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Open night coming up, and one teacher has suggested something he'd done elsewhere - something about putting flowers in a vase of universal indicator solution & leaving them for ??? how long. Then you spray the flowers with an acid or base, and the petals change colour. Apparently reversible if alternate the sprays. Sounds rather neat! Of course all the preparation had been done for him, so he was able to describe the doing, but not the getting ready.
I'm about to experiment - white flowers, full strength universal, vinegar & bicarb sprays, but was wondering if anyone out there has done this, and had any info on times, solutions & strengths, best flowers to use..... any ideas will be much appreciated
I tried picking some Hydranger flowers and putting 1 in 0.1M HCl and the other in 0.1M NaOH the hydrangers were a white varity I had growing, the one in acid developed slight pink spots overnight the other developed slight blue viens in petels, but over all not a success!!
I have used white agapanthas in food colouring, I split the stem into four and put each bit in a separate food colour. It takes a couple of days to get the colour change in the petals so in answer to the first question (how long should the flowers be in universal indicator) I would say at least 2 days. It sounds like a great idea using the universal indicator and then spraying with an acid and a base. I hope it works well and when I find some white flowers I'm going to give it a go.
As a sort of variation on spraying the petals, here's one my Dad (Prof Botany ANU) did years ago with Hydrangeas. Dolomite added makes blue flowers, and Urea makes pink. Yellow can be achieved with a bit of tweaking to get it near neutral.That's why buying coloured Hydrangeas is such a joke. They are often sold as pink or blue, but that's just literally an indication of how the soil has been treated.
I guess it all depends on how quick the plant(/flower) sucks up the liquid and the ability of the indicator to move through the plant's xylem. If this is possible, as it seems from the teacher, I would be looking at flowers that don't have any great adaptations to water loss, so avoid waxy flowers. Maybe try chrysanthemums (plenty available at the moment) or carnations, flowers that are quite soft in texture. Any of the annual flowers would probably work well too - they are notoriously thirsty plants.
I'd suggest cutting the stems just before putting them into the liquid, you'll achive better uptake of the liquid. The rate of transpiration will depend on the environment - if you have a cold prep room (like mine) the water movement will be much slower in the plant than if it was in an air conditioned room. Try it after 24 hours. Any longer I would be concerned about possible detrimental effects of the indicator on the plant, just keep an eye on the flowers for any wilting or browning off.
Sounds like a great bit of science "magic" - the younger kids would love it.
Update: Potato vine flowers in full strength universal overnight - looked very unhealthy this morning, and no colour change with spraying. [I was wondering about how it was supposed to work with the indicator being within the cells, and the spray on the surface.] Checked with teacher, and he reckons that yes they were real floweres he'd used previously. Might buy a bunch of flowers Mon morning to try again, 'cause I've exhausted my supply of garden flowers. Not much flowering this time of year in Canberra!
Have tried a google search - can't find anything with real flowers, but did find one reference to making paper flowers & dipping in indicator, allow to dry, then spray. Has potential, but I'm not too sure about making & drying lots of paper flowers by next Tues night, not to mention visions of soggy tissue flowers left round other faculty displays. How to make Science popular with the rest of the staff!
Pity - it did sound good. Maybe next year.............
Hi
we use white carnations. They work really well, gets results within a few hours. we also split the stems up to 5 ways and put each bit in a test tube of food colouring.
Yes I've done that with white jonquils. You know the smelly ones - you either love them or hate them. I love them - could fill my house with them but my husband and daughter hate them. They work beautifully and when you split the stem and put them in separate colours, very nice! It works quickly and they last for ages.
J
cecmel wrote:Update: Potato vine flowers in full strength universal overnight - looked very unhealthy this morning, and no colour change with spraying. [I was wondering about how it was supposed to work with the indicator being within the cells, and the spray on the surface.] Checked with teacher, and he reckons that yes they were real floweres he'd used previously. Might buy a bunch of flowers Mon morning to try again, 'cause I've exhausted my supply of garden flowers. Not much flowering this time of year in Canberra!
