If you're seeing this message, it means we're having trouble loading external resources on our website.

If you're behind a web filter, please make sure that the domains *.kastatic.org and *.kasandbox.org are unblocked.

### Course: AP®︎/College Physics 2>Unit 2

Lesson 3: Laws of thermodynamics

# Second law of thermodynamics

Visit us (http://www.khanacademy.org/science/healthcare-and-medicine) for health and medicine content or (http://www.khanacademy.org/test-prep/mcat) for MCAT related content. These videos do not provide medical advice and are for informational purposes only. The videos are not intended to be a substitute for professional medical advice, diagnosis or treatment. Always seek the advice of a qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read or seen in any Khan Academy video. Created by David SantoPietro.

## Want to join the conversation?

• These videos are awesome, I paid for a MCAT prep online and I use this more. Love this, thanks you're a great teacher!
• some flat earthers realy need to see this.
• How can you ever find W in the Boltzmann equation? Isn't the number of possible states always infinite because there is an infinite number of places each molecule could be in and an infinite number of possible velocities for each molecule?
• Infinite? the area is enclosed with a specific number of particles. In comparison to a larger area with more particles, which one would have more microstates? We say infinite number of possibilities but wouldn't there really be just a large number of possible states?
• Does this explain "warming up" in a cool swimming pool?
(1 vote)
• No. "Warming up" in a cool swimming pool is a result of sensory adaptation. If your body freely exchanged heat with the much cooler, surrounding water, you would eventually experience hypothermia and likely die.
• around you talk about what you would feel if you were standing on the cold side of the room, but if I started on the hot side I would feel the cold moving in to the right side of the room, so it would feel like the cold is going into the hot, can you help me understand?
(1 vote)
• If you're standing on the hot side, the heat from your side would move over to cold side, making less heat for you, and therefore a cooler temperature. The result is the same, but the direction of heat flow is what's important.
• i still dont get how the entropy is related to how the heat moves.
(1 vote)
• Entropy is a measure of disorder, and increasing temperature increases the energy of the system and thus its disorder. heat is a form of energy transfer , temperature of a system can be increased by heat transfer ,hence increasing it's entropy.
• Does "cold" and "hotter" stand for less and more energy? Or lower and higher temperature? Because if the "hotter" object has a lower specific heat capacity it can have the same temperature as the "colder" object. Even though the hotter contains less energy (J), as in the example.
(1 vote)
• Interesting point, but I think the illustration of 6 blue and 6 red spheres infers identical atomic dynamics, albeit differing only by color.
Regardless, temp is one thing that will even out over time regardless of variance of heat capacity. Thus, hot tropical breezes will be cooled by cold ocean currents. (And vice versa).