TEMPERATURE

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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.

Scales

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

How were these formulas developed? They came from comparing the two scales. Since the freezing point is 0° in the Celsius scale and 32° on the Fahrenheit scale, we subtract 32 when converting from Fahrenheit to Celsius, and add 32 when converting from Celsius to Fahrenheit.

 

There is a reason for the fractions  and , also. There are 100 degrees between the freezing (0°) and boiling points (100°) of water on the Celsius scale and 180 degrees between the similar points (32° and 212°) on the Fahrenheit scale. Writing these two scales as a ratio, , gives . If you flip the ratio to be , you get . Notice how these fractions are used in the conversion formulas.

 

The example below illustrates the conversion of Celsius temperature to Fahrenheit temperature, using the boiling point of water, which is 100° C.

 

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.

To convert a Celsius measurement to a Fahrenheit measurement, use this formula.

 

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.

To convert a Fahrenheit measurement to a Celsius measurement, use this formula.

 

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

 

Word Problem

Example 1: Our friends in Boston would like to know what a Vancouver temperature of 15^o C is in degrees Fahrenheit.

From F = 1.8C + 32 let C = 15. Then, F = 1.8(15) + 32 = 59. Thus, in Boston we have 72^o F while in Vancouver it’s 59^o F. Big difference! 72 – 59 = 13 degrees.

Example 2: Our friends in Vancouver would like to know what the Boston temperature of 72^o F is in Celsius.

So, C = (F – 32)/1.8 = (72 – 32)/1.8 ≅ 22.

Boston is at 22^o C while Vancouver is at 15^o C. Only a 7^o C change. The difference in temperature sounds better in degrees Celsius.

Example 3: The measured temperature in Death Valley is currently 35^o C. What is this temperature in degrees Fahrenheit?

In degrees Fahrenheit this is F = 1.8C + 32 = 1.8(35) + 32 = 95.

Not bad, 95^o F. However, on July 10, 1913, the hottest temperature ever recorded in the world was in Death Valley. This temperature was 134^o F.

Example 4: Our friends in Canada can’t relate to this 134^o F. Let’s convert to degrees Celsius.

C = (F – 32)/1.8 = (134 – 32)/1.8 ≅ 57^o C. More than half way up the Celsius scale from freezing towards boiling. No wonder it’s called Death Valley.

 

Quiz

1. Convert the following temperatures into Celsius scale: a. 80°F b. 105°F c. 44°F
2. Convert the following temperatures into Fahrenheit scale: a. 65°C b. 20°C c. 82°C
3. One day the maximum temperature in the month of June in Delhi was recorded as 45° C. What was the temperature in degree Fahrenheit of Delhi on that day?
4. What is the freezing and boiling point of water in degree Celsius?
5. Which instrument in used to measure hotness or coldness of an object?

Ria is having 103°F temperature. She took some medicine and temperature dropped by 2°F. What is her temperature now in °C?

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