what is the symbol of power?
what terms do we need to know?
Power is (watts) (W)
▸▸ kilowatt (kW) = 1000 Watt
▸▸ megawatt (MW) = 10^6 Watt
▸▸ gigawatt (GW) = 10^9 Watt.
1 Watt = 1 Joule per second (J s−1).
(Do not confuse with the kilowatt-hour (kWh),as its a unit of energy not power
-P = ΔW / Δt (Power = Work Done / Time Taken
-P=W/T
-time seconds
-work done joules
How to convert Celsius ( °C) to kelvin (k)?
How to convert kelvin(k) to Celsius ( °C) ?
-To convert Celsius (°C) to kelvin you have to add 273 or 273.15
-To convert kelvin(k) to Celsius (°C) you have to minus 273
what is the symbol of pressure?
what is the unit of pressure?
what does one pascal equal to?
What is the equation for pressure?
what is the equation for pressure in a fluid?
-The symbol of pressure is pa its unit is pascal (pa)
-1 Pascal = 1 Newton per square metre (N m−2)
-Equation–p=f/a
-f-force newtons
-a-area -m^2
*sheet
-Pressure = Density × Gravitational Field Strength × Height
what is energy?
what is work?
what is force?
-Energy – the ability to do work
-Work – is done whenever energy is transferred
-Force – a push or a pull
what is the work done equation?(basic)
-W=FXD
f=force(Newtons)
d=distance(Metres)
what is work done by a gas equation?
how do you work out the change in volume?
-DeltaW=pXDeltaV
-detlaW-work done by a gas
-P-pressure of the gas
-DetlaV-change in volume of the gas
Change in volume
-Final volume - intial volume
what is work done as a force?
-DeltsW=FXDelta s
-DeltaW=work done joules
-F-force newtons
-Deltas=displacement in the direction of the force
Efficiency Equations:
what is the basic efficiency equation?
what is the percentage efficiency (2)?
-E=useful energy output /total energy input
-Percentage efficiency=useful energy transferred/total energy supplied X 100
what is the efficiency for heat engines?
what is the efficiency for the maximum theatrical efficiency?
1−QOUT/QIN
𝑄in= heat energy absorbed from the hot source (J)
𝑄out= heat energy released to the cold surroundings (J
maximum theotrical effiency:
1-Tc/Th
Th= temperature of the hot reservoir (in kelvin, K)
𝑇C= temperature of the cold reservoir (in kelvin, K)
Law of conservation of energy:
what is the rule of conservation of energy?
what happens when one object does work on another and what law is this?
-Energy cannot be created or destroyed.It can only transfer from one object to another or change from eg kinetic to heat
-When one object does work on another (applies force and causes movement) the energy gained by the second object = energy lost by the first
-Because force always comes in equal and opposite pairs (newtons laws).Energy transfers are always balanced
-This means the total energy of the whole universe always stays the same even though energy may move around or change type
System and thermodynamics
What do scientists do because we can’t measure the system?
example?
what is thermodynamics?
-Because we can’t measure the whole universe scientists choose a system
-System=the part they are studying
-Surroundings=everything else outside the system
Example a cup of hot water=system.The room around it = surroundings
-Thermodynamics is largely about simplifying this so that they can studied and measured.
what are the 5 types of energy and their nature?
Mechanical energy-energy due to movement or position eg moving car
Electrical energy-energy from electric charges - static electricity
Chemical energy-energy stored in bonds inside substances eg food fuel batteries
Nuclear energy-energy stored in the nucleous of atoms released in nuclear reactions
Thermal energy - energy from the movement of particles in a material
what is the ideal gas equation?
what is about?
why is the ideal gas useful/
-Gases are made of constantly moving atoms/molecules and this explains how gas pressure volume and temperature are linked.
-Ideal gases:
- molecules are far apart no forces between them
-collisions are elastic no loss of energy
-molecules are tiny compared to the space the gas takes up
Equation
pV=NKT
p=pressure (Ps)
v=volume m^3
N=number of moles
T=temperature in kelvin
K=gas constant 1.38 idek
The ideal gas is useful because gases are at low pressures,high temperatures and far above their condensation point
Reversible processes (isothermal and adiabtic)
what is a reversible process?
why can no process be perfectyl reversible in real life?
-A theoretical process that can be reversed without any loss of energy or increase in entropy
-Because of friction,heat loss and imperfect insulation
Key points:
-Requires no friction
-No heat loss
-Perfect insulation and control
-Real processes are irreversible due to friction and heat loss
what is adiabatic process?
what are the four key points?
what is isothermal process?
wha are the 4 key points?
-An adiabatic process is one where no heat is transferred between the system and the surroundings.
Key points:
-Q = 0 (no heat transfer)
-Temperature changes
-Happens when there is perfect insulation or the process is very fast
-Used in ideal heat engine models
Isothermal process
-An isothermal process is one where the temperature remains constant.
Key points:
-Temperature stays the same
-Heat is transferred between the system and surroundings
-Internal energy stays constant (for an ideal gas)
-Slow process allowing heat exchange
First law of thermodynamics
what is internal energy and symbol?
what are 2 ways the internal energy of the gas might change?
