Temperature and its Measurement

Correct option: (ii) 37.0 °C

The normal body temperature of a healthy human adult is taken to be 37.0 °C (which is equal to 98.6 °F on the Fahrenheit scale). 98.6 °C would be dangerously high, and 32.0 °C or 27.0 °C are far below normal body temperature.

Correct option: (iv) 98.6 °F

Given: Temperature $= 37^\circ\text{C}$

Formula used:
$$^\circ\text{F} = \frac{9}{5} \times {^\circ\text{C}} + 32$$

Calculation:
$$^\circ\text{F} = \frac{9}{5} \times 37 + 32 = \frac{333}{5} + 32 = 66.6 + 32 = 98.6^\circ\text{F}$$

Answer: $37^\circ\text{C} = 98.6^\circ\text{F}$

(i) The hotness or coldness of a system is determined by its temperature.

*Explanation:* Temperature is the physical quantity that tells us how hot or cold a body or system is.

(ii) The temperature of ice-cold water cannot be measured by a clinical thermometer.

*Explanation:* A clinical thermometer has a limited range (typically $35^\circ\text{C}$ to $42^\circ\text{C}$), which is designed only for measuring human body temperature. Ice-cold water is around $0^\circ\text{C}$, which is far below this range.

(iii) The unit of temperature is degree Celsius (or degree Fahrenheit / kelvin, depending on the scale used).

*Explanation:* The most commonly used unit in everyday life is degree Celsius ($^\circ\text{C}$). The SI unit of temperature is kelvin (K).

**Correct option: (ii) $-10^\circ\text{C}$ to $110^\circ\text{C}$**

A laboratory thermometer is designed to measure a wide range of temperatures in experiments. Its typical range is from $-10^\circ\text{C}$ to $110^\circ\text{C}$. The range $35^\circ\text{C}$–$42^\circ\text{C}$ belongs to a clinical thermometer, while $32^\circ\text{C}$–$45^\circ\text{C}$ is too narrow for laboratory use.

Correct option: (ii) Student 2

Reasoning: The correct way to measure temperature using a laboratory thermometer requires:
1. The thermometer must be held vertically (not tilted).
2. The bulb must be immersed in the liquid but must not touch the bottom or sides of the beaker.
3. The temperature must be read while the thermometer is still immersed in the liquid.
4. The eye must be directly in line (horizontal) with the level of the liquid column.

Student 2 follows all these precautions correctly. The other students either tilt the thermometer, remove it from water before reading, or read it at an incorrect angle.

Note: This is a drawing/colouring activity. Since the specific temperature values written below Fig. 7.7 are not fully visible in the OCR text, the general method is described below.

Method to shade the thermometer column:
1. Identify the temperature value given (e.g., $37^\circ\text{C}$, $0^\circ\text{C}$, $100^\circ\text{C}$, etc.).
2. Locate that value on the Celsius scale marked on the thermometer drawing.
3. Colour (shade in red) the column from the bottom of the bulb up to the mark corresponding to the given temperature.

Example: If the temperature is $37^\circ\text{C}$, shade the column from the bulb up to the $37^\circ\text{C}$ mark on the scale.

*(Note: The figure shows a clinical thermometer based on the scale markings visible in the OCR context — range approximately 35 °C to 42 °C.)*

(i) Type of thermometer:
It is a clinical thermometer.

*Reason:* The scale range (approximately $35^\circ\text{C}$ to $42^\circ\text{C}$) is characteristic of a clinical thermometer used to measure human body temperature.

(ii) Reading of the thermometer:
Based on the figure, the reading is approximately **$37.0^\circ\text{C}$ (the exact value depends on where the liquid column ends in Fig. 7.8; students should read the value where the top of the liquid column aligns with the scale).

(iii) Smallest value this thermometer can measure:

Given:** The two bigger marks are $1^\circ\text{C}$ apart, and there are typically 10 small divisions between them.

$$\text{Smallest division} = \frac{1^\circ\text{C}}{10} = 0.1^\circ\text{C}$$

The smallest value that this thermometer can measure is $\mathbf{0.1^\circ\text{C}}$.