The original prac is in Biological Science, The Web of Life Teacher\u2019s Guide Part 2, Exercise 10b.4
\n1. Approx 25g agar (increase from 18g)
\n4g NaOH
\nDissolve NaOH in 100ml water.
\nHeat 900ml water in a beaker almost to boiling
\nAdd agar and continue boiling while stirring till dissolved. Allow to cool until temperature drops below 60C then add NaOH, still stirring.
\nAdd phenolphthalein until very deep pink \u2013 6 droppers full.
\nAllow to set then cut unto 1cm, 2cm and 3cm cubes, leaving some for cylinders.
\nDo NOT refrigerate (it fades). Can be made 2-3 days in advance if you take it out of container and leave loosely covered with plastic wrap on glass Petri dish and store in chemical store shelf.
\n2. Calculate amount of agar required to make gel at 1 cm, 2 cm & 3 cm deep
\nRecipe:
\nDissolve 18 g agar per litre in distilled water. Microwave in 1L beakers, with caution
\nAdd 4 g NaOH per litre after agar solution has cooled below 60C then add \u2013 phenolphthalein and pour into containers. Can last for 2 weeks in the fridge
\n3. We provided kits for students:-
\nKit set up in large plastic tray containing \u2013 500 ml 0.1M Sulphuric Acid
\n2 pairs gloves
\nplastic ruler
\nplastic spoon
\npaper towel
\nlarge crystallizing dishes. These make removing the agar blocks easier than using beakers which are much deeper.
\nknife
\nsmall white plastic dish for cubes of phenolphthalein agar -1 cm3, 2 cm3 & 3 cm3
\nTo make up 500mL of jelly for the cubes, weigh out 9g of agar and 2g solid NaOH. Dissolve the NaOH in 50mL of water. Heat 400mL of water in a beaker almost to boiling, add the agar and stir until dissolved. Allow to cool then, when the temperature falls below 60C, add the NaOH solution, stirring continuously, until the jelly is deep pink. Allow to set. The agar can then be cut into blocks of the appropriate sizes.
\n4. 36gm agar
\n1600ml water, enough for 24 groups with 1 x 3cm,1 x2 cm,1 x 1cm block each
\n9gm NaOH in 100mls water
\nPhenolphthalein in dropper bottles
\nMake agar with water & boil till dissolved until clear solution
\nDissolve NaOH in the water stirring constantly as this is exothermic
\nCool agar to 60 deg C then add NaOH soln \u2013 this is important
\nAdd phenolphthalein \u2013 a lot at first then drop by drop till agar is a deep pink colour
\nPour into containers to set. You can use the rectangular \u201cUnitray\u201d which has square corners.
\n5. 1800mL boiling water + 40g Agar, stir until dissolved
\nTurn hot plate off, but leave stirrer on and wait until it drops to less than 60oC.
\nMix 6g NaOH in 150mL water and add to above
\nSquirt in 200mL Phenolphthalein. Yes, 200mLs!
\nPour it into plastic dropper bottle trays, the \u201cUnitray\u201d. Leave overnight to set and the students then cut them to sizes
\n6. We changed the prac because the agar tends to fade. Make the cubes ahead of time. Students place them in 0.5% potassium permanganate solution for 5 minutes then slice as per the Student Prac book. It works really well.<\/p>\n","protected":false},"excerpt":{"rendered":"
The original prac is in Biological Science, The Web of Life Teacher\u2019s Guide Part 2, Exercise 10b.4 1. Approx 25g agar (increase from 18g) 4g NaOH Dissolve NaOH in 100ml water. Heat 900ml water in a beaker almost to boiling Add agar and continue boiling while stirring till dissolved. Allow to cool until temperature drops […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[4],"tags":[],"class_list":["post-261","post","type-post","status-publish","format-standard","hentry","category-experiments"],"_links":{"self":[{"href":"https:\/\/ciderhousetest.com\/labnetwest26\/wp-json\/wp\/v2\/posts\/261","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ciderhousetest.com\/labnetwest26\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ciderhousetest.com\/labnetwest26\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ciderhousetest.com\/labnetwest26\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ciderhousetest.com\/labnetwest26\/wp-json\/wp\/v2\/comments?post=261"}],"version-history":[{"count":0,"href":"https:\/\/ciderhousetest.com\/labnetwest26\/wp-json\/wp\/v2\/posts\/261\/revisions"}],"wp:attachment":[{"href":"https:\/\/ciderhousetest.com\/labnetwest26\/wp-json\/wp\/v2\/media?parent=261"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ciderhousetest.com\/labnetwest26\/wp-json\/wp\/v2\/categories?post=261"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ciderhousetest.com\/labnetwest26\/wp-json\/wp\/v2\/tags?post=261"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}