FSc ICS Notes Physics XI SQ & Definitions Chapter 11 Heat and Thermodynamics

FSc ICS Notes Physics XI Short Questions & Definitions Chapter 11 Heat and Thermodynamics 1st Year Physics Notes Online Taleem Ilm Hub

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Heat: i) Heat is a form of energy associated with molecular motion. ii) Heat is energy that flows between a system and its environment by virtue of a temperature difference  between them.

Temperature: Degree of hotness as determined by a thermometer.

Absolute zero: The temperature of –273.16 oC at which the volume of a gas theoretically becomes zero. It is taken as zero on the Kelvin scale of temperature.

Thermodynamics: Study of quantitative relationships between heat and other forms of energy.

Technology: The science of industrial arts and manufactures.

Hypothesis: A theory, which may or may not prove to be true.

Postulate: A statement which is taken for granted as a fact; to assume without proof.

Law: A scientific statement of the action and relation of things in nature, observed to be always the same under given conditions with the same result performed anywhere in the world.

Kinetic theory: A theory explaining physical properties in terms of the motion of particles.

Kinetic theory of gases: The molecules or atoms of a gas are in continuous random motion and the pressure exerted on the walls of a containing vessel arises from the bombardment by these fast moving particles.

Brownian motion: The continuous random motion of microscopic solid particles (of about 1 micrometer in diameter) when suspended in a fluid medium.

Microscopic: Very small; invisible without a microscope.

Macroscopic state: The state of matter characterized by the statistical properties of its components. Kinetic theory is an analysis of the macroscopic state.

Microscopic state: The state of matter characterized by the actual properties of each individual elemental component. Quantum theory is typically an analysis of the microscopic state.

Pressure: At a point in a fluid, the force exerted per unit area on an infinitesimal plane situated at the point.

Density: The ratio of the mass of a substance to its volume.

Pascal’s law: Pressure applied at any point of a fluid at rest is transmitted without loss to all other parts of the fluid.

Temperature: Degree of hotness as determined by a thermometer.

Boyle’s law: The volume of a given mass of a gas is inversely proportional to the pressure, if the temperature is kept constant.

Charles’ law: The volume of a given mass of a gas is proportional to its absolute temperature provided the pressure of the gas is kept constant.

General gas law: The product of pressure and volume of a given mass of a gas is proportional to its absolute temperature.

Ideal gas: A gas, which obeys the gas laws at all temperatures and pressures.

Real gas: A gas, which does not obey the gas laws at all temperatures and pressures.

Mole: i) The amount of that substance whose mass, expressed in grams, is numerically equal to the molecular weight of the substance. ii) A quantity which contains Avogadro’s number of units i.e. atoms, molecules, ions or whatever under consideration.

Avogadro’s law: Equal volumes of all ideal gases at same temperature and pressure contain equal number of molecules.

Avogadro’s number (or Avogadro constant): The number of atoms or molecules in one mole of a substance. It has the value 6.02252 x 10(23).

Rotation: Turning around its own axis or centre.

Internal energy: Total heat energy retained by the system in the form of potential energy and kinetic energy.

Enthalpy (H): i) The total heat content of a system is termed as enthalpy of a system. ii) The sum of the internal energy and the product of pressure and volume of a system; H = U + PV

Function of state: It is a macroscopic property of a system which has some definite value for each state and which is independent of path in which the state is reached; e.g. P,V,T & U.

Work: The product of magnitude of force and that of displacement in the direction of force.

Mechanical: Pertaining to the laws of matter and motion; produced by machines.

Mechanical equivalent of heat (J): Amount of work obtainable by the complete conversion of unit quantity of heat into mechanical work.

Mechanical work: Work done with some mechanical device, e.g. work done in heat engine.

Mechanical energy: The energy transmitted by a machine; energy in the form of mechanical power; the kinetic plus potential energy, if there is no frictional loss.

Environment: Conditions around something, which influence the working of that thing.

Zeroth law of thermodynamics: If systems A and B are each in thermal equilibrium with a third system C, then A and B are in thermal equilibrium with each other.

First law of thermodynamics:

i) In any thermodynamic process, when heat Q is added to a system, this energy appears as an increase in the internal energy ΔU stored in system plus work W done by the system on its surroundings.

ii) When heat is converted to another form of energy, or when other forms of energy are converted into heat, there is no loss of energy.

Thermocouple:

i) Two dissimilar metallic conductors joined at their ends.

ii) Junction of two dissimilar metals, in which an emf is generated by reason of a temperature difference.

Piston: A small solid cylinder of metal or wood, fitting exactly, and moving up and down in

a cylinder or tube.

