When a closed system receives energy as heat, this energy increases the internal energy. It is distributed between microscopic kinetic and microscopic potential energies. A second kind of mechanism of change in the internal energy of a closed system changed is in its doing of work on its surroundings.

The first law of thermodynamics states that the energy of the universe is constant. The change in the internal energy of a system is the sum of the heat transferred and the work done. The heat flow is equal to the change in the internal energy of the system plus the PV work done.

The Earth’s internal heat source provides the energy for our dynamic planet, supplying it with the driving force for plate-tectonic motion, and for on-going catastrophic events such as earthquakes and volcanic eruptions.

The internal energy is the total amount of kinetic energy and potential energy of all the particles in the system. When energy is given to raise the temperature , particles speed up and gain kinetic energy.

Pressure and volume change while the temperature remains constant. Since no work or heat are exchanged with the surrounding, the internal energy will not change during this process. Thus, the internal energy of an ideal gas is only a function of its temperature.

“Change in internal energy is zero if temperature is constant because, internal energy is a function of temperature only.” Well, this is what I read everytime I study thermodynamics. But, in this process, the temperature remains constant. If temperature is constant, change in internal energy should be zero.

Energy is an extensive quantity that does depend on the amount of matter involved. The temperature of an object depends on the state of motion of its particles: the higher the temperature, the faster moving are the particles (the number of particles does not matter).

Joule’s law

If we have an endothermic reaction heat is gained by the system and the sign of q is positive. Any work done by the system uses energy and the system loses energy, so the sign of w is negative….Internal Energy.

This energy flow is in the form of either heat or work. Therefore, we equate any change in the internal energy of a system with the sum of the heat and the work. So a negative change means the final energy is lower than the initial energy. w<0 is work out of the system.

The internal energy for a system is the total energy for that system (potential + kinetic). So a negative change means the final energy is lower than the initial energy.

The first law of thermodynamics states that the change in internal energy of a system equals the net heat transfer into the system minus the net work done by the system. In equation form, the first law of thermodynamics is ΔU = Q − W. Here ΔU is the change in internal energy U of the system.

Enthalpy: Enthalpy is the heat energy that is being absorbed or evolved during the progression of a chemical reaction. Internal Energy: Internal energy of a system is the sum of potential energy and kinetic energy of that system.

Some similarities are: 1) The more heat there is, the higher the temperature. 2) The less heat there is, the lower the temperature. 3) Mathematically the heat and the temperature difference between two points are proportional.