Chapter 3: Thermodynamics Flashcards
What is the study of thermodynamics?
Thermodynamics is the study of the flow of energy in the universe, as the flow relates to work, heat, entropy, and the different forms of energy. Classical thermodynamics concerns itself only with observations that can be made at the macroscopic level, such as measurements of temperature, pressure, volume, and work.
What is the zeroth law of thermodynamics?
What is the temperature at the molecular level? What is the temperature at the microscopic level?
Temperature at the molecular level is proportional to the average kinetic energy of the particles that make up the substance.
At the microscopic level, it is the difference in temperature between two objects that determines the direction of heat flow. When possible, heat moves spontaneously from materials that have higher temperatures to materials that have lower temperatures.
What is heat? What is the thermal equilibrium?
Heat itself refers to the energy transfer of thermal energy from a hotter object with higher temperature (energy) to a colder object with lower temperature (energy).
If the heat flows between two objects and thermal contact, then we can say that their temperatures are equal, and they are in thermal equilibrium.
What is the third law of thermodynamics?
The third law of thermodynamics states that the entropy of a perfectly organized crystal at absolute zero is zero Kelvin.
Graph showing absolute zero, freezing point of water, and boiling point of water for Fahrenheit, Celsius, and Kelvin.
What is body temperature in Fahrenheit, in Celsius?
98.6° F and 37°C
How do you convert between Fahrenheit and Celsius, and Kelvin and Celsius?
Example temperature conversion page 93
What is thermal expansion? What is the equation for the thermal expansion?
A change in the temperature of most solids results in a change in their length. Rising temperatures is causing increase in length, and falling temperatures cause a decrease in length. The amount of length change is proportional to the original length of the solid and the increase in temperature according to the equation.
Example of thermal expansion page 95
What is volumemetric expansion? Is it applicable to both liquids and solids? What is the equation for volumetric expansion?
Liquids experience thermal expansion, but the only meaningful parameter of expansion is volume expansion. The formula for volumemetric thermal expansion is applicable to both liquid liquids and solids.
What is the relationship between the coefficient of volumetric expansion and the coefficient of linear expansion?
Example volumetric expansion page 95
Concept check page 96 zeroth law of thermodynamics question 1
What is the zeroth law of thermodynamics?
The zeroth states that when two objects are both in thermal equilibrium with a third object, they are in thermal equilibrium with each other. By extension, no heat flows between two objects in thermal equilibrium.
Concept check page 96 zeroth law of thermodynamics question 2
While there may be a distance at which thermal equilibrium is impractical, there is no theoretical maximum distance. As long as two objects are in thermal contact, and at the same temperature, they are in thermal equilibrium.
Concept check page 96 zeroth law of thermodynamics question 3
Expansion is a result of an increase in dimension at all points along an object. If an object is initially longer, it will experience a greater expansion. This is also represented in the formula for thermal expansion because there is a direct relationship between length change and the initial length of an object.
Concept check page 96 zeroth law of thermodynamics question 4
False. Accuracy is related to an instrument, rather than the scale. In addition, Calvin uses the same scale as Celsius, so there are no practical differences in terms of accuracy.
What is the system and what are the surroundings?
The system is the portion of the universe that we are interested in serving or manipulating. The rest of the universe is considered the surroundings.
What is an isolated system?
An isolated system is not capable of exchanging energy or matter with their surroundings. As a result, the total change in internal energy must be zero. Isolated systems are very rare, although they can be approximated. A bomb colorimeter attempts to insulate a reaction from the surroundings to prevent energy transfer, and the entire universe can be considered an isolated system because there are no surroundings.
What is a closed system?
Closed systems are capable of exchanging energy, but not matter, with the surroundings. The classic experiments involving gases and vessels with movable pistons are examples of closed systems. For thermodynamic purposes, most of what will be encountered on test day will be a close system or will approximate a closed system
What are open systems?
Open systems can exchange both matter and energy with the environment. In an open system, not only does the matter carry energy, but more energy may be transferred in the form of heat or work. A boiling pot of water, human beings, and uncontained combustion reactions are all examples of open systems
What is a state function? Examples. What is a process function? Examples.
State functions are thermodynamic properties that are a function of only the current equilibrium state of a system. In other words, state functions are defined by the fact that they are independent of the path taken to get to a particular equilibrium state state functions include pressure (P), density, temperature (T), volume (V), enthalpy (H), internal energy (U), Gibbs free energy (G), and entropy (S)
Process functions, such as work and heat, describe the path taken to get to one state to another.
