Heat can be useful, but it can also be annoying. Understanding heat and the flow of heat allows us to build heat sinks that prevent our computers from overheating, build better engines, and prevent freeway overpasses from cracking.

Temperature, kinetic theory, and the ideal gas law

In these videos and articles you'll learn about the Celsius and Kelvin temperature scales. The definition of a mole of a substance will be given. You'll also learn how the ideal gas law relates the pressure, volume, and temperature of a gas. Lastly, you'll learn how the Maxwell-Boltzmann distribution gives the probability of finding a gas molecule moving at a specific speed.
Thermodynamics part 1: Molecular theory of gases
Intuition of how gases generate pressure in a container and why pressure x volume is proportional to the combined kinetic energy of the molecules in the volume.
Thermodynamics part 2: Ideal gas law
To begin, Sal solves a constant temperature problem using PV=PV. Then he relates temperature to kinetic energy of a gas. In the second half of the video, he derives the ideal gas law.
Thermodynamics part 3: Kelvin scale and Ideal gas law example
Sal makes the case for the Kelvin scale of temperature and absolute zero by showing that temperature is proportional to kinetic energy. Then he explains that you need to use the Kelvin scale in the ideal gas law. To finish he does a sample ideal gas law problem.
Thermodynamics part 4: Moles and the ideal gas law
Sal explains the concept of a mole. Then he derives the molar version of the ideal gas law PV=nRT, where the gas constant R=831 J/molK.
Thermodynamics part 5: Molar ideal gas law problem
Sal uses the molar version of the ideal gas law to solve for the number of moles in a gas. He also shows how to convert this answer into number of molecules using Avogadro's number.
What is the ideal gas law?
Learn how pressure, volume, temperature, and the amount of a gas are related to each other.
Maxwell Boltzmann distribution
Using the Maxwell-Boltzmann distribution to visualize the distribution of speeds of particles at different temperatures.
What is the Maxwell-Boltzmann distribution?
In a gas, there are lots of molecules traveling at lots of different speeds. Here's a framework for thinking about that.

Laws of thermodynamics

In these videos and articles you'll learn how the first law of thermodynamics relates the change in internal energy of a gas, heat that enters the gas, and work done on the gas. PV diagrams will be discussed, as well as the four common thermal process; isobaric, isochoric/isovolumetric, isothermal, and isovolumetric processes. You'll also learn about how the second law of thermodynamics relates the entropy change to the multiplicity of microstates and the heat that enters a macroscopic system. The efficiency of a heat engine will also be explained.
Macrostates and microstates
The difference between macrostates and microstates. Thermodynamic equilibrium.
Quasistatic and reversible processes
Using theoretically quasi-static and/or reversible processes to stay pretty much at equilibrium.
First law of thermodynamics / internal energy
First law of thermodynamic and internal energy
More on internal energy
Getting more intuition of internal energy, heat, and work. Examples of using the first law to calculate work. 
What is the first law of thermodynamics?
Learn what the first law of thermodynamics is and how to use it.
Work from expansion
How a system can do work by expanding
PV-diagrams and expansion work
Why work from expansion is the area under the curve of a PV-diagram. Why heat is not a state function and internal energy is a state function. 
What are PV diagrams?
Learn what PV diagrams are and how to use them to find the change in internal energy, work done, and heat.
Proof: U = (3/2)PV or U = (3/2)nRT
Conceptual proof that the internal energy of an ideal gas system is 3/2 PV.
Work done by isothermic process
Isothermic and adiabatic processes. Calculating the work done by an isothermic process and seeing that it is the same as the heat added.
Carnot cycle and Carnot engine
Introduction to the Carnot cycle and Carnot heat engine
Proof: Volume ratios in a carnot cycle
Proof of the volume ratios in a Carnot cycle
Proof: S (or entropy) is a valid state variable
Proof that S (or entropy) is a valid state variable.
Thermodynamic entropy definition clarification
Clarifying that the thermodynamic definition of Entropy requires a reversible system.
Reconciling thermodynamic and state definitions of entropy
Long video explaining why entropy is a measure of the number of states a system can take on (mathy, but mind-blowing).
Entropy intuition
Introduces second law of thermodynamics. A discussion of entropy change in terms of heat and microstates .
Maxwell's demon
Maxwell's Demon: A thought experiment that seems to defy the 2nd Law of Thermodynamics
More on entropy
Distinguishing between microstates and macro states. How entropy S is defined for a system and not for a specific microstate.
Efficiency of a Carnot engine
Definition of efficiency for a heat engine. Efficiency of a Carnot Engine.
Carnot efficiency 2: Reversing the cycle
Seeing how we can scale and or reverse a Carnot Engine (to make a refrigerator)
Carnot efficiency 3: Proving that it is the most efficient
Proving that a Carnot Engine is the most efficient engine