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Temperature and its Measurement - Concepts of Hot and Cold

Grade 6CBSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Temperature is a reliable measure of the degree of hotness or coldness of an object.

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Our sense of touch is subjective and not a reliable way to measure the exact temperature of an object.

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A thermometer is the device used for measuring temperature. The standard unit of temperature used in India is degree Celsius (∘C^{\circ}C).

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A clinical thermometer is used to measure human body temperature. Its range is from 35∘C35^{\circ}C to 42∘C42^{\circ}C.

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The normal temperature of a healthy human body is approximately 37∘C37^{\circ}C.

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A clinical thermometer has a 'kink' (a constriction) near the bulb that prevents the mercury level from falling on its own when removed from the mouth.

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A laboratory thermometer is used to measure the temperature of objects other than the human body. Its range is generally from −10∘C-10^{\circ}C to 110∘C110^{\circ}C.

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While reading a laboratory thermometer, it must be kept upright and should be read while its bulb is still in contact with the substance.

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Digital thermometers are becoming popular as they do not contain toxic mercury and display the temperature as a digital value.

📐Formulae

Value of 1 small division=Difference between two bigger marksTotal number of small divisions between them\text{Value of 1 small division} = \frac{\text{Difference between two bigger marks}}{\text{Total number of small divisions between them}}

Normal Body Temperature=37∘C\text{Normal Body Temperature} = 37^{\circ}C

Clinical Thermometer Range=35∘C to 42∘C\text{Clinical Thermometer Range} = 35^{\circ}C \text{ to } 42^{\circ}C

Laboratory Thermometer Range=−10∘C to 110∘C\text{Laboratory Thermometer Range} = -10^{\circ}C \text{ to } 110^{\circ}C

💡Examples

Problem 1:

On a clinical thermometer, there are 1010 small divisions between the 37∘C37^{\circ}C and 38∘C38^{\circ}C marks. What is the value of one small division?

Solution:

The difference between the two bigger marks is 38∘C−37∘C=1∘C38^{\circ}C - 37^{\circ}C = 1^{\circ}C. The number of small divisions is 1010. Therefore, the value of one small division is 1∘C10=0.1∘C\frac{1^{\circ}C}{10} = 0.1^{\circ}C.

Explanation:

To find the smallest unit a thermometer can measure, we divide the temperature interval by the number of segments within that interval.

Problem 2:

Why does the mercury level not fall or rise in a clinical thermometer when taken out of the mouth, whereas it falls immediately in a laboratory thermometer?

Solution:

A clinical thermometer has a kink (constriction) which prevents the mercury from flowing back into the bulb immediately. A laboratory thermometer does not have a kink.

Explanation:

The kink is a physical barrier that allows us to read the body temperature accurately even after the thermometer is removed from the patient's mouth. Laboratory thermometers are designed to show instantaneous temperature changes while in contact with the material.