Online reading assignment: internal energy conservation

Physics 205A, fall semester 2017
Cuesta College, San Luis Obispo, CA

Students have a bi-weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on reading textbook chapters and previewing a presentation on internal energy conservation.


Selected/edited responses are given below.

Describe what you understand from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically demonstrate your level of understanding.

"I understand the concepts of heating and cooling. I am a little confused on the conservation of energy and how that looks/is applied. I am also a little confused on the visual representation of heat flow."

"As molecules move closer together (condensation or freezing), potential energy decreases, or increases as they move father apart (vaporizing, melting). I understanding that heat flows from higher temperatures to cooler temperatures, and that in an insulated system, the decrease in the internal energy of one object is equal to the increase in internal energy of the object(s) it is transferring to."

"Heat is based on the movement of the atoms of an object. Fast being 'hot' and slow being 'cold.' Heat energy can be transferred between two items until they reach temperature equilibrium. Cooling down is a decrease in thermal internal energy and heating up is an increase in thermal internal energy."

"Thermal internal energy of an object depends on atom movement. So if an atom is moving faster, then the thermal internal energy must be higher. Whereas if the thermal internal energy is lower, the atoms move much slower if at all. "

"I understand that if you ignore external factors, much like our other energy transfer equations, you may zero out the left side of the equation."

"This section is just a review for me because I have taken chemistry where we have covered internal energy conservation and the multiple ways to find it."

"I understand the concepts of heating and cooling. I am a little confused on the conservation of energy and how that looks/is applied. I am also a little confused on the visual representation of heat flow."

"The systems are in thermal equilibrium if no heat flows between them when they are connected by a path permeable to heat. Thermal equilibrium obeys the zeroth law of equilibrium."

Describe what you found confusing from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically identify the concept(s) that you do not understand.

"I just covered this material with a student that I am tutoring for general chemistry so thermochemistry is all very fresh!"

"All and all it made sense. I took chemistry last semester so this stuff is very similar to what I have learned."

"This seems straightforward so far. Unsure of the exact relationship between temperature and thermal energy, though."

"Thermal energies can find equilibrium with the objects that it interacts with. How can we find the point of equilibrium between multiple objects?"

"I find the transfer of internal energy a little confusing. I could use some review on thermal energy vs. heat."

"I have a small issue in the difference between in temperature and internal energy and how they're related."

"I do not understand the equations given in this section. Like always, I will review more before class and then come in prepared."

"Honestly there wasn't a lot I didn't understand since I've seen this before."

Two objects that are brought into contact with each other will reach thermal equilibrium when they have the same:

internal energy.	*********** [11]
temperature.	************* [13]
(Both of the above choices.)	************** [14]
(Neither of the above choices.)	[0]
(Unsure/lost/guessing/help!)	** [2]

Raw seafood is placed on a block of salt that has already been heated up. The energy contained in the high-temperature block of salt is then transferred to the seafood, cooking it. While it is being cooked, the internal thermal energy of the seafood __________, while the thermal internal energy of the salt block __________.

increases; decreases.	*********************************** [35]
decreases; increases.	*** [3]
does not change; does not change.	* [1]
(Unsure/lost/guessing/help!)	* [1]

For the seafood cooking on the salt block (ignoring heat transfers with the environment), the object that experienced the greatest amount of change (increase or decrease) in thermal internal energy was the:

seafood.	************** [14]
salt block.	***** [5]
(There is a tie.)	******************* [19]
(Unsure/lost/guessing/help!)	** [2]

Frozen meat is placed in a water bath, in order to defrost it. At the very start of this defrosting process (where the frozen meat just begins to warm up from its below-freezing temperature, and the ice crystals inside have not yet reached the melting point), the internal thermal energy of the meat __________, while the thermal internal energy of the water __________.

increases; decreases.	******************************* [31]
decreases; increases.	******* [7]
does not change; does not change.	* [1]
(Unsure/lost/guessing/help!)	* [1]

For the frozen meat in the water bath (ignoring heat transfers with the environment), the object that experienced the greatest amount of change (increase or decrease) in thermal internal energy was the:

frozen meat.	********** [10]
water bath.	****** [6]
(There is a tie.)	********************* [21]
(Unsure/lost/guessing/help!)	*** [3]

A shot of whiskey is mixed with a pint of beer to make a boilermaker. Assuming that the whiskey and beer have approximately the same temperature before they are mixed together, the internal thermal energy of the whiskey __________, while the thermal internal energy of the beer __________.

increases; decreases.	[0]
decreases; increases.	***** [5]
does not change; does not change.	********************************* [33]
(Unsure/lost/guessing/help!)	** [2]

For the shot of whiskey being mixed with the pint of beer (ignoring heat transfers with the environment), the object that experienced the greatest amount of change (increase or decrease) in thermal internal energy was the:

shot of whiskey.	* [1]
pint of beer.	**** [4]
(There is a tie.)	******************************* [31]
(Unsure/lost/guessing/help!)	**** [4]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"I really like all the real-life examples you put in your lecture."

"I feel like this is the physics of cooking. Very cool."

"Whiskey/beer example review."

"Can you explain the whiskey/beer example in class, specifically what happens when two things are the same temperature?"

"Not sure how the whiskey/beer thing works. Is it a chemical reaction?"

"I have nothing interesting to add at the moment."