Definition of Temperature
The measurement of warmness or coldness of a substance is known as its Temperature.
SI unit of temperature is kelvin. Celsius and Fahrenheit are the other units used. Celsius is called as Centigrade as well.
It determines the direction of flow of heat when two bodies are placed in contact.
Activity 2: The Temperature of Boiling Water
Take water in a vessel and place the vessel on a stove. Fix the thermometer as shown in figure (Caution: The thermometer should not touch the vessel in which the water is being heated. Otherwise the thermometer will be broken at high temperature.)
All students have to read the temperature of the water and note the reading on the blackboard. Do you notice that the temperature is raising?
What is the temperature of water when it is boiling? 100°C
Does the temperature of the boiling water rise further after that? The temperature of boiling water does not increase. It keeps boiling at 100° C.
When boiling water is heated for some time, the water continues to receive more heat, but it's temperature does not rise further. The point at which the water boils and temperature becomes stable is called the boiling point of water.
Guess and Write:
(Check your assumption with the help of a thermometer.)
* Approximate temperature of the tea when you drink 60°C
* Approximate temperature of cool lemon juice when you drink 10°C
Normally, the room temperature of water is approximately 30oC. When we heat water, its temperature raises and it boils at 100oC. If we cool the water, it freezes at 0oC.
( Note : you have to say 30ºC as 30 degree celsius or 30 degree centigrade)
Is Neela correct?
Beaker A and B has water at 80o C.
Then pour the water of A and B to an empty beaker C. Now, What is the temperature of the water in the beaker C? Neela says it will be 160oC.
80oC + 80oC = 160oC Am I right ?
What is your opinion? Does Neela say correctly? Make a guess and verify it experimentally.
160° C is wrong. Its 80°C. Volume changes but heat per volume don’t change.
One day in 1922, the air temperature was measured at 59ºC in the shade in Libya, Africa. The coldest temperature in the world was measured in the Antarctic continent. It was appromately 89ºC. The minus sign (–) is used when the temperature falls below the freezing point of water, which is 0ºC. If water becomes ice at 0ºC, you can imagine how cold 89°C would be. Our normal body temperature is 37ºC. Our body feels cool if the air temperature is around 15 to 20 degree Celsius.
Can you estimate the night temperature in your village or city during winter?