10TH GRADE · THERMODYNAMICS
Thermal processes and efficiency
Heating, phase transitions, adiabatic process and heat engine.
The entire theory of the lesson is collected here; you can read it without an account. In interactive mode, the same theory appears as cards, followed by questions. with checking the answer and task, and progress is saved.
Basic Concepts
Heat transfer
Transfer of internal energy between bodies without performing mechanical work on macroscopic movement.
Energy is spontaneously transferred from a hotter body to a colder body by conduction, convection or radiation.
Phase transition
Transition of matter between states of aggregation.
During melting or boiling, the supplied energy changes the relative positions of the particles, so the temperature usually remains constant.
Adiabatic process
A process without heat exchange between the system and the environment.
Here Q = 0: temperature and internal energy change only due to work on the gas or work on the gas.
Heat engine
A device that cyclically converts part of the received heat into mechanical work.
The machine receives heat from the heater, converts some of it into work, and gives the rest to the refrigerator - therefore, the efficiency is always less than 100%.
Physical quantities
Specific heat capacity
Heat to change the temperature of a unit mass by one degree.
Unit: joule per kilogram kelvin ·
Temperature change
Difference between final and initial temperatures.
Unit: degrees Celsius ·
Specific heat of combustion
The heat released during complete combustion of a unit mass of fuel.
Unit: joule per kilogram ·
Specific heat of fusion
Heat to melt a unit mass at the melting point.
Unit: joule per kilogram ·
Specific heat of vaporization
The heat required to convert a unit mass of liquid into vapor at its boiling point.
Unit: joule per kilogram ·
Heat engine efficiency
The fraction of the heater's heat converted into useful work.
Unit: dimensionless quantity
Heater heat
Energy received by the working fluid from the heater.
Unit: joule ·
Refrigerator warmth
Energy transferred by the working fluid to the refrigerator.
Unit: joule ·
Heater temperature
Absolute temperature of the hot reservoir.
Unit: kelvin ·
Refrigerator temperature
Absolute temperature of the cold reservoir.
Unit: kelvin ·
Lesson formulas
Warmth when heating
The amount of heat is equal to the product of mass, specific heat capacity and temperature change.
Heat of combustion
When fuel burns completely, heat is released that is proportional to its mass.
Heat of Melting
The heat of fusion at a constant temperature is proportional to the mass of the substance.
Heat of vaporization
The heat of vaporization at a constant temperature is proportional to the mass of the liquid.
First law for the adiabatic process
Without heat exchange, internal energy changes only due to the work of external forces.
Condition: There is no heat exchange with the environment.
Heat engine efficiency
Efficiency is equal to the ratio of useful work to the heat of the heater.
Efficiency of an ideal Carnot machine
The maximum efficiency of a reversible machine is determined by the temperatures of the heater and refrigerator.
Related formulas
The same formulas in the reference, with symbols and units.
Tasks on the topic
Statements, answer options and the walkthrough.