TEACHER:--Atoms in molecules and solids are held together by chemical bonds. Chemical bonds are electromagnetic in origin, but can be modeled well by tiny springs. Two atoms held together by a spring have an equilibrium position. If they are pushed closer together, they repel each other. If they are pulled farther apart, they attract each other. If they are displaced in any way from their equilibrium position and then released, they start vibrating about their equilibrium position.--

J. Ghitis:** Are you implying that solids are different to molecules? Atoms are not just "held together" by chemical bonds. The atoms change radically their individual properties when combined by means of chemical bonds, which are electromagnetic not in origin but in their physical properties. The bonds are by means of electrons in the outer shells of the combining atoms. Electrons, as their name implies, possess electromagnetic properties.
As for atomic vibrations, I have posited that heat is the manifestation of the outermost electrons' vibrations, which are microkinetic energy that might be called also 'micromomentum.' Buildings and cells possess material walls. Not so atoms, whose boundary, which I call 'microevent horizon,' is defined by the gravity and inertia fields of the nucleons. When atoms are in the ionized state when exposed to intense heating, the outermost electrons' vibrations in this plasma are the depositories of heat. The ionized atoms, even single-electron hydrogen, retain their boundaries. More intense applied heat will now affect inner electrons and then the nucleons, causing the ejection of progressibly higher-energy photons. **

T:--An atom can form different chemical bonds with a variety of other atoms. Different bonds are represented by springs with different spring constants. The stiffer the spring, the more work it takes to pull the atoms apart. If enough work is done, then the spring is stretched too much and it breaks, i.e., the chemical bond breaks.--

JG:** You mean effort, not work, that is, it takes more force to do the work capable of disengaging (moving apart) the atoms from the molecule they formed. This subject is too complex to be presented in simpe mechanistic models. **

T:--At room temperature all atoms in a solid vibrate about their equilibrium position. If work is done which increases their kinetic energy, the amplitude of the vibrations increase, and eventually the chemical bonds break. Most free atoms quickly form new bonds. If the new bonds are stronger, i.e. the new springs are stiffer, they do more work pulling the atom to their new equilibrium positions than was needed to break the old bonds. This work is converted into random kinetic energy, i.e. thermal energy. Thermal energy is released by a chemical reaction. The temperature increases.

JG:** At a constant temperature tolerated by most living organisms, all undisturbed atoms and molecules in a closed system reach an equilibrium position, which is static in solids. Their temperature (indicative of their heat content) is a measure of their heat content, i.e., of the microkinetic energy of their outermost electrons' vibrations. In fact, these energy can not be called heat until it does work, as when acting on a thermometer directly applied to measure the energy in standard degrees.
The word 'work' here is confusing. The whole paragraph hence should be, "Intense heating increases the kinetic energy of molecules to the point of dissociation into their component atoms." **

T:--To burn fuel, work must first be done to break the chemical bonds in the fuel. This work provides the activation energy, the energy needed to start the chemical reaction. The free atoms and molecules then bond with oxygen. The new bonds with the oxygen atoms are much stronger than the broken bonds. As the atoms form new bonds, they gain thermal energy. When you strike a match, you first do work against friction to break the chemical bonds in some of the fuel on the head. The free atoms and molecules now combine with oxygen from the air, forming stronger bonds and thus releasing thermal energy. The random kinetic energy of these fast molecules is transferred in collisions to neighboring atoms and molecules, breaking their bonds, etc.--

JG:** Oxygen is not just a bystander waiting to be used for combustion. It is also fuel, as shown when it combines with hydrogen which is also fuel. Thus, a combustion of any matter in air is a mutual chemical reaction. The activation energy acts on both components, being usualy applied heat obtained by any means. Once combustion starts, it liberates the thermal energy that will continue the "chain reaction." **

T:--When you bring two objects of different temperature together, energy will always be transferred from the hotter to the cooler object. The objects will exchange thermal energy, until thermal equilibrium is reached, i.e. until their temperatures are equal. We say that heat flows from the hotter to the cooler object. Heat is energy on the move.--

JG:** All energy is on the move, because otherwise it is only potential energy, examples being static electricity, a chemical that can react, an object that can fall, or a compressed spring.
Without moving, work cannot be done. Energy is not exchanged, but transferred by molecules. The microkinetic energy of atoms decreases as it excites the electrons of lesser energetic ones, until the intensities become equal, i.e., reach equilibrium. **

T:--Heat will always flow from a hotter to a cooler object, without an external agent doing work. A difference in temperature always results in heat flow. (The hotter object always does positive work on the cooler object, and the cooler object does negative work on the hotter one. Two objects of different temperature always interact.)--

JG:** Heat is not an object but a manifestation of vibrating objects (electrons) that as a consequence possess microkinetic energy --which is micromomentum. Thus, heat cannot "flow." The "work" done (by the hotter molecules) might be called 'microwork.' **