Session details: Science Biology Tuesday, 27 January :13PM

Transcription

1 Session details: Science Biology Tuesday, 27 January :13PM Level of help the student selected: Start from the beginning Student question: Evaluate the effectiveness of quarantine in preventing the spread of plant and animal diseases ACROSS REGIONS of Australia, use one plant and animal example. Hi, I'm Tutor, your tutor. Hi, I'd like help with the question above please :) Good question, what do you have so far? so i was thinking to talk about quarantine stations across each entry point for each region and my examples I'd be using is fruit flies and the equine influenza so the measures i have is isolation, quarantine, isolation, fumigating but the effectiveness of it, I'm not too sure, i was going to say that it is effective When it comes to evaluating whether something is effective you basically need to point to your evidence of when it has worked or failed like the equine influenza for example, they had signs and electric signs above motorways to warn of the influenza and areas to avoid so restricted areas yep So you either say it is or isn't effective and describe the reasons why, citing your evidence yep, okay so

2 say if i used the example above I'd say it is effective because it prevented the spread of equine to other horses across regions Yep, that's the right idea in my answer, would i have to state an example and talk about one being effective and one not being effective? or would i just state a measure and say its effective to validate my point If you have conflicting evidence you can say that it's effective in some cases but not all, it's best not to cut out evidence, so if you found cases where it didn't work it's probably a good idea to mention them okay cool, thanks so much for the help today :)

3 Session details: Science Biology Thursday, 05 February :09PM Level of help the student selected: Revise a concept Student question: we did an experiment where we cut up pieces of beetroot and put them in distilled water, the high concentration of distilled water goes into the cell but does this cause the cell membrane to break? Hi, I'm Tutor, your tutor. hello Good question, what do you think would happen? I think it would cause the cell to burst Is that what you observed in the experiment? I'll need you to draw a quick scribble on the board so I know this session is active, okay? we were looking at the difference between that experiment and what happens if detergent is used and the red pigment caused the water to go red with the detergent Did you observe anything to indicate the cells were bursting when distilled water? no just the leaking of the red pigment Right, what do plant cells have outside their membranes?

4 cell wall Yep, what does a cell wall do? so it probably wouldn't burst along with the vacuoles That's right, plant cells don't burst when put into distilled water because the cell walls hold them together Does that make sense to you? okay, that makes sense. so in the experiment with just the distilled water, the water had a tint of red but was still very much transparent how would i explain this in regards to cell membrane? Where did the pigment come from? within the cell Okay, if the pigment wound up in the water what must have happened? I was thinking because it was only minimal that it has leaked from the cells that have been cut How large were the pieces of beetroot and how long were they in the distilled water for? 48 hours and it was one slice cut like a pizza into 5 pieces slice was only a few mm thick If it was left for that long you're probably right that it was just pigment on the surface. Did the beetroot change in colour in that time? not really, there were a few very small areas where there seemed to have lost all colour but on the whole no

5 If it stayed roughly the same you can probably assume the pigment in the water was just from the surface then and that the pigment can't make it through the cell membrane okay thank you You're welcome, would you like help with anything else? sure, why does detergent emulsify membranes? i don't really understand how it affects the fatty acid tail Well, what is the structure of detergent? detergent? I have no idea The structure of detergent is pretty similar to the structure of the lipids in the membrane So they look something like this: issue 3/v3 3 figure 1.gif The hydrophobic part of the tail happily interacts with the tail of the lipids and the hydrophilic part interacts with the water Does that make sense so far? yes so it sits in between the phospholipids? Yep, and then it disrupts the structure of the membrane and results in the formulation of droplets of hydrophobic tails surrounded by water, making the emulsion ahh okay I half understood before Great, does it all make a bit more sense now? Sure does thank you You're welcome, have a good evening :)

6 Session details: Science Chemistry Monday, 16 February :07PM Level of help the student selected: Start from the beginning Student question: Writing a balanced chemical equation for the following reactions Hi, I'm Tutor, your tutor. Hello I'm not too sure how to write "Solutions of sulphuric acid (HDSO4) and barium hydroxide form a barium sulphate precipitate and water Okay, let's see if we can write a balanced equation. First of all, do you know what the D means in HDSO4? Oh sorry I meant H2SO4*** Okay, that's fine. Alright, then how should we start? Um finding the symbols of each of the elements? Cool, how would we write barium hydroxide? um Ba with a charge of 2+ and OH1

