Heat Was Thought to Be a Fluid

The ability to flow is an aspect of conserved properties mass, momentum, and energy can all flow. What about heat When a hot object contacts a cold one, heat flows. Does it follow that heat is a conserved quantity It does not. Heat is not a conserved quantity. All conserved properties can flow, but not all properties that flow are conserved. 

The view of heat as a fluid began to change in the mid-1700s. The first step was the concept of heat capacity, developed by J Black around 1760 he heated mercury and water over the same flame and discovered that the temperature of the mercury was higher than the temperature of the water. He concluded that calorique could not be a simple fluid, because the amount taken up depended on the material that contained it. Different materials have different capacities to take up heat. The heat capacity of a material was defined as the amount of heat required to raise its temperature by 1 °C. 

Other problems with the theory of calorique emerged at that time. First, it was shown that radiant heat could be transmitted through a vacuum by electromagnetic radiation. If heat is a form of matter, hov could it pass through a vacuum that is devoid of matter  

The First Law of Thermodynamics the Conservation of Heat Plus Work 

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The heat capacity of a sohd quantihes the relationship between the temperature of a body and the energy supplied to it. The ideas date from times when heat was thought to be a fluid that could be transferred from one object to another. If a large amount of heat (energy) supplied to a body produced only a small temperature increase, the sohd was said to have a large heat capacity. The heat capacity of a material is defined as ... 

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