Chemistry Demos Grade 11/12 Alex Foo –

Overview Slimes and polymers Shell Game (polyacrylate) “Hard Water” (aka: California snowballs) Glow in the dark chemiluminescence

Slimes and Polymers - Ingredients Slime 1: Polyvinyl alcohol Borax Water Slime 2: Sodium alginate Calcium lactate or any other calcium salt ebay - Amazon.ca -Fine food stores -Search under “Spherification”

Slimes and Polymers - Protocol Slime 1: Prepare 6% PVA solution in water Need to boil water to ensure complete dissolution Prepare saturated borax (4%) solution Combine 30 mL of PVA solution with 8 mL of borax. Add food colouring to taste Mix well to form a slime

Slimes and Polymers - Protocol Slime 2: Prepare a 0.75g/100mL solution of sodium alginate in distilled water Add food colouring to taste Prepare a 2g/100mL solution of calcium lactate in distilled water Pour 200mL of calcium solution into a clear beaker Add the sodium alginate solution slowly The alginate solution will polymerize instantly upon contact with the calcium solution, producing long polymer “nood;es” or “snakes”

Teaching notes: PVA polymerization: Long, linear polymers “cross linked” to form larger complex Increased number of intermolecular interactions results in change in physical properties

Teaching notes Alginate slime: Alginate contains acidic functional group Sodium forms charge-dipole interaction with a single acid group Divalent nature of calcium enables it to form charge-dipole interactions with two acid groups Resulting cross-links generate slime

Teaching notes - Applications in Biotech Beta-lactamase Enzyme responsible for antibiotic resistance in bacteria Breaks down beta-lactam class antibiotics (eg: penicillin) Active form is a dimer, with two divalent cations at the interface PDB ID: 1VAQ

Polyacrylate (shall game) - Protocol Polyacrylate powder (ebay) Water Cups Add water to polyacrylate and watch it disappear!

Polyacrylate (Shell game) – Teaching notes Polyacrylate contains many acidic functional groups Interact strongly with water, absorbing it in the process

Hard Water - Protocol Calcium acetate (ebay) Prepare saturated (~35g/50mL) solution in water Isopropanol Pour calcium acetate solution into a cup Add equal amounts of isopropanol Calcium acetate should precipitate out to form a gel

Hard Water – Teaching notes Calcium acetate highly soluble in water due to strong hydrogen bonding interactions Able to overcome Ca 2+ - CH 3 CHOO - ionic bond Isopropanol is less polar than water Reduced ability to form hydrogen bonds Ionic bonds re-form to produce solid Segue into solubilty, like dissolves like

Glow in the dark - Protocols Luminol (ebay) Fluorescein (optional – highlighter juice) Bleach Sodium hydroxide Water

Glow in the dark - Protocols Luminol (ebay) Fluorescein (optional – highlighter juice) Bleach Sodium hydroxide Solution A: Dissolve g luminol, 0.4 g NaOH in water. Add a pinch of fluorescein if desired Solution B: 1% bleach Chill, mix and watch!

Glow in the dark – Teaching notes Luminol is oxidized by the bleach to form a diacid Product initially contains an electron in the excited state Electron quickly relaxed, releasing light

Glow in the dark – Teaching notes Electrons on fluorescein absorb light emitted from luminol Become excited to higher energy level Slight loss of energy in the process Drop back down to release light of a different wavelength