Is heat the same as temperature?
This is part of a series on common misconceptions.
Is this true or false?
Temperature is the same as heat contained.
Why some people say it's true: When there is more heat, the temperature is higher.
Why some people say it's false: A smaller object takes lesser heat energy to be heated up.
The statement is \( \color{red}{\textbf{false}}\).
Explanation:
This statement is confusing, as the concepts of heat and temperature appear identical. In actuality, they represent very different physical phenomenon. HEAT is the form of energy which travels from one object to another. TEMPERATURE is a measure of the degree of hotness and coldness. Heat energy travels from the object at a higher temperature to the object at a lower temperature.
To delve deeper, let's consider the specific case of an ideal gas. First, let us see what temperature depends upon. In an ideal gas, the temperature affects the internal energy of the gas. Ideal gas molecules can possess energy through motion, and thus the internal energy depends on the kinetic energy (the energy of motion). Therefore, the temperature of an ideal gas depends on the kinetic energy of molecules:
\[\begin{align} \text{(Kinetic Energy)}&= \frac{f}{2}nRT\\ T &= \frac{2}{{fnR}}\text{(Kinetic Energy)}, \end{align}\] where \(f\) is the degree of freedom, \(n\) is the number of molecules, \(R\) is the gas constant, and \(T\) is temperature.The question that appears here is why heat energy travels from higher temperature to lower temperature? From the above analysis, it can be said that higher temperature implies greater kinetic energy of the molecules and they move with greater average speed. When an object with greater temperature is placed in contact with an object at a lower temperature, the molecules of the object at higher temperature are more energetic and they collide and pass their energy to the molecules of the object at a lower temperature. This transfer of energy from one body to another is called as heat transfer.
From the above analysis, it can be concluded that heat is a form of energy that is in transit and travels from higher temperature to lower temperature, whereas the temperature is a measure of the internal energy of the object.
Query: In the case of ideal gases, molecules can move to get kinetic energy. But in the case of solids, how can the molecules get the energy and temperature?
Reply: For solids, the molecules are not free to move. However, they can oscillate and vibrate about their respective fixed positions. Due to this motion, the molecules obtain energy which is proportional to the temperature of the solid.
Query: In the case of ideal gases, the collisions are perfectly elastic. How can the energy from one object be transferred to another object?
Reply: For elastic collisions, the total kinetic energy remains conserved, but energy can be transferred from one object to another. Thus, when fast moving molecules of one object collide with slow moving molecules of another object, this results in a transfer of energy from the former to the latter. Due to this process, the hotter object cools down and the colder object heats up.
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