7 Cool, so if we write this as a compound, what would it look like? For example, sodium chloride (Na+ and Cl ) is written as NaCl. BaOH2 I think? Not too sure! That's really good! Just one small thing, we need to put brackets in. The 2 refers to both the O and the H, and to note that, we write Ba(OH)2. Otherwise it looks like we have 1 O and 2 H's. Does that make sense? OHHHH YES!! omg thats why i always wondered why thank you haha!! That's great, it's a small detail, but it is very important. Okay, next. What is the formula for a sulfate ion? Um how come we're finding the sulfate ion? We're going to use it to write the formula of barium sulfate. Oh isn't it sulphate Is it the same thing? Yeah sulfate and sulphate mean the same thing. Just different ways of spelling. You will find that sulphate is the old fashioned spelling, but that's another story. Ahhhh okay! Would sulfur be the sulfate ion? Not quite, the sulfate ion is SO4 2

8 ooooh Iokay okay So, what would the formula for barium sulfate look like, given that the barium ion is Ba 2+. Um Ba4(SO2)2 Okay almost, I see that you have the right process, but just one thing. I think you used SO2 with a charge of 4 instead of SO4 with a charge of 2. Oh I think so um Would it just be BaSO4? Perfect! Yay :) Okay, I'm going to write out the word equation you gave on the whiteboard, and underneath, you can go ahead and write the symbol equation. Okay! Okay, all yours. Okay One question what is sulfuric acid its not on my databooklet Sulfuric acid (sulphuric acid) is given in the question as H2SO4

9 ohokay, silly me haha No worries! Only one thing missing, scroll back up and see if you can spot it. is it the charges? Nope, but it sort of has something to do with that. Remember, barium hydroxide is Ba 2+ and OH. So when they form a compound, we write it as... Ba(OH)2 Yes! Ohokay great!! So fix that up, and we will balance the equation, and then we are done. ohokay, i can balance the equation myself, but thanks a lot!!!! :) Awesome, would you like to quickly do that on the whiteboard? Or would you rather do that on your own? Ummm Could we quickly do it on the whiteboard? :) Absolutely. Can you fix the BaOH into Ba(OH)2 Cool, and lastly, go ahead and balance. Okie um Could I do it on my sheet then check with you? :) Yes that's fine

10 Oh Do we just add a 2 onto the last bit The H2O bit? Yep, that's it. Perfect! Ohokay, yay! thank you very much!!! :) was very helpful lesson! No worries! If you have anymore questions, please log back in and a tutor will be with you shortly :)

11 Session details: Science Chemistry Monday, 16 February :57PM Type of help the student selected: Start from the beginning Student question: Thin layer chromatography showed that the black dye used in a brand of writing ink contained blue, red, orange and yellow components. The Rf values of these substances Hi, I'm Tutor, your tutor. Thin layer chromatography showed that the black dye used in a brand of writing ink contained blue, red, orange and yellow components. The Rf values of these substances using ethanol as the solvent are 0.59, 0.32, 0.80 and 0.19, respectively. a How far apart would the blue and yellow components be after the solvent front had moved 8.0 cm from the origin? b When the red component had travelled 6.0 cm from the origin, how far would the orange component have travelled? c Sketch the chromatogram of the ink to scale after the solvent front had moved 15 cm from the origin. hello. Any ideas on how to approach this question? okay soo would it be like 0.59 = x/9.0 cause we need to find the distance moved from the origin Where does the 9.0 come from? that wouoh sorry i meant 0.59= x/8.0

12 that would be the distance moved by the blue component No worries! That's right! okay cool so you can find the yellow one too, in the same way and then just subtract the values to know how far each of them are apart Good! That's right. what about part b? We have to use the formula in reverse here. I'll write the general equation. okay, so we know how much the red component moved and the distance moved by the solvent would be the same as in part a? yes please, thanks. Because parts 'a' and 'b' are separate, we ignore any information given in part a. alright! :) We'll call the numerator 'x' and 'y' because its quicker to type! sure! So for part b, what is the 6cm? Is that x or y? that would be the x Good! What is the Rf value for the red component? from the question its, 0..32

13 That's right! so we can fin y! Good! This will give us how far the solvent has moved. okayy so if we know how far the solvent has moved, and we know the rf for the orange component we can find the distance moved That's right! okay! I get it now! thanks a lot, have a good night. You too! :) Bye!