Introductory Concepts, Page 4

Heat:

 Heat is the SUM of the kinetic energy of the particles in a given sample of matter. Temperature is determined as the average kinetic energy of all the particles in a system. If the total heat content of the particles in a system is divided by the total number of particles in the system, the result is the average kinetic energy, which would determine the temperature. Two different systems can have the same heat content if their total kinetic energy values are the same. But, the system with the larger number of particles will have a lower average kinetic energy, or a lower temperature. Consider this example:

  • System A has 10000 particles: Total Kinetic Energy=50000 units
  • System B has 5000 particles: Total Kinetic Energy=50000 units
  • System A and System B contain the same amount of Heat, 50000 units.

BUT,

  • The average Kinetic Energy of System A is 5 units per particle.
  • The average Kinetic Energy of System B is 10 units per particle.
  • System B is at a higher temperature than System A, 10 units per particle> 5 units per particle.

Inertia:

 The resistance of an object to a change in velocity. There are two types of inertia.

  • Inertia of Motion--An object in motion will stay in straight-line motion until acted upon by an outside force.
  • Inertia of Rest--An object at rest will stay at rest until acted upon by an external force.

Inertia is dependent upon the mass of an object. Consequently, anything that has mass will have inertia.

  • If a bowling ball and a ping-pong ball were traveling in straight lines at the same velocity, it would be harder to stop the bowling ball or change its path. This is because it has a larger mass, and, thus, a greater Inertia of Motion.
  • If a bowling ball and a ping-pong ball were both standing still, it would be harder to make the bowling ball move. This is because it has a larger mass, and, thus, a greater Inertia of Rest.

It is useful to remember that even very small objects may be very hard to stop if they are moving at a very high velocity, or have a very high Inertia of Motion.

Isotopes:

  Isotopes are atoms of the same element that vary in the number of neutrons in their nuclei. They could be defined as atoms with the same atomic numbers but differing mass numbers, or atoms with the same numbers of protons but differing numbers of neutrons. See Nuclides.

 Isotopes will generally undergo the same chemical reactions, have the same chemical characteristics and physical characteristics. Isotopes will have differing nuclear qualities. Some isotopes of an element may be radioactive and others may be non-radioactive.

 

Isotope Mass:

 Isotope mass is the mass of the nucleus of a specific isotope of an element. It is an experimentally determined piece of information. When all the isotope masses of an element are averaged by taking into consideration their percentages of abundance, then the average will represent the atomic weight of the element.

Law of Conservation of Matter:

 The Law of Conservation of Mass says that matter can neither be created nor destroyed. In a chemical process, the total amount of mass present at the end of the process will equal the total amount that was initially present. This law is true for traditional reactions such as those done in a chemistry lab.

Consider the reaction between two substances, A and B, when they form the new substance C.

The Law of Conservation of Mass leads to the following statement for the relationship between A, B, and C.

 Questions and comments should be sent to :
   kdrews@bcpl.net  

Updated September 1, 2000