Difference between temperature and heat

Question

It is becoming very difficult for me to understand the difference between temperature and heat.

About heat all I have read :

1. Heat exchange is related to as exchange of matter + energy.

2. Heat is related as total kinetic energy of molecules. Translational + vibrational + rotational.

Now, I can kind of relate energy here. For exchange of matter, it’s like if put a ice cube (less kinetic energy ) into fire (high kinetic energy ). Then there is exchange of kinetic energy or both will try to make their kinetic energy equal by one reducing it and the other increasing it.

About temperature:

1. Temperature is related to as average kinetic energy of moles from the equipartition theorem.

Now, we know as temperature of room increases, heat of the room also increases.

I am not able to think or find any difference between the two.

Answer 1

In engineering terms heat (energy) and temperature are two different things.

One (of many) real life examples is the kitchen stove. When you turn on the kitchen, (and leave it at a set point), the kitchen will provide thermal energy (heat) at a constant rate. However if you put a pan onto the kitchen stove you will see that its temperature rises initially and then reaches a certain point.

In the above scenario, you see that thermal energy is accumulated into the frying pan. That accumulation causes the temperature to rise.

To wrap this up, in this context :

• Heat (or heat energy, or heat flux): is the thermal energy that moves from one system to another (or from one part of the system to another). In nature, heat flow from hotter to cooler parts.
• Temperature: is a measure of the thermal energy which is accumulated in a system. That thermal energy is "stored" as kinetic energy of the molecules in the system.

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Some differences between energy and heat

Quality	Heat	Temperature
Is it a type of energy	Yes	No
Does it describe the state of the system	No	yes
Does it transfer from one system to another	yes	No
Can it be measured absolutely	No	yes
Does it determine the rate of energy exchange	No	yes
Is it a system property	No	yes

Additionally, heat transfer can result (actually most of the times does) in temperature change (there are exceptions like phase change).

Answer 2

A little example:

• Water has a specific heat capacity (SHC) of 4.2 kJ.kg^-1.K^-1.
• I have a 2.1 kW electric kettle.
• $$ \Delta T = \frac {P \cdot t}{m \cdot SHC} $$ where $ \Delta T $ is the temperature rise, $P$ is power (kW), $t$ is time and $m$ is mass (kg).
• If I run the kettle for 60 s I will put $2.2 \times 60 = 132 \ \text{kJ} $ (energy) into the water.
• If I have 1 L of water the temperature rise will be $$ \Delta T = \frac {2.1 \cdot 60}{1 \cdot 4.2} = 30 ^\mathrm{o}\text C $$
• If I have 2 L of water the temperature rise will be $$ \Delta T = \frac {2.1 \cdot 60}{2 \cdot 4.2} = 15 ^\mathrm{o}\text C $$

You can see here that we have added the same amount of heat into both masses of water but have raised the temperature by different amounts because the additional heat is distributed through a greater mass in the larger volume of water and so the resultant temperature rise is lower.

Answer 3

Temperature is an intensity , heat is a quantity.

Answer 4

Keep adding heat to water when it is at 100 deg C causes a phase change but no more temperature change.