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Chapter 10: Problem 2

In what two ways can the internal energy of a system be increased?

Short Answer

Expert verified
The internal energy of a system can be increased in two ways: by heat being added to the system and by work being done on the system. The heat increases the system's energy by causing the molecules to move more rapidly, leading to an increase in kinetic energy, and possibly, in potential energy, if a change in the physical state occurs. Work increases the system's energy by causing an increase in the kinetic energy of the system's particles, due to the work input. Both ways result in increased internal energy.

Step by step solution

01

Understanding Internal Energy

The internal energy of a system in relation to thermodynamics is the total energy contained within the system. This includes kinetic energy and the potential energy of particles in the system. It also encompasses more complex forms of energy such as molecular rotation and vibration.
02

Increasing Internal Energy Through Heat

Heat is a form of energy. When it is added to a system, it increases the system's internal energy. This is because heat causes the molecules within a system to move more rapidly, leading to an increase in kinetic energy, which is a part of internal energy. Also, heat can cause changes in the physical state, such as melting or evaporation, which are characterized by an increase in the potential energy, also part of internal energy. Therefore, heat increases the system's internal energy.
03

Increasing Internal Energy Through Work

Work can also increase a system's internal energy. When work is done on a system, for instance compressing a gas, the kinetic energy of the particles in the system increases. This increase in kinetic energy leads to an increase in the system's internal energy.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Internal Energy
In simple terms, internal energy is the total amount of energy inside a system. This energy is made up of both kinetic energy, which is the energy of the motion of particles, and potential energy, which is the energy stored within the system. Think of internal energy as a giant bank of energy reserves. These reserves can be accessed by the particles within the system鈥攍ike a savings account for molecular movement and interactions. Internal energy also includes microscopic energies such as rotational and vibrational energy of molecules that contribute to the overall energy state of the system.
Heat Transfer
Heat transfer is an effective method by which internal energy can be increased. When we add heat to a system, we're essentially transferring energy to the system's particles. This additional energy allows the particles to move faster, boosting their kinetic energy.
  • When a substance is heated, its molecules vibrate, rotate, or move faster.
  • The increase in kinetic energy leads to an increase in internal energy.
  • Occasionally, heat can cause a substance to change state鈥攍ike ice melting to water, increasing potential energy in the process.
This process highlights how heat transfer directly impacts the internal energy of a system by increasing both kinetic and potential energy.
Work
In addition to heat, work is another way to increase a system's internal energy. Imagine pushing a piston to compress a gas. This action requires energy, which is transferred to the system and increases its internal energy.
  • When work is done on a system, the external force changes the system's state.
  • This often involves changing the pressure or volume, as in the case of compressing gas within a cylinder.
  • The increased compression raises the kinetic energy of the particles since they are forced closer together and move more vigorously.
Thus, work, like heat transfer, can increase the internal energy by boosting kinetic energy.
Kinetic Energy
Kinetic energy is the energy of motion. In thermal contexts, it refers to the energy of particles moving within a system. The faster particles move, the higher the kinetic energy.
  • Kinetic energy is a crucial part of internal energy, influencing temperature.
  • When heat is added to a system, particle movement increases, raising kinetic energy.
  • Elevated kinetic energy often means higher temperatures and potentially changing states of matter.
This concept is key in thermodynamics as it dictates how substances respond to changes in energy.
Potential Energy
Potential energy in thermodynamics represents stored energy. This energy is sometimes a result of the positions or arrangements of particles within the system. It can increase during phase changes, like when solids melt into liquids or liquids vaporize into gases.
  • Potential energy is latent energy, waiting to be converted into kinetic energy or work.
  • Phase changes involve potential energy shifts, as energy is needed to rearrange molecules.
  • Despite not involving movement, potential energy is essential as it contributes to internal energy.
Understanding potential energy's role helps explain energy changes without directly altering temperature.

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Most popular questions from this chapter

Define a thermodynamic system and its environment.

What conditions are necessary for a heat engine to have an efficiency of \(1.0 ?\)

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A gas expands when 606 J of energy is added to it as heat. The expanding gas does 418 J of work on its surroundings. a. What is the overall change in the internal energy of the gas? b. If the work done by the gas were equal to \(1212 \mathrm{J} \text { (rather than } 418 \mathrm{J}),\) how much energy would need to be added as heat in order for the change in internal energy to equal the change in internal energy in part a?

Suppose the waste heat at a power plant is exhausted to a pond of water. Could the efficiency of the plant be increased by refrigerating the water in the pond?
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