Thermodynamics Flashcards
Temperature definition
Thought of as the degree of hotness of an object. It indicates the direction of internal energy flow. It diffuses from high to low.
How are temperate scales formed?
Two standard degrees of hotness are chosen and called the fixed points. Numbers are assigned to them.
Celsius scale
Divided into 100 increments known as degrees °C.
Fahrenheit scale
Freezing point of water is 32° F and boiling point is 212° F.
Divided into 180 increments known as degrees ° F.
A Fahrenheit degree is 5/9ths as large as a Celsius degree.
Fahrenheit to Celsius
°C = (°F -32) / 1.8
Celsius to Fahrenheit
°F = (1.8 x °C) + 32
What is absolute zero?
0 K = -273°C
Celsius to Kelvin
Tk = Tc +273
The freezing point of water is 273K, and boiling point is 373K
Fahrenheit to Rankine scale
Tr = Tf + 460°
The freezing point of water on the Rankine scale is 492°R, boiling point is 672°R.
What is Heat (Q)?
Heat (Q) is a form of energy that when added to a body, increases the internal energy content of the body, causing a rise in temperature.
What is the S.I. unit for heat?
Joule (also Kcal)
What is heat capacity (c) ?
Defined as the ratio of heat supplied to an object or specimen to its consequent rise in temperature. The unit is JK^-1.
What is specific heat capacity (c)?
Defined as the heat energy required to increase the temperature of 1kg of a substance by 1 K. Unit is J kg^-1 K^-1.
Specific heat capacity equation
Q = mc🔺ø
1st Law of Thermodynamics
The heat energy supplied to a system either increases the internal energy of the system or enables it to do work
Q = 🔺U + W
Where
Q = net heat input
🔺u = change in internal energy
W = net work output
2nd Law of Thermodynamics
Heat cannot be transferred from one body to a second body at higher temperature.
The entropy of a closed system increases with time.
🔺U = T🔺s - W
Where 🔺U = change in internal energy T = temperature 🔺s = change in entropy W = work done
What is entropy ?
A measure of the unavailability of its energy to do work
What is heat of combustion ?
The heat of combustion is the energy released as heat when a compound undergoes complete combustion with oxygen under standard conditions .
What are heat engines?
Convert heat into work
What is Molar heat capacity at constant volume (Cv)
The heat required to produce a unit rise of temperature in one mole of gas when the volume is kept constant.
Molar heat capacity at constant pressure (Cv)
The heat required to produce a unit rise of temperature in one mole of gas when its pressure remains constant.
What are the three types of expansion process in gases?
Isobaric, Isothermal and Adiabatic.
What is an isobaric gas expansion process?
takes place at a constant pressure.
What is an isothermal gas expansion process ?
Takes places at a constant temperature.
