Keep the Heat B/Thermodynamics C

[-274degreesC]

What is the point of Gibbs free energy? There is a formula and everything but I am unclear as to what it is even used for. Also, can someone explain the concept of enthalpy? Again, I have the formula but not a working understanding of what it is.

[Skink]

I would most certainly hope free energy doesn't show up on a B division test. Talk about age appropriate! Anyways, Gibbs free energy is called what it is because it was discovered by some guy called Gibbs, I think. Look up the technical definition, but, practically, it's a thermodynamic parameter used to determine is a process is spontaneous. Spontaneity is whether or not a process happens naturally, by itself, without adding energy to drive the reaction. Nonspontaneous processes (positive value of delta G) do not happen naturally and require energy. We want to be able to predict if the chemical reactions we're interested in occur spontaneously. We can predict that ahead of time by calculating the free energy of the reaction. The only equation of interest would probably be G=H-TS and variations (i.e. delta signs in front of each parameter).

Enthalpy, H, is another thermodynamic parameter. In plain English? I'll let someone else take this.

[-274degreesC]

I didn't really think I would need to know it either but there is a test from the Coolidge Invitational in the SciOly Test Exchange that talks about it so I just thought it would be useful to have a conceptual understanding of what it is. Thanks for explaining.

[cyanophycean314]

Going off what skink said, the equation is generally ΔG = ΔH - TΔS.

ΔG is the change in Gibbs Free Energy.
ΔH is the change in enthalpy, which is usually the heat released/absorbed by a process (basically Q). In reality, H is another state variable (like U and T) that has a formal definition, you can go look it up. + if heat goes in (endothermic). - if heat goes out (exothermic)
T is the temperature the process occurs at. In Kelvin.
ΔS is the change in entropy or disorder for the process. + if more disorder, - if less disorder.

Yeah, most competitions usually don't deal with this stuff. This is usually considered part of thermochem, and not tested.

[ScienceOlympian]

Any good tips, notes, or websites for the test? And what are the best materials for the box?

[sjwon3789]

Any good tips, notes, or websites for the test? And what are the best materials for the box?

There's notes on http://scioly.org/wiki/index.php/Keep_the_Heat to start out with and study the tests which you probably know..
The common materials are probably cotton and aluminum foil. I think the materials used besides aluminium foil doesn't really matter as long as it works in the method your using. So, a better question would be, what are some methods used for the box?

Read, Read, Read your rules daily...

[JustDroobles]

Any good tips, notes, or websites for the test? And what are the best materials for the box?

If you have the time, I would suggest Khan Academy. https://www.khanacademy.org/science/phy ... modynamics

[foreverphysics]

Any good tips, notes, or websites for the test? And what are the best materials for the box?

Quite honestly, the wiki probably contains everything that you need to know--that is, if your state likes following the rules.

[Skink]

It's loaded with information, but I certainly wouldn't go so far as to say it's everything. For example, it lacks information regarding common physical observations. It's pretty theory-heavy. Additionally, I wouldn't look at just definitions for some of the stuff in there (especially the thermo processes) without figures which requires additional research.

That said, it's definitely a good place to frame your studying with. Regarding what to use in the box, do some research. I'd start with R values and go from there. You can read back for discussion in this and last season's topics about this, but you'd have to sift through a lot of other discussion.

[cyanophycean314]

Any good tips, notes, or websites for the test? And what are the best materials for the box?

If you grab any decent physics book, there will be 3-4 chapters there describing thermo. It will cover all that you need. College Physics, University Physics, they will all work. This will take a while, but that's how I learned it. The wiki is pretty nice as people have said.

As for materials, I don't know what the best would be, but we have used cardboard, cotton, aluminum foil, and shredded jeans.