Stain removal year 11 prac

[lesley]

I am hoping anyone can help in a practical investigation for a Year 11 practical.

EFFECTIVENESS OF SOLID OXYGEN BLEACH IN STAIN REMOVAL.- Stage 1 Chemistry task AT1-Investiagtions Folio - Task 1

The Teacher who has not taken Chemistry in a few years wants to use liquid bleach brought from the supermarket in dropper bottles.

Making temperature the variable. I have suggested changing concentrations but this is not how she wants to go.

As this is a new practical , any suggestions would be helpful for her in guiding students.

Otherwise I will just give her what she asks for and hope for the best .

Regards Lesley

[Jazz]

I would not recommend to heat bleach, See manufacturer's SDS sheet section 10. STABILITY AND REACTIVITY
she could try
different water temperature using solid bleach (bleach stick)
use different materials with same bleach
same material different bleach
same material same bleach different stains
Check your PM

[lesley]

Thanks giving her hot plates to heat water , then the student will add drops of liquid household bleach from the dropper bottle.
Wants a variety of different temperatures. ie ice water , room temp and 3 heated.
Using same material and stain .
I do not think the household bleach will be strong enough , or how much they need too add. However as long as same amount is added to each sample.

[linotas]

Household bleach is generally 5% sodium hypochlorite. Diluting it in a beaker of water seems a waste. A quick google reveals that heating up to 60 degrees has been studies a lot. SDS doesn't say it can't be heated. I'd be doing some more investigating before doing it if I was the teacher. One thing I wouldn't let them change the pH. Changes liberate more or less Cl2....could be nasty

[Rock]

Wouldn't this prac be referring to the Napisan type bleaches? They are supposed to work best in warm water. There are liquid forms available.

[lesley]

The practical did not work that well (as I expected) but that was okay.

Lots of ideas from students on how to do it next year . The Teacher was happy with the results and the discussion as to why it did not work.

PS I retire at end of this school year..so I will leave a list for my replacement.

[Lyn]

Have just read the background information on this prac and it calls for the use of solid oxygen bleach which is sodium percarbonate. Basically the ingredient that is in products like Napisan or the Coles or Woolies nappy treatment, which are far cheaper than Napisan. As yet my chem teacher has not gotten to this prac but when she does I will be providing the solid bleach in the nappy treatment product. The students can make up their own solutions from the solid form.

(Famous last words - she will probably want the liquid bleach with the sodium hypochlorite instead.)