Determine whether each process is exothermic or endothermic
and i...

Question

Determine whether each process is exothermic or endothermic
and indicate the sign of ΔH.
a. natural gas burning on a stove
b. isopropyl alcohol evaporating from skin
c. water condensing from steam
Determine whether each of the following is exothermic or endothermic.

Accepted Answer

Welcome back everyone. We need to identify either of the processes as endo thermic or exit thermic, let's begin by recalling what an exit thermic process entails, recall that it involves the loss of energy bonds breaking and overall a net negative entropy change. Recall that Delta H. Represents our symbol for change, which represents the heat content of a system and it makes sense that we have a negative sign since we know we're losing energy in an exit thermic process. Now let's begin by recalling what an endo thermic process entails. So it's going to be the opposite where we would have a gain of energy or energy required. We would have bonds formed and we would have a net positive entropy change since our system requires energy. So let's begin with our first scenario which is scenario a the formation of morning dew on plants, we're going to imagine a leaf and I'll draw the dew droplets on our leaf which are these blue circles recognize that these do droplets are made up of liquid water. However, they are condensed onto the leaf from the result of water vapor in the air. So water in gaseous form condensing onto our leaf which has a cooler surface which creates these dew drops. And so we can understand that our water vapor is at a much higher temperature where again the surface of the leaf is a cooler temperature and through this process we've described as condensation, we have the release of heat again to the plant surface. Since this specifically this process involves the release of energy we would say that therefore we have a negative net entropy change, meaning that this is an X. A. Thermic process. Now recognize in this case we don't necessarily have bonds being broken. What really is occurring is the inter molecular forces are strengthening through the process of condensation where they overcome the kinetic energy of water in its gaseous form and the molecules then stick together to become water in its liquid form. So overall, let's confirm that for choice. A Our answer is going to be that formation of morning dew on plants is an exact thermic process. Now let's move on to example B, which considers burning wood. So we're going to imagine a slab of wood, it's on fire. And what we have going on here is actually a reaction between our wood and oxygen in our air. So while this reaction occurs, the bonds in the wood are breaking while bonds are being formed with oxygen in the air. And we have the falling combustion products where we would form water vapor, carbon dioxide, gas and other combustion products. Recognize that through this process of combustion, we have the release of heat and light to the environment. And while we would observe a bit of endo thermic process in vaporizing any water molecules present in our wood, the net endo thermic effect of that is actually negligible in comparison to the overall entropy change of our combustion, which again releases heat and light. And so therefore we would have a net negative entropy change for this combustion. And so therefore this process burning wood is exo thermic and this is our second answer for part B. Now, let's consider scenario C, which is the formation of dry ice fog. So for this example, let's visualize a slab of solid. So this is our solid carbon dioxide and we should recognize this slab as a piece of dry ice. We can imagine it being inside of a container filled with hot water sitting on a hot plate, which is heating our container of hot water. And as a result, what we would observe is that the dry ice instantly will sublime into a gaseous form, creating a fog. So we have carbon dioxide in a gaseous form and this is our dry ice fog. Now recognize that dry ice fog is extremely dangerous and it should be handled with care, so or rather not the fog but the dry ice itself. So you need special appliances. But once the fog is created, what it's going to do is instantly lower the temperature of anything surrounding. And so in this case our surroundings temperature is going to decrease, creating cooler conditions. But the key thing to recognize here is that we have a hotplate heating up our system. And so that means that this reaction between solid carbon dioxide forming carbon dioxide gas will require heat and recall that we represent an addition of heat and reactions by a delta side Over our reaction arrow note that I use the words sublime. What I'm describing is the process of sublimation, which is what is occurring here when a solid becomes a gas and it becomes a gas without going through the liquid phase specifically. And so we require energy for this process. And since our system being our reaction requires an input of energy in the form of heat, we would say that therefore this process is endo thermic and this would be our answer for part C of this example. So everything highlighted in yellow represents our three answers for each of the scenarios that were given scenario. A formation of morning dew on plants is exo thermic scenario be burning wood is exo thermic and scenario C formation of dry ice fog is an endo thermic process via sublimation. All of our answers we outlined correspond to choice C in the multiple choice. So I hope this was helpful and let us know if you have any questions

Determine whether each process is exothermic or endothermic and indicate the sign of ΔH. a. natural gas burning on a stove b. isopropyl alcohol evaporating from skin c. water condensing from steam Determine whether each of the following is exothermic or endothermic.

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