Topic outline

    • Temperature

      Till now we have learned various types of measurement such length, weight, capacity and time. But none of these measurements can be used to find how hot or cold any object is.

      When we touch any hot or cold object, we can make out which is hot and which is cold. But the question here is how much cold or how much hot. At the same time, it is difficult to know the exact level of hotness or coldness by touch because the sense of touch varies from one person to another. To find exact answer, we need some measure of hotness or coldness.

      Temperature is the measure of the hotness or coldness of an object with reference to some standard value. The instrument which measures the temperature of body is known as thermometer.


      Each thermometer has a scale. Two different temperature scales that are commonly used are:

      1. The Fahrenheit Scale

      The Fahrenheit scale is marked from 32° F to 212° F. 32° F indicates the freezing point of water and 212° F indicates the boiling point of water.

      2. The Celsius Scale

      Celsius scale is also called centigrade scale and is marked from 0° C to 100° C. 0° C indicates the freezing point of water and 100° C indicates the boiling point of water.


      Comparison of two scales

      Conversion of Temperature

      When the temperature is given in degree Celsius:

      Step 1: Multiply the given temperature in degree by 9

      Step 2: Divide the product obtained by 5.

      Step 3: Add 32 to the quotient obtained in step 2 to get the temperature in degree Fahrenheit.

      Example: 55° C

      Here given temperature is 55° C.

      To convert into degree Fahrenheit first multiply 55 by 9 and we get product as 495.

      Then, divide 495 by 5 and answer we get is 99.

      Now, add 32 to 99 and final answer we get is 131.

      Therefore, 55° C = 131° F


      When the temperature is given in degree Fahrenheit:

      Step 1: Subtract 32 from the given temperature in degree

      Step 2: Multiply the difference obtained from step 1 by 5.

      Step 3: Divide the product obtained from step 2 by 9 to get the temperature in degree Celsius.

      Example: 90° F

      Here given temperature is 90° F.

      To convert into degree Celsius first we need to subtract 32 from 90 and we get 58.

      Then, multiply 58 by 5 we get answer as 290.

      Now divide 290 by 9 and we get answer as 32.2.

      Therefore, 90° F = 32.2° C


      Conversion Rule



      C = (F – 32) X 5/9

      F = 9/5 X C + 32


      Clinical Thermometer

      A medical thermometer, also known as a clinical thermometer is a thermometer used to measure body temperature. Most of these thermometers have both the two scales, Celsius scale and Fahrenheit scale. The scale runs from 35 degree Celsius to 42 degree Celsius.

      The temperature of a healthy human body is approximately 37 °C or 98.6 °F. The tip of the thermometer is inserted into the mouth under the tongue or under the armpit for a minute. Then, the number against the point at which the mercury column stops rising further indicates the body temperature of the person.


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