Heat as a Basis of Thermal Physics

In physics, the word heat brings to our minds a feeling of hotness, for instance the type of feeling we experience during a cloudless harmattan afternoon or during vigorous exercises. Apart from making us feel uncomfortable during afternoon, heat makes more comfortable during a cold harmattan morning.

In general, heat serves man in various ways, in cooking, drying clothes, warming our homes. In industries, heat is used in extraction of metals from their ores, for shaping, softing, cutting, hardening, coating of metals and lot more.

Definition

Heat is the form of kinetic energy which cause a rise in temperature in a body as it is absorbed or a reduction in temperature as it is lost to the environment.

Heat physics is an essential aspect of physics. Since is applied in various aspect (field) of physics as a course of study. For instance, if a block of heat copper is placed in a beaker containing cold water we know from experience that the block of copper cools down and the water warms up until they come to equality of temperature. What causes this decrease in the temperature of the copper block and the increase in the temperature of water?. We say that this was caused by the fact that (heat) energy was transfer from the copper block to the water.

Heat is a form of energy that is transferred across a boundary by virtue of a temperature difference or temperature gradient. (Adapted from). Thermodynamics Gordon J (1959).

Implied in this definition is the very important fact that a body dose not contains heat, but that heat is transient phenomenon.

If we consider the hot block of copper as one system and the (cold) water

In the beaker s another system. When the copper is placed in the water and the two are in thermal communication, heat is transferred from the copper to the water until equilibrium of temperature is established. At that point we no longer have heat transfer, since there is no temperature difference. If follows that heat is identified at the boundaries of the system, hence heat is defined as energy being transferred across the system boundary.

Other definition has it as follows

(a) Heat is a measure of the total internal energy of a body. (b) Heat defined as energy in transit (motion).

(c) Heat is a form of energy possessed by a substance by virtue of the vibration movement, i.e. kinetic energy of its molecules or atoms.

The significance and common factors in these definitions is that,

1. A form of energy
2. A measure or internal energy
3. Energy in motion (transit)
4. Energy of a body as a result of the vibration movement of its molecules

Heat is measured in joule J after the scientist who worked on heat other units as the BTU (British thermal units) have been in place but the generally accepted unit is the joule (J) or calories. For instance one BTU is equivalent to 252 calories

Definition of Relevant Terms in Thermal Physics

1. The study of heat energy for effectiveness, there must be absolute consideration of relevant terms in thermal (heat) physics. Some are as follows
2. Meat flow: this represent the movement of thermal energy from place to place
3. Thermal conductively: this is the property of material related to its ability to transfer heat through itself
4. Heat transfer rate: this is the quantity of heat energy flowing per unit of tie through an object
5. Temperature: this is the amount of their(heat) thermal energy available. It is measured in celcius or Kevin scale.
6. Conductors: these are materials which allow the passage of heat and electricity
7. Thermodynamics: this is the terms used to designate the science of relational between heat and power. It is concerned with the amount of heat transfer as a system undergoes a process from one equilibrium state to another

Historical Background

Heat has always been perceived to be something's that produces in us a sensation of warmth and one would think that the nature of heat is one of the first things understood by mankind. But it was only in the middle of the nineteenth century that we had a true physical understanding of the nature of heat, this owed to the development at that time of the kinetic theory, which creates molecules as my balls that are in motion and thus posses kinetic energy.

Heat is then defined as the energy associated with the random motion of atoms and molecules. Although it was suggested in the eighteenth centuries that heat is the manifestation of motion at the molecules level (called the live for a), the prevailing view of heat until the middle of the nineteenth century was based on the calorie theory proposed by the French chemist Antoine Lavoisier (1743-1794)

In 1789. The calorie theory asserts that heat is a fluid like substance called the caloric that is a mass less, colorless, odourless and tasteless substance that can be poured from one body into another. When calorie was added to a body, its temperature increased, and when caloric was removed from a body, its temperature decreased. When a body could not contain any more caloric, much the same was as when a glass of water could not dissolved any more salt or sugar, the body was said to be saturated with caloric. This interpretation give rise to saturated liquid and vapour which are still in date to day.