Heat, Temperature, and Thermodynamics Flashcards
The sum of the potential and kinetic energies of the molecules in a substance is called the _____ ______ of the substance
internal energy
Heat definition
the kinetic energy of molecules transferred from a warmer substance to a cooler one
Temperature definition
the average kinetic energy of the molecules in a substance
Kelvin Temperature Equation
K = C + 273
Conversion between joules and calories
1 calorie = 4.186 joules
Linear Thermal Expansion
the increase in any one dimension of the solid. The change in length deltaL is proportional to the original length and the change in temperature of the solid
Volume thermal expansion
an increase in the volume of the solid. The change in volume deltaV is proportional to the original volume of the solid and its change in temperature
Three ways of transferring heat:
conduction, convection, and radiation
Conduction definition
The transfer of heat directly through a material, or by actual contact between two materials. Metals are typically good heat conductors. Insulators are not. By placing an iron skillet on a fire, heat is transferred by conduction to the handle of the skillet
Convection definition
The transfer of heat by the bulk movement of a fluid (liquid or gas). Water heated in a pan is an example of heat transfer by convection
Radiation definition
The process by which heat is transferred by electromagnetic waves. Microwave ovens and a roaring campfire are both examples of radiation
Heat absorbed or released by an object as a result of a change in temperature equation:
Q = mcdeltaT, (calories) where Q is the symbol for heat, m is the mass of the object, deltaT is the change in temperature and is equal to the final temperature minus the initial temperature, and c is the specific heat of the substance. Note that if the mass is in kg, the temperature in C, and the specific heat in kilocalorie/kg, the answer will be in kilocalories.
Specific heat c definition
a proportionality constant that gives an indication of the ease with which one can raise the temperature of something; the larger it is, the larger the amount of heat required to raise its temperature a certain number of degrees, and also the more heat is released if it cools by a certain number of degrees.
Heat capacity definition
the heat needed to raise the temperature of the object as a whole by 1 C or 1K
Heat equation for phase changes:
Q = mL, where m is the mass of the substance undergoing the phase change and L is the heat of transformation, the value of which depends on both the substance and the particular process we are talking about: vaporization, sublimation, or fusion (melting)
Three types of systems:
isolated, closed, and open
Isolated system definition
A system that cannot exchange energy or matter with the surroundings, like a well-insulated thermos flask
Closed system definition
A system that can exchange energy but not matter with the surroundings, like a test tube with a stopper in it
Open system definition
A system that can exchange both matter and energy with the surroundings, like a pot of boiling water allowing water vapor to escape into the air
First law of Thermodynamics
Law of conservation of energy. The change in the internal energy deltaU of a system is equal to the heat Q added to the system minus the work W that a system does: deltaU = Q - W (J). If work is done ON a system, W is negative and deltaU = Q + W
If work is done ON a system, its energy would ______
increase
If work is done BY the system, its energy would ______
decrease
Heat engine definition
any device that uses heat to perform work.
Three essential factors of a heat engine:
- Heat is supplied to the engine at a high temperature from a hot reservoir 2. Part of the input heat is used to perform work 3. The remainder of the input heat that did not do work is exhausted into a cold reservoir, which is at a lower temperature than the hot reservoir
Percent efficiency (%epsilon) equation
%epsilon = 100* Work/Qhot (the ratio of the work done to the amount of input heat)
The second law of thermodynamics
law of entropy. All spontaneous processes proceeding in an isolated system lead to an increase in entropy
