Chapter 7.1, 7.2
System: part of the universe chosen for study. It can be as large as all the oceans
on Earth or as small as the contents of a beaker.
Surroundings: part of the universe outside the system with which the system
• Open system: free exchanges energy and matter with its surroundings.
• Closed system: can exchange energy with its surroundings, but not matter.
• Isolated system: does not interact with its surroundings.
Energy: the capacity to do work.
Work: done when a force acts through a distance. Moving objects do work when
they slow down or are stopped.
Kinetic Energy: the energy of a moving object.
Potential energy: due to condition, position, or composition; it is an energy
associated with forces of attraction or repulsion between objects.
Thermal energy: kinetic energy associated with random molecular motion. When
the potential energy in the ball is converted to kinetic energy found in the ball, the
surface and the surrounding air. In general, thermal energy is proportional to the
temperature of a system. The more vigorous the motion of the molecules in the
system, the hotter the sample and the greater is its thermal energy. However, the
thermal energy of a system also depends on the number of particles present. A
small sample at a high temperature such as 75ºC may have less thermal energy
than a pool at 30ºC.
Heat: energy transferred between a system and its surroundings as a re