Penolphthalein Agar Prac

[shaz.H]

Hello everyone,
I have always prepared Phenolphthalein agar cubes for Year 11 Biology, one of my science teachers has asked for this practical for Year 8 !, just wondering if anyone has ever prepared this practical for any year other than year 11 before?
shaz

[dime]

No, only year 11 Bio, for 22 years

[superbug]

yr 11 bio only so far, but I cant see why year 8 can not do the prac, as the chemicals used are ok to be used by yr 7 to 12.

[MariaC]

The only thing is if they do it in year 8, its not new in yr 11, plus if all of year 8 do it that would be an extra cost, is it necessary? Just my thoughts. MariaC

[superbug]

Not all students do biology in their senior years.

[smiley]

Its part of the new Australian Curriculum, and belongs in the understanding cells part of their learning.

I used the PERFECT recipe from this site, and pre-cut the cubes so that no-one was playing with blades. BTW, if you save all those offcuts, and melt them carefully, then this agar is re-usable up to a point. (as in - not the diffused cubes, but the other bits).

[sunray18]

I tried the perfect recipe and it did not set.

[smiley]

Well check all the chat about a batch of agar not setting. It might be that!

[Ocker]

Yeah! Smiley
I always chopped up left over gel real fine then put in microwave for about 20 seconds first then 10 secs at a time depending on amount but you can get a feel forit and add extra Na OH if necessary as it fases in acid atmosphere!

[Mags]

HI There I was wondering what the Perfect recipe which you were referring to and where I could please get a copy.
Thank you

[smiley]

Well I know it exists on this site, but here it is again. I didn't write it but I have used it and it's great!

PINK/PHENOLPHTHALEIN AGAR BLOCKS

For 1 block (10 dropper tray, divider removed)

14.4g agar
480ml water
24ml 1M NaOH
4.8 ml phenolphthalein

Put agar in beaker, add water and magnetic stirrer. Full heat, stir to dissolve. Remove stirrer, continue heating till boiled. Remove from heat. Add NaOH and phenolphthalein. Pour into tray, allow to set.

[dime]

May I just add,I found that it does work best if you let the Agar cool down to 60deg C before adding the NaOH and phenolphthalein.