Core physics concepts of this study are: thermal energy, heat and temperature. Such concepts involve many difficulties that often are connected with different definitions in textbooks. For this reason we, here, clarify the main definitions of the involved concepts.

In the Unit we discuss about Thermal Energy arising from the fact that particles of matter are in constant motion and that this motion relates directly to the state of matter of the object (solids, liquids, or gases). Temperature affects how fast these particles move. The higher the temperature the faster the particles move. Moving particles possess kinetic energy.

Temperature is defined as a measure of  the average kinetic energy of the particles of an object.

Thermal Energy is the total sum of all the energies of the object  particles. As a consequence,  thermal energy and temperature are related though different: temperature is proportional to the average kinetic energy of the particles; thermal energy is the total amount of the kinetic energy of the object particles.Transfer of thermal energy between systems can happen through three different  processes:

Conduction – direct contact

Convection – through a fluid

The term heat involves the quantity of energy transferred from one place in a body or thermodynamic system to another place, or beyond the boundary of one system to another one due to thermal contact when the systems are at different temperatures. In this description, it is an energy transfer to the body in any other way than the mechanical work performed on the body.

Transfer by conduction is the transfer of thermal energy between regions of matter due to a temperature gradient. Heat spontaneously flows from a region of higher temperature to a region of lower temperature, temperature differences approaching thermal equilibrium.

On a microscopic scale, conduction occurs as rapidly moving or vibrating atoms and molecules interact with neighboring particles, transferring some of their kinetic energy. Heat is transferred by conduction when adjacent atoms vibrate against one another, or as electrons move from one atom to another. Conduction is the most significant mean of heat transfer within a solid or between solid objects in thermal contact. Conduction is greater in solids because the network of relatively fixed spatial bounds between atoms helps to transfer energy between them by vibration.

Transfer by convection is the transfer of thermal energy through a substance by mean of currents of  fluids (liquids and gases).Transfer by radiation  is transfer by electromagnetic waves. These waves may pass through all matter states and also through the vacuum space by transferring energy called radiant energy.Transfer by conduction and convection involves a direct contact between bodies at different temperatures. In this case we say that heat is exchanged between the two bodies.

Transfer by radiation is transfer by electromagnetic waves. These waves may pass through all matter states and also through the vacuum space by transferring energy called radiant energy.

Transfer by conduction and convection involves a direct contact between bodies at different temperatures. In this case we say that heat is exchanged between the two bodies. Transfer by radiation involves interaction between one body and the electromagnetic radiation emitted by the other body.

• Differentiate between heat and temperature;

• Understand the concept of thermal equilibrium and thermal process;

• Differentiate among conduction, convection, and radiation;

• Give examples of how conduction, convection, and radiation are considered in choosing materials for buildings and designing an house model;

• Explain how environmental factors such as wind, solar radiation, and temperature affect the design of an house and the choice of the materials.