Cylinder: A hollow vessel or chamber like empty space in a solid in which force is executed

on the piston of a steam engine.

Monitor: A device that observes and records selected activities within a system for analysis.

Millivoltmeter: A meter used to measure electrical voltage whose range is measured in 10(-3) volts.

Metabolism: i) Energy transforming processes that occur within an organism. ii) The sum of the chemical reactions occur within living organisms.

Cell: A tiny, usually microscopic , mass of protoplasm, one of the units of structure of living

matter in both plants and animals.

Protoplasm: The vital substance from which develops all forms of animal and plant life.

Organism: Anything that has life in itself; a body composed of parts performing special

duties, but mutually dependent.

System: A collection of matter which has a distinct boundary.

Surroundings: The remaining portions around a system are called surroundings.

Closed system: A system for which there is no transfer of mass across the boundary.

Isolated system: A system for which there is no transfer of mass and energy across the

boundary.

Isothermal process: The process in which the temperature of the system remains constant.

Isotherm: The curve representing an isothermal process in P-V diagram is called isotherm.

Adiabatic process: The process in which no heat flows into or out of the system.

Adiabat: The curve representing an adiabatic process in P-V diagram is called adiabat.

Isobaric process: The process in which the pressure of the system remains constant.

Isochoric process: The process in which the volume of the system remains constant.

Specific heat: The amount of heat energy required to raise the temperature of unit mass

through one degree.

Molar specific heat: The amount of heat energy required to raise the temperature of one mole of a substance through 1 K.

Molar specific heat at constant volume (Cv): The amount of heat energy required to raise the temperature of one mole of a gas through 1 K at constant volume.

Molar specific heat at constant pressure (Cp): The amount of heat energy required to raise the temperature of one mole of a gas through 1 K at constant pressure.

Universal gas constant: The constant of proportionality R in the equation of state, pV = nRT, of an ideal gas. R has the value 8.2057 x 10(-21) atm/mole K.

Reversible process: If the process can be reversed in such a way that the system and its surroundings are both brought back to their original states, then the process is said to be reversible.

Irreversible process: If a process can not be retraced in the backward direction by reversing the controlling factors, it is an irreversible process.

Liquification: Changing into liquid.

Evaporation: A change of state from solid or liquid to gas (or vapour).

Sublimation: It is a process in which a solid, when heated, vapourizes directly without passing through the liquid place.

Engine: A mechanical device that changes a physical force in one form such as heat, into another form more easily used.

Heat engine: A device which transforms heat energy into mechanical energy.

Steam engine: A heat engine in which water is boiled in a vessel covered with a piston, the steam inside tries to push the piston up showing the ability to do work.

Reservoir: A place where anything, as water, is collected and stored up for use; e.g. large trees in a jungle.

Heat reservoir : It is supposed to be so big that its temperature remains constant even if some heat enters or leaves the reservoir.

Hot reservoir (or Source):A hot body, which can supply heat at a high temp. to a cold body.

Cold reservoir (or Sink):A cold body, which can receive heat at a low temperature from a hot body.

Second law of thermodynamics: i) According to Lord Kelvin’s statement, “It is impossible to devise a process which may convert heat, extracted from a single reservoir, entirely into work without leaving any change in the working system”.

ii) According to Clausius statement, “It is not possible in a cyclical process for heat to flow from one body to another body at higher temperature, with no other change taking place”.

Carnot engine: An ideal heat engine, free from all the imperfections of actual engines, and hence never realized in practice.

Carnot cycle: A cycle in which reversible process occurs.

Third law of thermodynamics: It is impossible by any procedure, no matter how idealized, to reduce any system to the absolute zero of temperature in a finite number of operations.

Efficiency: The ratio of the useful work output of a machine to total work input.

Thermal equilibrium:

i) The condition of a system in which the net rate of exchange of heat between the components is zero.

ii) If two bodies at different temperatures are placed together, heat transfer occurs until they have the same temperature. They are then at thermal equilibrium.

Mechanical equilibrium: A state of a system in which the properties (e.g. p,V,T, etc) do not change with time.

Carnot Theorem: No heat engine can be more efficient than a Carnot engine operating between the same two temperatures.

Extension of Carnot theorem: All Carnot’s engines operating between the same two temp. have the same efficiency, irrespective of the nature of the working substance.

Isothermal expansion: The expansion in which the temp. of the system remains constant.

Triple point: The only point at which the gas, solid, and liquid phases of a substance can coexist in equilibrium. The temperature of the triple point of water is defined to be 273.16 Kelvin.

