Chapter 6, Problem 6.1QP

Define these terms: system, surroundings, open system, closed system, isolated system, thermal energy, chemical energy, potential energy, kinetic energy, law of conservation of energy.

Interpretation Introduction

Interpretation:

The given terms have to be defined.

Explanation of Solution

System: System can be defined as portion of universe.  The physical and chemical changes of substance generally constitute a system.

There are types of system in thermodynamics namely,

1. 1. Open system
2. 2. Closed system
3. 3. Isolated system

Surroundings: Surrounding can be defined as rest of universe other than the system.

Consider, the example of acid-base neutralization reaction,

The reactants $\text{HCl}$ and $\text{NaOH}$ are called as system. The container and water in which the reactants are dissolved are called as surroundings.

Open system: The free exchange of matter and energy with its surroundings is called as open system.  The exchange of matter in open system takes place either by addition of matter or removal of matter.  The exchange of energy is much more complicated than exchange of heat.  The exchange of energy takes place through heat and through work.

Closed system: The exchange of energy with its surroundings and not matter is called as closed system.  The transfer of energy is similar to that of open system

Isolated system: Either exchange of energy or matter takes place with the surroundings is called isolated system.

Thermal energy: It can be defined as internal energy that is seen in the system because of its temperature.  Thermal energy deals the unsystematic motion of atoms and molecules.  Its type of kinetic energy that is due to motion.  Thermal energy results in substance possessing an internal temperature, which can be measured.

Chemical energy: Chemical energy can be defined as the energy that is seen in the chemical bonds of atoms and molecules.  The chemical energy occurs as energy released during a chemical reaction.

Examples of matter containing chemical energy are,

1. 1) Coal- Chemical energy is converted into light and heat.
2. 2) Wood- Chemical energy is converted into light and heat. etc

Potential energy: The energy possessed by an object due to its relative point to some other object, stress surrounded by itself, its electric charge or any other external factor is called as potential energy.

Potential energy can be calculated using the formula,

$\text{P}\text{.E=mgh}$

Where m= mass, g=gravity due to acceleration and h=height.

Kinetic energy: The work that is required to accelerate a body of a given weight from rest to its velocity is called kinetic energy.  The kinetic energy of object is calculated by the formula,

$\text{K}\text{.E=}\frac{\text{1}}{\text{2}}{\text{mv}}^{\text{2}}$

Where m= mass and v=velocity.

Law of conservation of energy: The first law of thermodynamics states that energy can be either destroyed or created but instead it can be converted from one form to other.  The first law of thermodynamics is modified version of law of conversion of energy for a thermodynamic system.  The total energy of system that is isolated is constant.

The equation for the first law of thermodynamics is given by,

${\text{U=U}}_{\text{f}}{\text{-U}}_{\text{i}}$

Where U=total energy of the system

${\text{U}}_{\text{f}}$ = final energy

${\text{U}}_{\text{i}}$ = initial energy