THERMODYNAMICS
There’s a relationship between mechanical work (energy given when force
pushes/applies to an object) and thermal effect.Thermodynamics is the
branch of physics that deals with the study of heat, work and internal energy
and their interconversion.To describe thermal phenomena quantitatively, we
must define: Temperature , Thermal energy , Internal energy
Heat energy – energy in form of heat, it is useful for cooking food,lighting
houses, running trains and planes.
Burning something produces heat energy, but even mechanical work
produces heat energy without a flame. Examples: 1. Compression of gas in
the pump -- When a bicycle tyre is inflated using a pump, the pump becomes
hot. 2. Friction between hands - When hands are rubbed together, a feeling of
warmth is produced.
A glass of ice-cold water warms up when left in a hot environment and hot
water cools gets warm in room temp. these are examples of energy
exchange between system and surroundings. Energy transfer continues until
thermal equilibrium is reached. Thermal equilibrium - when System and
surroundings have the same temperature. (hot water and room temp is
same). Direction of energy transfer: Always from higher temperature to lower
temperature. From hot water
9 to normal room.
Heat is the form of energy transferred between a system and its surroundings
because of temperature difference. (there can be 1 system or even more).
Joule found the nature of heat which is : Heat is due to the mechanical
motion of molecules. Units of heat: Calorie (cal): One calorie is the amount of
heat required to raise the temperature of 1 g of water each 1°C increase.
At thermal equilibrium: The value of temperature is the same for all bodies.
Temperature of a body is the property which determines whether or not it is
in thermal equilibrium with other bodies.
I) A thermodynamic system is a definite quantity of matter seperately chosen
for study. Every system is enclosed by an arbitrary surface, which is called its
boundary. The boundary: 1. May enclose (close off sides of/be walls of ) a
solid, liquid or gas, 2. May be real or imaginary 3. May be at rest or in motion
4. May change its size and shape
The region of space other than the system is called its surroundings. Types of
Thermodynamic Systems: (a) Open system : It is a system which can exchange mass and
energy with the surroundings. A water heater is an open system.
Closed system : It is a system which can exchange energy but not mass with the
surroundings. A gas enclosed in a cylinder fitted with a piston is a closed system.
, Isolated system : It is a system which can exchange neither mass nor energy with the
surrounding. Ex: A filled thermos flank.
(ii) Thermodynamic Variables (or Coordinates) – in prev chap we learnt - To
describe motion, we use mass, position and velocity. To describe a
thermodynamic system, we use physical properties like: temperature (T),
pressure (P), and volume (V). These are called thermodynamic variables.
(iii) Indicator Diagram – js like velocity-time graph, A thermodynamic system is
studied using a pressure–volume (P–V) graph. An indicator diagram is a
Pressure-volume graph. It shows how pressure changes with volume
during a thermodynamic process.
Work Done from Indicator Diagram – work done by the system…
Indicator diagrams are useful when:
The relationship between P and V is not known. Used for calculating work.
Work done on the system is taken as negative (increases energy), work done by system is
positive (reduces its energy). Work is a path-dependent quantity. It depends
on path and initial final states.
THERMODYNAMIC EQUILIBRIUM
1. Thermal equilibrium yk 2. 👉 Mechanical equilibrium: A system is in
mechanical equilibrium when all forces are balanced and no part of the
system moves or changes due to pressure or stress. Example: The Earth’s
middle (equator) pushed outward as it cooled and settled into a stable shape. 3.
Chemical equilibrium: When a system has components that react chemically
and the reactions stop after some time.
Thermodynamic equilibrium: is A system having thermal, mechanical, and
chemical equilibria. Macroscopic properties do not change with time.
A thermodynamic process occurs when thermodynamic properties/variables change while
going from one equilibrium state to another.
Example: Expansion of gas in a cylinder at constant pressure due to heating. Path: is
curved / A graphical representation of a thermodynamic process.
