<p>Okay, I know this is a weird question, but I wanted to survey a bunch of science students for an opinion - </p>
<p>At what grade level is an average college bound but not necessarily science focused student introduced to Hess’s Law? What about an advanced kid? Would it be appropriate in an 8th grade classroom of average to high level students?</p>
<p>Thanks!</p>
<p>Trying to think back on the first class where I saw that, and I think it wasn’t until I took chemistry in high school.</p>
<p>Then again, science classes in my middle school were atrocious. I remember in eighth grade we were supposed to be doing earth sciences, but my teacher was a young-earth creationist. :(</p>
<p>The second semester of Gen Chem at my college covers thermodynamics so for students that don’t need the extra semester of preparatory chemistry based on their performance on the placement test their second semester of college.</p>
<p>Thanks guys - I have a parent teacher conference with son’s 8th grade science teacher who thinks it’s right on schedule for his class.</p>
<p>I don’t think it’s a terrible thing to introduce at that level. All you’re basically talking about is path independence. A simple analogy can be made with a ball rolling down a hill versus falling vertically (or a hill with multiple bumps). Either way the total change in energy should be the same (if there’s no friction). Or you could even talk about going up flights of stairs. There are some staircases that use larger stairs than others, but it doesn’t matter how many steps you take as long as the total change in height is the same.</p>
<p>What other sorts of things are you covering in this class that the parent thinks it’s appropriate to bring up Hess’s Law? Are you at PV=nRT and that sort of stuff?</p>
<p>I learned it in my first high school chemistry class (10th grade). 8th grade would be too early in my district - the students could barely balance chemical equations.</p>
<p>This was the test problem. They did 2-3 problems in class. No practice problems for home was given. I am not a science person - I’m just a mom (a teacher but not science), so I can’t make heads or tails of it.</p>
<p>Use the background information to calucate the heat of the reaction (deltaH) for C(s) + 1/2 o2 -> CO
Background information C(s) + 02 -> C02 deltaH = -393.5kJ
CO2 + 1/2 )2 ->CO2 deltaH = -283kJ</p>
<p>This question counted 16% of the test grade. Other thinks covered: specific heat calculations, calorimetry calculations, and the rest of the stuff was pretty standard (temperature scales, transfer or heat, endothermic vs. exothermic reactions).</p>
<p>I guess if the teacher just demonstrates it in class or has the students work in groups to solve problems like that it would be ok. I am assuming that the last equation you typed out is CO(g) + (1/2)O2(g) -> CO2(g) instead of what you posted. I would think that such a problem would be too difficult for middle school students - I don’t think many will see that if you flip the last equation the opposing (1/2)O2 and O2 results in (1/2)O2. People in my middle school (honors class, not standards) had trouble differentiating between protons, electrons and neutrons and the differences between atoms, ions, and isotopes, and this is at a much higher level. Hess’s law problems require algebraic reasoning, and only some middle school students even begin Algebra I in 8th grade.</p>
<p>Sorry I did mess up the last line, it should have read
CO + 1/2 O2 ->CO2</p>
<p>the g was not on the test. Maybe that’s understood? Again, I know nothing about this.</p>
<p>Anyway, thanks for the feedback. It reassures me that he knows what a bright 8th grader <em>should</em> know. I met with the teacher yesterday, and she knows it is advanced, but the science department apparently believes <em>all</em> students should be able to work at that level, and they “teach to the top”. It is a private school - he will be moving to a public school next year. I just wanted to have some reference of what he would typically be doing at this age. Thanks again for your help.</p>