MCAT concept check 3.2 page 97 systems question 1
MCAT concept check 3.2 page 97 systems question 2
State functions are variables in independent from the path taken to achieve a particular equilibrium and our properties of a given system at equilibrium; they may be dependent on one another.
Process functions to find the path (or how the system got to it state) through variables, such as heat (Q) and work (W).
MCAT concept check 3.2 page 97 systems question 3
Pressure, density, volume, temperature, enthalpy, internal energy, Gibbs free energy, and entropy.
MCAT concept check 3.2 page 97 systems question 3
Pressure, density, volume, temperature, enthalpy, internal energy, Gibbs free energy, and entropy.
Draw simple phase diagram. Draw a heating curve. Describe which is which.
Express the first law of thermodynamics as an equation. Apply sign convention to the variables.
Use a car as an example to understand the first law of thermodynamics.
We all intuitively know that a car engine heats up, the tires heat up, the grease heats up, etc. And we all know that our car does work (displaces us with force).
The internal energy of the car is being “lost“ to the environment through heat, but also being used to do work (displace with force).
What is work? What are the units of work? What are three equations for work?
Work is the process by which energy is transferred as the result of force being applied through some distance. The unit of work is the joule (kg m^2/s^2).
What is a calorie (c)?
What is a kilocalorie (C)?
What are the units of heat?
The units of heat are joule, calorie, Calorie, and BTU.
What are the three kinds of heat transfer? Define.
Conduction is the direct transfer of energy from molecule to molecule through molecular collisions.
Convection is the transfer of heat by the physical motion of a fluid over a material.
Radiation is the transfer of energy by electromagnetic waves.
What is specific heat? What is the specific heat of water? What is the equation for heat transfer? What is the equation for heat transfer during a phase change?
The specific heat (c) of a substance is defined as the amount of heat energy required to raise 1 g of a substance by 1°C or one unit Kelvin.
There are six phase changes and a term for each of them. What are they?
Discuss heat of transformation regarding sweating.
Example, page 102 phase changes and heat.
Sketch a heating curve.
There were four special types of thermodynamic processes. What are they and how do they impact the equation for the first law of thermodynamics?
In each of these four cases, some physical properties held constant during the process.
Isothermal. No change in temperature. The manner by which internal energy changes is through changes in temperature. In an isothermal process, heat equals work.
Adiabatic. No heat exchange with the environment. Therefore, the change in internal energy equals the work done by or on the system.
Isobaric (constant pressure). There are multiple possible forms of the equation of the first law of thermodynamics.
Isovolumetric (isochoric). No change in volume, therefore no work accomplished. The change in internal energy equals heat flow into or out of the system.
Example page 104 work done by gas and change an internal energy of gas
Draw a representative graph of the temperature of a solid object as it is heated and goes through two phase changes to become a gas.
Draw a phase diagram while you’re at it.
This question is effectively asking us to create a heat curve and phase diagram.
Remember that a heat curve is T v Q and a phase diagram is P v T.
Consider hot tea cooling, a frozen drink melting, buildings crumbling, balloons deflating, and living things dying and decaying. Relate these to energy dispersion.
What is entropy? What is the equation for entropy? What are the units for entropy?
Entropy is the measure of the spontaneous dispersal of energy at a specific temperature.
How much energy is spread out, or how widely spread out energy becomes in a process.
Why is the second law of thermodynamics described as times arrow?
The second law has been described as times arrow because there is a unit directional limitation on the movement of energy by which we recognized before and after or new and old.
For example, you would instantly recognize whether a video of recording of an explosion was running backward or forward.
The second law ultimately claims that the entropy of the universe is increasing.
The universe is a closed, expanding system. Relate this to the second law of thermodynamics.
Example, page 107 calculation of change of entropy of a system
How does the book define natural processes, irreversible, and unnatural processes?
The book considers ice and liquid water and equilibrium at 0° temperatures when discussing a reversible reaction. Describe this.
The purpose of this slide is to get to the point of the difference between irreversible processes in physics while still being chemically reversible.
Equations and units to be familiar with in chapter 3 thermodynamics.
MCAT mastery chapter 3 thermodynamics page 88 question 1
For this question, we can either realize that a one degree change in Celsius is a 1.8° change in Fahrenheit.
Or we can convert 300 K to Celsius to Fahrenheit, and 310 Kelvin to Celsius to Fahrenheit and get a difference in 18°F.
1°C CHANGE IS EQUAL TO 1.8°F CHANGE.