Have tried a google search - can't find anything with real flowers, but did find one reference to making paper flowers & dipping in indicator, allow to dry, then spray. Has potential, but I'm not too sure about making & drying lots of paper flowers by next Tues night, not to mention visions of soggy tissue flowers left round other faculty displays. How to make Science popular with the rest of the staff!
Pity - it did sound good. Maybe next year.............
I had thought about how much the indicator would make it's way up and out of the plant. As a thought, what happens when you just spray the indicator onto the flowers before the acid and base?
This sounded so fun I thought I'd have a go. Left some flowers in universal indicator over night. This morning I took a couple of petals off and dropped acid / base on them and left them for awhile. They have definately changed colour - NaOH = yellow, HCL + red. I had two types of flowers. The white geranium did not work as well as the other flower which I don't know the name of.... It is a vine, whitish petals with dark pink centre (I'll try to find out the name). so the experiment has possiblities - just needs some refining.
kathryn
Thanks Kathryn & you others! I've been waiting to see what you clever lot would come up with. When I finally get my hands on some white flowers I'm going to have a try too!
Cecmel - I saw that one with the tissues & indicators too... sounds good in theory but I agree with you.. messy! I wonder if normal paper would work better? Let it soak in the UI & then dry overnite before spraying?? You could call it - magic paper or get the kids to make something origami-ish out of them & then spray with acid or base...?? Just (probably poor!) thoughts.
It would be great to get the fresh flowers working though!!
Finally got some cheap white jonquils and some time to play. Used half strength and full strength Universal, also Phenylphthalein, and sprayed after 4 hours and overnight, using vinegar, sodium bicarb, and household ammonia. Results were blah - nothing happened. Also tried dipping the flowers in indicator solution, and letting them dry, then spraying - got a few coloured droplets on the petals - again, nothing worth reporting. In the words of the MythBusters, I reckon "BUSTED".
I've also tried with paper and tissue "flowers" dipped in indicator solutions, and that has potential. Get a colour change when spraying with all three solutions. The colour produced with bicarb stays, but fades with drying for both vinegar and ammonia.
Teacher still reckons they were real flowers he used, and said he'd contact his Labbie (in Hong Kong) to double check. I'm reckoning they were probably artifical flowers, and it's so long ago that he did it, that he's forgotten that detail!
Oh well -it's one of the fun things in this job - getting to muck around with stuff like this. Maybe I'll try to get hold of some cheap fabric flowers before next year, and continue to experiment!
This sounded like fun so I had a play yesterday.....I soaked some filter paper circles in universal indicator then dried them my glassware dryer, soaked them a second time & dried again to get a nice dark colour. Actually comes out orange on the paper, not green.
I folded the circles into rough flowers & sprayed with vinegar - nice change to red, then ammonia- change to purple. You can get the colour changes to go back & forth a couple of times, but you have to soak the paper with the solution & wait a few seconds for the colour to develop.
It's not exactly fireworks, but it's kind of cool. Like vclabbie said, it would be great for the younger kids to do. You can give them the pre-soaked paper & they make the shapes.
I might get some fake flowers from a $2 shop next & try that.
I wonder if hydrangea flowers - you know the ones that are blue in acid soil / pink in basic... or is it the other way around?! - would work? I'm assuming the acidity / basicity stays in the flowers though......... Don't suppose you could spray with both acid & base though... Just thoughts... random...
Yesterday I went to the $2 shop down the road & found a bunch of fake white flowers. It's a posie so there are 6 flowers all joined on the one stem.
I did the same as with the filter paper. Soaked in universal, dried in the drying cabinet, soaked & dried twice more to get good colour depth.
They work a treat & it's visually a lot of fun because you can separate the flowers out by bending the wire stems apart a bit, & spray with the ammonia & vinegar from a bit of a distance so you get speckles of purple & red, or spray individual flowers to completely colour them. You can get the colour reversal by alternating sprays 2 or 3 times, but it ends up dripping everywhere so best done in a tray. I imagine I can wash & reuse the flowers because the fabric feels quite strong & they've withstood the soaking & spraying & haven't fallen apart yet.
- could fill my house with them but my husband and daughter hate them. 
They work beautifully and when you split the stem and put them in separate colours, very nice! It works quickly and they last for ages.
