Temperature and its Measurement

Introduction: Temperature and its Measurement

The chapter begins with a real-life scenario involving two siblings, Lambok and his elder sister Phiban, who live in Shillong. One day, after returning from school, Lambok complains of feeling feverish. Phiban, concerned about his health, touches his forehead and suspects he might have a fever. To confirm this, she retrieves a thermometer from the almirah, cleans its tip with soap and water, and measures Lambok's temperature. Finding it normal, she advises him to change his uniform, eat lunch, and rest. This scenario introduces the importance of measuring temperature accurately rather than relying solely on subjective feelings or touch. It raises the question: Can we always correctly judge if a person has a fever just by touching? This sets the stage for understanding the need for objective measurement of temperature using instruments like thermometers.

• Temperature measurement is essential for accurate health assessment.
• Subjective feeling of hotness or coldness may not be reliable.
• Thermometers provide an objective way to measure temperature.
• Proper hygiene is important while using a thermometer (cleaning the tip).
• 📌 Temperature: A measure of how hot or cold a body is.
• 📌 Thermometer: An instrument used to measure temperature.

7.1 Hot or Cold?

This section explores how humans perceive hotness or coldness through the sense of touch, which is subjective and can sometimes be misleading. For example, during summers, tap water feels hotter than cold water stored in an earthen pot or refrigerator. We often judge temperature by touching objects or substances. However, this sense is not always reliable. To investigate this, an activity is proposed where one dips the right hand in warm water and the left hand in ice-cold water for 1-2 minutes, then places both hands simultaneously in tap water. The right hand may feel the tap water as cool, while the left hand may feel it as warm, even though both hands are in the same water. This demonstrates that our sense of touch can give contradictory sensations depending on prior exposure, and hence cannot always be trusted to judge temperature accurately. Therefore, an objective measure of temperature is necessary.

• Sense of touch is subjective and can give different sensations for the same temperature.
• Temperature sensation depends on previous exposure (adaptation).
• We cannot always rely on touch to judge hotness or coldness correctly.
• An objective measurement scale is needed to compare temperatures.
• 📌 Subjective sensation: Personal feeling that may vary from person to person.
• 📌 Objective measurement: A measurement that is independent of personal feelings.