Internal Energy Formula

The energy accumulated inside a system as a result of the particles’ random movements and the potential energy contained in the components as a result of their alignment is called internal energy. We are all familiar with the universal law of conservation of energy. Chemical reactions are incapable of generating or demolishing any energy, but can conveniently transform it from one form to another. Internal energy is the energy contained inside a system, which comprises the kinetic energy of molecules as well as the energy held in the chemical bonds between them.

Random motion generates energy in a variety of forms, including relativistic, circular, and kinematic energy. We use the letter U to denote it. As a result, we may argue that internal energy is a state function and that all internal energy processes from one state to the next will be the same.

Formula

ΔU = q + w

where, 

• ΔU denotes the change in internal energy
• q denotes the heat
• w denotes the effort expanded

Sample Questions

Question 1. Enlist some factors that impact internal energy.

Answer:

Internal energy may be changed by changing the temperature or volume of an item without changing the number of particles inside the body. Temperature: As the temperature of a system rises, the molecules move faster, resulting in greater kinetic energy and consequently an increase in internal energy.

Question 2. Find the change in internal energy of a system at 23 J of heat and 566 J of work done.

Answer:

q = 62 J 

w = 566 J

Since, ΔU = q + w

= 62 J + 566 J

= 628 J

Question 3. What would be the work done in a system if its volume is constant?

Answer:

Reactions or processes can sometimes take place in a hard, sealed container, such as a bomb calorimeter. Now, since ΔV=0, it is impossible for gases to accomplish work when there is no change in volume. As a result, the effort expanded or the work done in the system equals zero.

Question 4. How can you say that internal energy is a state function?

Answer:

Internal energy of a system numerically characterizes the stable state of a system at equilibrium, independent of how and why the system got there. Hence, it defines the system as a whole, and is, therefore, a state function.

Question 5. Find the change in internal energy of a system at 68 J of heat and 33 J of work done.

Answer:

q = 68 J

w = 33 J

Since, ΔU = q + w

= 68 J + 33 J

= 101 J