Types of Thermodynamic Processes
There’s a relationship between mechanical work (energy given when force
pushes/applies to an object) and thermal effect.Thermodynamics is the
branch of physics that deals with the study of heat, work and internal energy
and their interconversion.To describe thermal phenomena quantitatively, we
must define: Temperature , Thermal energy , Internal energy
Heat energy – energy in form of heat, it is useful for cooking food,lighting
houses, running trains and planes.
Burning something produces heat energy, but even mechanical work
produces heat energy without a flame. Examples: 1. Compression of gas in
the pump -- When a bicycle tyre is inflated using a pump, the pump becomes
hot. 2. Friction between hands - When hands are rubbed together, a feeling of
warmth is produced.
A glass of ice-cold water warms up when left in a hot environment and hot
water cools gets warm in room temp. these are examples of energy
exchange between system and surroundings. Energy transfer continues until
thermal equilibrium is reached. Thermal equilibrium - when System and
surroundings have the same temperature. (hot water and room temp is
same). Direction of energy transfer: Always from higher temperature to lower
temperature. From hot water
9 to normal room.
Heat is the form of energy transferred between a system and its surroundings
because of temperature difference. (there can be 1 system or even more).
Joule found the nature of heat which is : Heat is due to the mechanical
motion of molecules. Units of heat: Calorie (cal): One calorie is the amount of
heat required to raise the temperature of 1 g of water each 1°C increase.
At thermal equilibrium: The value of temperature is the same for all bodies.
Temperature of a body is the property which determines whether or not it is
in thermal equilibrium with other bodies.
I) A thermodynamic system is a definite quantity of matter seperately chosen
for study. Every system is enclosed by an arbitrary surface, which is called its
boundary. The boundary: 1. May enclose (close off sides of/be walls of ) a
solid, liquid or gas, 2. May be real or imaginary 3. May be at rest or in motion
4. May change its size and shape
The region of space other than the system is called its surroundings. Types of
Thermodynamic Systems: (a) Open system : It is a system which can exchange mass and
energy with the surroundings. A water heater is an open system.
Closed system : It is a system which can exchange energy but not mass with the
surroundings. A gas enclosed in a cylinder fitted with a piston is a closed system.
, Isolated system : It is a system which can exchange neither mass nor energy with the
surrounding. Ex: A filled thermos flank.
(ii) Thermodynamic Variables (or Coordinates) – in prev chap we learnt - To
describe motion, we use mass, position and velocity. To describe a
thermodynamic system, we use physical properties like: temperature (T),
pressure (P), and volume (V). These are called thermodynamic variables.
(iii) Indicator Diagram – js like velocity-time graph, A thermodynamic system is
studied using a pressure–volume (P–V) graph. An indicator diagram is a
Pressure-volume graph. It shows how pressure changes with volume
during a thermodynamic process.
Work Done from Indicator Diagram – work done by the system…
Indicator diagrams are useful when:
The relationship between P and V is not known. Used for calculating work.
Work done on the system is taken as negative (increases energy), work done by system is
positive (reduces its energy). Work is a path-dependent quantity. It depends
on path and initial final states.
THERMODYNAMIC EQUILIBRIUM
1. Thermal equilibrium yk 2. 👉 Mechanical equilibrium: A system is in
mechanical equilibrium when all forces are balanced and no part of the
system moves or changes due to pressure or stress. Example: The Earth’s
middle (equator) pushed outward as it cooled and settled into a stable shape. 3.
Chemical equilibrium: When a system has components that react chemically
and the reactions stop after some time.
Thermodynamic equilibrium: is A system having thermal, mechanical, and
chemical equilibria. Macroscopic properties do not change with time.
A thermodynamic process occurs when thermodynamic properties/variables change while
going from one equilibrium state to another.
Example: Expansion of gas in a cylinder at constant pressure due to heating. Path: is
curved / A graphical representation of a thermodynamic process.
Types of Thermodynamic Processes
