Heat overview

Physics> Heat Review

Heat is a measurable form of energy that can move from one object to another. Does not belong to the category of substances.

Learning challenge

• Understand the three modes of heat transfer.

Key points

• Warmth is an important point affecting all aspects of human existence. The principles were established by James Maxwell.
• The amount of heat transfer can be measured by calorimetry.
• There are three modes of heat transfer: conduction, convection, and radiation.

Terms

• Calorimetry is the science of measuring heat absorbed or released during a chemical reaction or change of state.
• Heat transfer – the transfer of heat energy by conduction, convection or radiation.

Heat and heat transfer

Energy can take different forms and heat is one of the most interesting. It is often hidden, as it occurs only during transit and is transported by various methods. Heat transfer is present in every aspect of our existence and helps to understand how the universe works. That is why on a clear night we feel cool, and the earth’s core is still not cold.

(a) – Refreshing coolness on a clear night occurs due to wind and radiative heat transfer in cold outer space. (b) – The age of our planet has been debated for a very long time, but now we know that the mark is fixed at 4.5 billion years. The main focus of the debate was on the molten interior. But, if the Earth is so ancient, then its center should have cooled down long ago. The answer to the riddle was given by radioactivity found in rocks. It is this energy source that supports the internal melting of the planet, although heat is transferred to the surface.

Definition

In 1871, James Maxwell developed the Theory of Heat, where he raised the idea that there is a connection between heat and moving matter. For the first time, Benjamin Thompson spoke about this back in 1798. But it was Maxwell who created 4 conditions for identifying heat:

• It can be transferred from one object to another.
• It is a measurable quantity, therefore, amenable to mathematical calculations.
• It is not considered a substance, because it can be transformed into something (into mechanical work).
• This is one of the energetic forms.

Quantification of heat

The amount of heat transferred can be calculated by calculating with other quantities. Direct metering is possible with calorimetry and is the main empirical basis for the thermal quantity idea. The transferred heat is calculated by tracking changes in the properties of an object, such as an increase in temperature, volume, or a change in state. Indirect estimates are based on the law of conservation of energy (in some cases, the first law of thermodynamics).

Heat transfer methods

There are a lot of processes associated with heat transfer, so it is difficult to even imagine a situation when it does not occur at all. There are three ways to transfer heat:

• Physical contact (matter is stable on a macroscopic scale – there is thermal movement of atoms and molecules at any temperature index exceeding absolute zero). An example of conductivity would be the transfer of heat from a stove to a saucepan.
• Convection is the transportation of a liquid by macroscopic movement.
• Transportation by radiation. This is the radiation or absorption of microwaves, infrared radiation, visible light, or any other form of electromagnetic rays.

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