A microscopic approach to the internal energy in an ideal gas.
Differences and relations with temperature are emphasized.

The internal energy U of a system is defined as the sum of the energies of all the constituent particles. The internal energy of an ideal gas does only depend on the temperature and the number of particles, and not on the volume occupied by the gas. Let us carry out an experience to confirm this statement.

WARNING: before answering the questions make sure that the Test Control Window is open, if not click here.
EXPERIENCE: Relation between internal energy and volume occupied by a gas.

  • By clicking  the button 150 particles are obtained that occupy a part of the cube and with a certain energy. 
  • Place the wall at the end, at 100. 
  • Repeat the experience with different volumes. 
Considering the results of the previous experience choose one of the following options: 

Given two ideal gases with the same type and number of particles, and at the same temperature, 

The larger the volume - the lower the internal energy. 
The pressure is the same. 
The internal energy is independent of the volume. 
End the simulation.

An experience will be performed to help understanding the differences between the internal energy U and the temperature T of a system.
EXPERIENCE: Comparison between two systems.


Two systems are shown made up of particles of the same mass. With the "CONTROL PANEL" we can control the number of particles and the energy of each system, and therefore its temperature. 

If the systems possess the same internal energy U but different temperature T this is because 
They occupy the same volume.
The system with lower temperature has less particles.
The system with higher temperature has less particles.
To make equal the temperature of two systems with the same internal energy but different number of particles, 
Some particles are removed from the system with less particles.
The energy of the system with less particles is lowered.
The energy of the system with less particles is increased.

Check your conclusions byclicking here

Index 1.Introduction 2.Pressure 3.Temperature 5.Heat
6.Work 7.First Law 8.Entropy 9.Velocity Distribution 10.Specific Heat