# All Science Fair Projects

## Science Fair Project Encyclopedia for Schools!

 Search    Browse    Forum  Coach    Links    Editor    Help    Tell-a-Friend    Encyclopedia    Dictionary

# Science Fair Project Encyclopedia

For information on any area of science that interests you,
enter a keyword (eg. scientific method, molecule, cloud, carbohydrate etc.).
Or else, you can start by choosing any of the categories below.

# Internal energy

The internal energy of a system (abbreviated E or U) is the total kinetic energy due to the motion of molecules (translational, rotational, vibrational) and the total potential energy associated with the vibrational and electric energy of atoms within molecules. Internal energy is a quantifiable state function of a system. The SI unit of internal energy is the same as for energy, and is the joule.

For systems consisting of molecules, the internal energy is partitioned among all of these types of motion. In systems consisting of monatomic particles, such as helium gas and other noble gases, the internal energy consists only of the translational kinetic energy of the individual atoms. Monatomic particles, of course, do not rotate or vibrate, and are not excited to higher electrical energies, except at very high temperatures.

Each molecular energy state has its own internal energy.

## Measurement

Internal energy can not be measured directly; it is only measured as a change (ΔU). The equation for change in internal energy is

$\Delta U = Q \pm W \,\!$

where

Q is heat input to or output of the system, measured in joules
W is work done on or by the system, measured in joules

A positive value of W represents work done on the system, a negative value representing work done by the system. A positive value of Q represents heat flow into the system, a negative value representing heat flow out of the system.

## Duhem-Gibbs Relation

For quasistatic processes, the following relation holds:

$\Delta U = T \Delta S - p \Delta V + \mu \Delta N \,\!$

where

T is the temperature, measured in kelvins
S the entropy, measured in joules / kelvin
p the pressure, measured in pascals
V the volume, messured in cubic metres.
μ the chemical potential, (measured in joules / mole (?)
N the number of particles in the system, (measured in moles ?)
Δ denotes the differential, the instantaneous change.

## See also

03-10-2013 05:06:04
The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details
Science kits, science lessons, science toys, maths toys, hobby kits, science games and books - these are some of many products that can help give your kid an edge in their science fair projects, and develop a tremendous interest in the study of science. When shopping for a science kit or other supplies, make sure that you carefully review the features and quality of the products. Compare prices by going to several online stores. Read product reviews online or refer to magazines.

Start by looking for your science kit review or science toy review. Compare prices but remember, Price \$ is not everything. Quality does matter.
 Science Fair Coach What do science fair judges look out for? ScienceHound Science Fair Projects for students of all ages
 All Science Fair Projects.com Site All Science Fair Projects Homepage Search | Browse | Links | From-our-Editor | Books | Help | Contact | Privacy | Disclaimer | Copyright Notice