Think and Answer
Q1. Can it always be correctly judged, that a person has fever, only by touching the person?
Answer:
No, it cannot always be correctly judged. Our sense of touch can be unreliable because our hands may be at different temperatures. For example, if a person's hand is cold, they may feel a normal forehead as warm, or if their hand is warm, they may not feel a slight fever. Always use a thermometer to accurately measure body temperature.
Check your progress
Q1. Do small children generally have slightly higher body temperatures as compared to adults?
Answer:
Yes, small children often have slightly higher body temperatures than adults. This is because their metabolism is faster and their bodies generate more heat. However, the normal temperature range for children is still around 36.5°C to 37.5°C, but they may be at the higher end of this range.
Q2. Do old people, even when healthy, generally have lower body temperatures than young adults?
Answer:
Yes, healthy elderly people often have slightly lower body temperatures than young adults. This is because as people age, their metabolism slows down, and their body's ability to regulate temperature changes. Their normal body temperature may be around 36.0°C to 36.5°C.
Q3. I have seen a friend of mine using a digital thermometer that reads temperature on a different scale. It shows the normal temperature of a healthy human body as 98.6 °F. What is the reason for this difference?
Answer:
The difference is because your friend's thermometer uses the Fahrenheit scale instead of the Celsius scale. The normal human body temperature is 37.0 °C, which is equivalent to 98.6 °F. Both scales measure the same temperature, just with different units. The Fahrenheit scale is commonly used in some countries like the United States.
Q4. Can a clinical thermometer be used for measuring the temperature of boiling water? Or for measuring the temperature of ice?
Answer:
No, a clinical thermometer cannot be used for measuring the temperature of boiling water or ice. Clinical thermometers have a limited range, typically from about 35°C to 42°C (or up to 43°C). Boiling water is around 100°C and ice is at 0°C, both far outside this range. Using a clinical thermometer for such extreme temperatures could damage it.
Q5. How can we measure temperatures beyond the range of a clinical thermometer?
Answer:
Temperatures beyond the range of a clinical thermometer can be measured using a laboratory thermometer. Laboratory thermometers have a wider range, typically from -10°C to 110°C, so they can measure the temperature of ice (0°C), boiling water (around 100°C), and many other substances.
Q6. Can we use a laboratory thermometer for measuring body temperature of a person?
Answer:
No, a laboratory thermometer should not be used for measuring body temperature. It is not designed for that purpose. The range of a laboratory thermometer is very wide (-10°C to 110°C), so it may not be accurate for the narrow range of human body temperature. Also, laboratory thermometers are fragile and may break if placed under the tongue or in the armpit. Clinical thermometers are specifically designed for safe and accurate body temperature measurement.
LET US ENHANCE OUR LEARNING
Q1.
- 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:
37.0°C
Q3.
- 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
Q4.
- 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 (iii) Celsius (also correct: degree Fahrenheit, with unit denoted °F; the commonly used answer expected here is Celsius, since clinical/lab thermometers in the chapter use the Celsius scale)
Q5.
- 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
Q6.
- Four students used a laboratory thermometer to measure the temperature of water as shown in Fig. 7.6 (Student 1, 2, 3, 4 shown holding the thermometer in different ways). Who do you think followed the correct way for measuring temperature? (i) Student 1 (ii) Student 2 (iii) Student 3 (iv) Student 4
Answer:
(iii) Student 3 — the student who holds the thermometer vertically with the bulb fully immersed in the water without touching the sides or bottom of the container, following the correct method described in the chapter (thermometer held vertically, bulb immersed, not tilted, not touching the container walls or base).
Q7.
- Question: Colour to show the red column on the drawings of thermometers (Fig. 7.7) as per the temperatures written below: 14°C, 17°C, 7.5°C.
Answer:
This is a drawing/colouring task. The red liquid column should be shaded from the bulb at the bottom up to the mark corresponding to each given temperature: up to the 14°C mark on the first thermometer, up to the 17°C mark on the second thermometer, and up to the halfway point between the 7°C and 8°C marks (i.e., the 7.5°C mark) on the third thermometer.
Q8. Observe the part of thermometer shown in Fig. 7.8 and answer the following questions: (i) What type of thermometer is it? (ii) What is the reading of the thermometer? (iii) What is the smallest value that this thermometer can measure?
Answer:
(i) It is a laboratory thermometer (shown as a horizontal glass tube with a Celsius scale, of the type used to measure temperatures like boiling water or ice, unlike a digital clinical thermometer). (ii) The reading of the thermometer, as shown by the red liquid column against the scale in the figure, is 25°C. (iii) Based on the scale shown (with marks at every 5°C divided further into 5 small divisions), the smallest value this thermometer can measure is 1°C.
Q9. A laboratory thermometer is not used to measure our body temperature. Give a reason.
Answer:
A laboratory thermometer is not used to measure body temperature mainly because its range (typically –10°C to 110°C) is far wider than needed for the human body, making it less precise for the narrow range of body temperatures (35°C to 42°C); also, it is not designed for safe, hygienic, or convenient contact with the human body the way a clinical thermometer is, and it can be inconvenient and less accurate for this specific, sensitive purpose.
Q10. 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 (Day One: 38.0, 37.8, 38.0, 38.0, 40.0, 39.0°C at 7am–10pm; Day Two: 38.6, 38.8, 39.0, 39.0, 39.0, 38.0°C; Day Three: 37.6, 37.4, 37.2, 37.0, 36.8, 36.6°C). (i) What was Vaishnavi's highest recorded temperature? (ii) On which day and at what time was Vaishnavi's highest temperature recorded? (iii) On which day did Vaishnavi's temperature return to normal?
Answer:
: (i) Vaishnavi's highest recorded temperature was 40.0°C. (ii) It was recorded on Day One at 7pm. (iii) Her temperature returned to normal (around 37.0°C or below) on Day Three, when the readings ranged from 37.6°C down to 36.6°C, close to or at the normal body temperature of 37.0°C.
Q11. If you have to measure the temperature 22.5°C, which of the following three thermometers will you use (Fig. 7.9)? Explain. 
Answer:
Among the three thermometers shown, with different smallest divisions, the one whose smallest division is 0.5°C (or smaller, i.e., finer) should be used, since only such a thermometer can precisely show a reading exactly at the halfway point of 22.5°C. A thermometer with a smallest division of 1°C can only show whole-degree readings and cannot accurately display the 0.5°C part of 22.5°C, so it would not be suitable.
Q12. 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:
(ii) 27.5°C
Q12. A laboratory thermometer has 50 divisions between 0°C and 100°C. What does each division of this thermometer measure?
Answer:
Each division measures 100°C ÷ 50 = 2°C.
Q13. 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.
Answer:
This is a drawing task. The student should draw a straight vertical or horizontal line representing the thermometer scale from 10°C to 20°C, marking major graduations at every whole degree (10, 11, 12 ... 20°C) and one smaller division exactly halfway between each pair of consecutive whole-degree marks, so that each small division represents 0.5°C (for example, a mark between 10°C and 11°C representing 10.5°C, and so on for each interval up to 20°C).
Q14. 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. This is because the normal human body temperature on the Celsius scale is only 37.0°C, so a reading of 101 on the Celsius scale would be impossibly high and dangerous (far above the range of 35°C to 42°C that human body temperature normally stays within). On the Fahrenheit scale, however, normal body temperature is 98.6°F, so 101°F represents a mild fever, which is a realistic and sensible reading.