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 heat and internal energy and that heat tends to flow from a hotter temperature object to a lower temperature object."
"If something's thermal energy increases, the temperature increases. If the thermal energy decreases, the temperature decreases."
"I understood a lot because I learned this in chemistry. Heat always flows from high to low, if the environment has no effect then each energy term must directly mirror the other..."
"If the thermal energy of a system is increasing (heating), that means external heat is positive and is adding into the system. If it's decreasing (cooling), external heat is negative and it's removing from the system. Zero means no energy is being transferred in or out of the thermal internal energy system."
"Thermal internal energy depends on temperature. It makes sense that a low temperature object has low thermal internal energy, and a higher temperature indicates higher thermal internal energy. Energy not transferred in/out of the thermal internal energy of a system is isolated from the environment and heat exchange between the system and the external environment is zero."
"Thermal energy is transmittable between objects in the form of heat. Temperature changes are a direct result transferences of proportionate amounts of thermal energy. It is also worth noting that different materials are able to retain and transfer thermal energy very differently."
"I understand that when we look at thermal internal energy we are more focused on the change in temperature of an object or objects. Everything has its own specific heat capacity similar to last chapter when we were talking about the Young's modulus. Heat is added to a system or taken away from a system and that energy is conserved in thermally isolated areas. However, perfect thermally isolated areas do not appear often in the natural environment but we can create those in things like a thermos (still not perfect)."
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 don't understand how internal energy and temperature relate to each other."
"I understand the heat and energy concepts. I am confused about using the equations. I will pay attention in class and keep on visiting the tutors."
"New symbols/terms for these things are going to take some getting used to."
"Simple concepts in this reading. Not too much that is confusing."
"Nothing too confusing from this reading thus far."
Two objects that are brought into contact with each other will reach thermal equilibrium when they have the same:
internal energy. ******** [8] temperature. *************** [15] (Both of the above choices.) ************* [13] (Neither of the above choices.) [0] (Unsure/lost/guessing/help!) *** [3]
increases; decreases. ************************************ [36] decreases; increases. * [1] 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. ************* [13] salt block. * [1] (There is a tie.) *************************** [22] (Unsure/lost/guessing/help!) *** [3]
increases; decreases. ******************************* [31] decreases; increases. ** [2] does not change; does not change. **** [4] (Unsure/lost/guessing/help!) ** [2]
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. ******** [8] water bath. ******* [7] (There is a tie.) ********************* [21] (Unsure/lost/guessing/help!) *** [3]
increases; decreases. [0] decreases; increases. * [1] does not change; does not change. ************************************ [36] (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. ** [2] (There is a tie.) ********************************* [33] (Unsure/lost/guessing/help!) *** [3]
Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"I'm pretty sure that the salt block and seafood experience the same amount of change in internal energy, but if the salt block is bigger in size than the seafood that is being placed on it or if the difference in temperature is extreme (the salt block is fresh out of the oven and the seafood is frozen), wouldn't the seafood experience a greater change in internal thermal energy than the seafood? Also wouldn't the salt block have the least amount of change due to the fact that it is has more mass than the seafood?" (Yes, both the salt block and the seafood would experience the same amount of change--if the seafood gains 10,000 J, then the salt block must have lost 10,000 J (if we can neglect heat exchanged with the environment). Even if the salt block and seafood temperatures are very different, they will still undergo the same decrease/increase in internal energy. However, due to their different masses and different heat capacities, they will experience different temperature changes; typically the salt block will only "cool down a little" (experience a small temperature decrease) while the seafood will "heat up a lot" (experience a large temperature increase) despite experiencing the same amount of change (decrease/increase) in internal energy.)
"I am not exactly sure about whiskey-beer questions. If both have the same temperature prior to mixing, then there should not be a change in their thermal internal energies?" (Yes.)
"I understand that the change in thermal energies is equal for two objects interacting (only with each other, and not with the environment) and have reached thermal equilibrium. But does that mean they should have the same final temperature?" (Yes, the definition of thermal equilibrium means that the two objects have the same final temperature. Since heat flows from a hotter object to a cooler object, once the two objects have reached the same final temperature, then the exchange of heat stops.)
"Thermal energy transfers happen all around us everyday!"
"I never thought I'd see Q = m·c·ΔT outside of chemistry :/" (We're going over it here in physics, because I don't think chemistry truly covers the nuances of that equation.)
"Hope you had a great Thanksgiving?" (Eh, it was okay. I'm fine with okay; for me okay is pretty awesome. How was your Thanksgiving?)
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