Stevie D

Hello folks, As I think I mentioned in a previous post, I'm doing some science teaching at a local college. To achieve the unit descriptor for the module the students are working on, they need to, and I quote: "Investigate and explain the effects of one or more given factors, for example temperature, pH, substrate concentration or enzyme concentration on the functioning of enzymes." Should be easy enough. I want to run this practical, taken from the Nuffield Foundation website. That will hit the criterion for showing the effect of concentration on an enzyme-substrate based reaction. I will adapt the method to include a heated water bath to bring temperature into the equation in a separate practical run in the same session. However, for pH I'm not sure what to do. It would make life easy to use the above method, without the water bath or fluctuations in substrate-enzyme concentration and merely add acids / bases at a variety of pH values. In this similar method from the same website, it recommends sodium hydroxide at 0.25M. Do you think that will have a significant effect on a reaction involving 2cm3 of 10-30vol hydrogen peroxide vs. 20cm3 of (catalase containing) potato puree? If so, what volumes of bases (and acids) do you think I should use at these concentrations? Thanks for your time, Steve

Hi folks, I finished an Environmental Science degree in the summer of last year. I've since started a post-grad certificate which will enable me to teach. In my placement, I am currently teaching biology, chemistry and some maths bits and bobs the details of which aren't relevant here. I am going to introduce ionic bonds in a few weeks' time. I like to throw in plenty of practical work, because, well, best way to keep people engaged innit. So my initial thought was to do an electrolysis experiment. Graphite electrodes in a copper sulphate solution, that sort of thing. That said, the risk assessment / health and safety side of things could get messy, what with the copper sulphate toxicity and even a mild build up of sulphuric acid in the solution as the result of the reaction. The theory is a bit busy, too, given my (adult) learners' current level of understanding. So I'd rather keep it simple. I've been reading Raffan, J. and Ratcliff, B. (1995) Foundation Chemistry. Cambridge: University Press. On page 33 is a tidy little demonstration of ionic separation. I've attached a crude photo of the diagram to this post. I would like a cheap and cheerful practical demo, lasting no more than 30 minutes, where an ionic compound can be easily spread over a porous piece of card, like in the photo. My questions to you are: What type of card would you recommend, and what dimensions? What type of ionic compound, and how much? What voltage should be applied across the electrodes? Thanks for your time, Steve

That's the missing piece. Thanks for the reply.

Hi there. Writing a short piece in which I'm weighing up the viability of fusion power in the future compared with other, non-fossil fuel technologies. I've not dipped into fusion before, so I'm doing my best to get my head around it. I'm stuck on binding energy. My understanding is that mass gets converted into energy when nucleons combine to form a nucleus, as the result of the drop in mass. That's fine; here's where I get confused: An element like iron has a binding energy per nucleon which is higher than that of a much lighter atom, like helium. Since the binding energy in iron is relatively high, would that not mean there would be a greater disparity between the mass of an iron atom and the mass of its component nucleons in isolation? If that is the case, would there not be more energy release per nucleon when they combined to form the iron nuclide? If so, why is the focus on fusing the lightest elements in order to derive energy? Hope I explained it well enough. Thanks for your time. Steve

I see, thanks.

This is my first post here, so hello everyone. Making my foray into the wonderful world of science via an Access course (read A-level for mature students) in Marine and Environmental Science. See you at the lab in a few years' time. Anyway, onto the question. Working away on a biochemistry module at the moment (RH5/3/WW/003). Trying to rationalise to myself the formation of sucrose from glucose and fructose, as you may have determined from the thread title. I found this website: http://dl.clackamas.edu/ch106-07/sucrose.htm What I don't understand is their explantion of how b-D-fructose in standard orientation, shown here: ...gets flipped to b-D-fructose in inverted orientation: Are these two separate isomers? I've tried mentally rotating the first molecule in all three dimensions but still can't find a way to do it so that it ends up looking like the second one. I'd appreciate an explanation by more learned people. Cheers, Steve