Petrol engine: An engine based on the principle of Carnot cycle. It undergoes 4 processes; 

1. intake of petrol air mixture into the cylinder with a outward piston.
2. adiabatic compression of the mixture with the inward piston
3. a spark fires the mixture causing its adiabatic expansion that forces the piston to move outward which delivers power to crank shaft to derive the flywheel.
4. the residual gases are expelled from the outlet valves and piston moves inward.

Carburetor:

i) A device used to charge air with gas from petrol for producing light or power.

ii) A device in an engine that mixes liquid fuel and air in the correct proportions, vaporizes them, and transfers the mixture to the cylinders.

Valve: A mechanical device for opening and closing the movement of a gas or liquid; a fold which allows the movement in one direction only.

Spark plug: An ignition device, the insulated conductor set in the wall or top of each cylinder. At the inner end of the spark plug is a small gap between two wires. The high voltage current arcs across this gap, yielding the spark that ignites the fuel mixture in the cylinder.

Flywheel: A large heavy wheel, with large moment of inertia, used in mechanical devices.

Piston: A solid cylinder of metal or wood, fitting exactly and moving up and down in a tube.

Crank: Of a boat, easily upset; opposite of stiff.

Shaft: Anything shaped like an arrow, as the stalk of a plant or broken handle of cricket bat.

Crankshaft: A shaft driven by a crank.

Petroleum: Naturally occurring green to black coloured mixtures of crude hydrocarbon oils, found as earth seepages or obtained by boring.

Gas oil: A petroleum distillation fraction intermediate between kerosene and light lubricating oil. Slightly more viscous grades are used as diesel fuels.

Diesel (or diesel fuel): Fuel used for diesel (compression ignition) engines. The composition varies but is near that of gas oil.

Petrol (or gasoline): A light hydrocarbon liquid fuel for spark-ignition engines; a complex mixture consisting mainly of hydrocarbons such as hexane, heptane and octane.

Diesel engine: Its like a petrol engine but without sparkplug. It undergoes four processes;

1. the diesel is sprayed into the cylinder with a outward piston.
2. adiabatic compression of the mixture with the inward piston.
3. fuel mixture ignites on contact with air due to high temperature causing its adiabatic expansion that forces the piston to move outward which delivers power to crank shaft to derive the flywheel.
4. the residual gases are expelled from the outlet valves and piston moves inward.

Entropy: The physical quantity, which describes the ability of a system to do work; describes disorder of a system. Mathematically, ΔS = ΔQ / T

Electric motor: The machine which converts electrical energy into mechanical energy.

Battery: A number of similar units, such as electric cells, working together.

Power plant (or generating station): A complete assemblage of plant, equipment, and the necessary  buildings at a place where electric power is generated on a large scale.

Nuclear power plant: A power plant using a nuclear reactor as the source of energy.

Nuclear reactor: A device in which nuclear reactions take place on a large scale.

Solid state laser: A laser consisting chiefly of semi-conducting materials or compounds.

Internal combustion engine: An engine in which the fuel is burned within the engine cylinders.

External combustion engine: An engine in which the fuel is burned outside the engine cylinders, in a separate boiler.

Fluorescent lamp: A lamp in which light is generated by an electrical discharge through a low pressure gas, causing it to emit radiation.

Incandescent lamp: An electric lamp in which light is produced by the heating effect of a filament.

Incandescence: The radiation of visible light by a surface at high temperature.

Fluorescence: The absorption of energy by atoms, molecules, etc. followed by immediate emission of electromagnetic radiation as the particles make transitions to lower energy states.

Environmental crisis: Global scale problems created by man in the physical environment and by use of physical resources. It concerns with temperature, humidity, atmosphere and contamination.

Thermal pollution: The discharge of heated gases into the surrounding air, causing a rise in air temperature that sometimes affects local weather conditions.

Metabolism: i) Energy transforming processes that occur within an organism. ii) The sum of the chemical reactions occur within living organisms.

Futile: Useless; of no importance; worthless.

Ecology: The study of the relation of plants and animals to their environment and each other.

Ecological balance: The balance between the relation of plants and animals to their environment and each other.

Fragile: Easily broken; delicate.

Engineering: The application of scientific and mathematical principles to practical ends; such as the design, manufacture, and operation of structures, machines, processes and systems.

Engineer: One who is trained or professionally engaged in a branch of engineering.

Mechanical engineer: The engineer who deals the generation and application of heat and mechanical power and the design, production, and use of machines and tools.

Boiler: A strong metallic vessel in which steam is produced for diving engines.

Written By: Asad Hussain