-A gas in a container it has a certain amount of thermal energy known as internal energy (U)
-The particles in the gas are moving quickly,they have kinetic energy.The internal energy is the sum of these kinetic energies
-The two ways that internal energy of the gas might change:
1.It may gain or lose heat
-If the gas is given heat energy then its internal energy increases
-If the gas loses heat energy to its surroundings then its internal energy decreases
2.It may do work or have work done to it
-As the gas expands it does work.Internal energy decreases
-Work is done here to compress the gas.Internal energy increases
Equation:
Q=DELTAU+W
-Q = heat energy transferred to the system
-ΔU = change in internal energy of the system
-W = work done by the system (e.g. expansion against pressure)
-all joules
first law:
Energy cannot be created or destroyed, only transferred or converted from one form to another.
what does the second law of thermodyanmics tell us?
-Heat energy will always flow from a high temperature to a low temperature (unless work is done).
eg if i leave a hot cup of tea on my desk it will lose heat energy to its cooler surroundings
-It explains why no engine can be 100% efficient and why all real energy conversions lose some energy as waste heat.
Carnot cycle:
what is isothermal expansion?
what is adiabatic expansion?
what is isothermal compression?
what is adiabatic compression?
what is otto engine cycle steps?
-Isothermal expansion gas absorbs heat from the hot reservoir at constant temperature
-Adiabatic expansion - gas exapnds without heat transfer temperature drops
-Isothermal compression- Gas releases heat to cold reservoir at constant temp
-Adiabatic compression- gas compressed without heat transfer temperature rises
Otto engine cycle:
Intake
-Piston moves down, air-fuel enters
-Compression
Piston moves up, mixture compressed (adiabatic approx.)
-Power
Spark ignites fuel at near-constant volume (combustion)
-Exhaust Piston pushes gases out
what is the heat engines?
examples/
-Heat engines take in thermal energy from a hot reservoir, convert some of it into useful mechanical work, and release the remaining heat to a cold reservoir. Their efficiency depends on the temperature difference: a bigger difference gives higher efficiency. They cannot convert all heat to work because of the second law.
Examples:
-Petrol engine is a heat engine
-Steam does work pushing a piston in a steam engine
-A steam turbine in a power station
what are refigerators?
what are heat pumps?
-Refrigerators use work input (electrical energy) to remove heat from a cold space and transfer it to a warmer surrounding. They operate against the natural heat flow direction, meaning work is required. Their performance is measured by the coefficient of performance (COP), which compares heat removed to work input.
-Heat pumps use work to take heat from outside (cold) and move it inside a building (warm). They are more energy-efficient than heaters because they move heat rather than create it. The higher the temperature difference, the harder the pump works and the lower the COP.
what are the changes of state?
what is the gas to liquid?
what is solid to liquid?
what is liquid to gas?
-Liquid,solid and gas
-Gas to liquid is condensation
-Solid to liquid is melting
-Liquid to gas is evaporation
Graph
1.Gas is cooling down,loosing heat energy
2.Gas is condensing into a liquid,temperature stays the same,even though its loosing energy because molecules are forming bonds.
3.Liquid cooling down,liquid loses heat energy to its surroundings
4.The liquid freezes into a solid,more bonds are formed.Temp stays the same
5.Solid cools down,loses heat it will eventually be thermal equilbirium there will be no net gain or loss of heat
-Change of state temperature does not change.
what is latent heat and how do we calculate it?
what is specific latent heat?
what is the equation?
what is specific latent heat of fusion?
what is specific latent heat of vaporasation?
and condensation?
-energy required to change the state of 1 kg of a substance without changing its temperature
-equation DELTAQ=DELTAml
Specific heat of fusion
-The energy needed to change 1 kg of a solid into a liquid at its melting point, without any change in temperature.
Specific Latent Heat of Vaporisation
-Definition: The energy needed to change 1 kg of a liquid into a gas at its boiling point, without any change in temperature.
Specific Latent Heat of Condensation
-Definition: The energy released when 1 kg of gas changes into a liquid at its boiling point, without any change in temperature.
what is the specific heat capacity?
Specific heat capacity is the heat energy reabsorbed or released by a substance when it gets warmer or cooler without changing state.
ΔQ=mcΔT
-ΔQ = thermal energy transferred (J)
-m = mass (kg)
-c = specific heat capacity (J kg⁻¹ °C⁻¹ or J kg⁻¹ K⁻¹)
-ΔT = change in temperature (°C or K)
IMPORTANT
-If the object gains heat, ΔQ is positive
-If the object loses heat, ΔQ is negative
What does isentropic
mean?
what is charles law?
what is boyles law?
what is gay lussac’s?
-A process involving no change in entropy
-Charles law is at constant pressure, the volume of the gas and absolute temperature are directly proportionalv/t=constant
-Boyle’s law At constant absolute temperature, the pressure of the gas and the volume of the gas are inversely proportional.p x v = constant.
Gay lussacs
-the pressure of a gas is directly proportional to the Kelvin temperature if the volume is constant
