 1 division = 100 °C / 50 = 2 °C
  • Answer: Each division measures 2 °C.

Question 13. Draw the scale of a thermometer in which the smallest division reads 0.5 °C. You may draw only the portion between 10 °C and 20 °C.

Drawing Instructions:

  • Draw two main long lines marked 10 °C and 20 °C.
  • Since the range is 20 - 10 = 10 °C, divide this space into 20 equal small divisions.
  • Every single small division will represent 0.5 °C (e.g., 10.5 °C, 11.0 °C, 11.5 °C, and so on up to 20.0 °C).

Question 14. Komal tells you that she has a fever of 101 degrees. Does she mean it on the Celsius scale or Fahrenheit scale?

  • Answer: She means it on the Fahrenheit scale (101 °F).
  • Explanation: Normal human body temperature is 37.0 °C (98.6 °F). Human body temperature never exceeds 42 °C. A temperature of 101 °C is higher than boiling water (100 °C), which is impossible for a living human being. Thus, fever in "101 degrees" is always expressed in Fahrenheit.

🔬 “Learning further” (Projects & Field Activities)

Measuring Body Temperature of Animals:

  • Veterinarians use specialized digital or rectum clinical thermometers to measure animal temperatures.
  • Average body temperatures: Dog/Cat: ~38.5 °C to 39.2 °C; Cow/Buffalo: ~38.5 °C; Horse: ~37.5 °C to 38.5 °C.

Hottest and Coldest Places in India:

  • Coldest Place: Dras / Kargil (Ladakh) – Winter temperatures drop down to -45 °C.
  • Hottest Place: Phalodi (Rajasthan) – Summer temperatures rise up to 51 °C.

Planets in Solar System (Distance vs Average Temperature):

Planet Order of Distance from Sun Average Temperature
Mercury 1st (0.39 au) 167 °C
Venus 2nd (0.72 au) 464 °C (Hottest planet due to thick atmosphere trapping heat)
Earth 3rd (1.00 au) 15 °C
Mars 4th (1.52 au) -65 °C
Jupiter 5th (5.20 au) -110 °C
Saturn 6th (9.58 au) -140 °C
Uranus 7th (19.2 au) -195 °C
Neptune 8th (30.1 au) -200 °C

Observation: Temperatures generally decrease with distance from the Sun, but Venus is hotter than Mercury because its thick carbon dioxide atmosphere traps heat through the greenhouse effect.

Anna Mani (1918–2001) – Weather Woman of India:

  • An Indian scientist who designed and built numerous weather measuring instruments, reducing India's reliance on imported devices and pioneering research in wind and solar energy.
💡 Teacher's Tip: Note down all these answers cleanly in your Science notebook. Handle thermometers with extreme care to prevent breakage and mercury spillage! 🌡️

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