3 fun and slightly messy experiments to complete in a 1hr session to complete the Beavers Experiment Badge: (i) Baking powder + vinegar (Chemical reactions); (ii) Felt tip pen ink spots (Chromatography); (iii) Cornflour + water (Non-Newtonian liquids). Experiments (i) and (iii) should be run outside. Session was based on 15 Beavers, split into 3 groups, rotating around each experiment
(Based on 15 Beavers)
Experiment #1 - Baking powder + vinegar: small water bottles (with label and plastic ring removed), balloons (pre-stretched), 3x 570ml vinegar in 3 containers (ice cold, room temp, warm), 2x 170g baking powder, funnels (for dry and for wet ingredients), containers for vinegar, ice cubes and microwave / thermos, measuring spoons
Experiment #2 - Felt tip pen ink spots: Lots of (water-based) felt tip pens, kitchen roll, scissors, pegs, plastic cups, 2l bottle of water
Experiment #3 - cornflour + water: 2x 500g cornflour and container, water and container, mixing containers for Beavers, food colouring, spoons & stirring sticks, plastic plates with high rim, bin to dispose of flour mixture, measuring cups, extra bowl, sandwich bags, eggs, wipes!!!
Experiment #1 - Baking powder + vinegar (Chemical reactions)
* Instructions: fill water bottles about third full with one of the vinegar containers; fill balloons about half full with baking powder; attach balloon to neck of bottle without spilling baking powder; wait till everyone is ready; everyone tips up balloon to mix baking powder with vinegar; balloon inflates; watch what happens to the balloons and how fast they change
* Questions to ask: what happened when you mixed the vinegar and baking powder? what's in the balloon? what do the bubbles mean? are the balloons the same size? which one filled faster?
* Learning: combining acid (vinega) and alkali (bicarbonate of soda) makes a chemical reaction that produces (a salt and) carbon dioxide gas; CO2 has nowhere to go other than to expand the balloon; hot / cold temperatures mean vinegar molecules are more / less excited and are more / less likely to meet with the baking powder molecules so reaction is faster / slower and balloon fills faster / slower; (could also try with more / less baking powder to see what this does to balloon size)
* Safety: keep vinegar away from eyes, do not over-fill bottles, balloon may pop making a mess
* Demonstration: https://www.youtube.com/watch?v=6usyUfhXDSg
* Info sheet: http://www.rigb.org/docs/fizzycubes_infosheet_1.pdf
* Instructions for resetting experiment: rinse and reuse water bottles; stretch new balloons
Experiment #2 - Felt tip pen ink spots (Chromatography)
* Instructions: Put about 1cm of water in the bottom of the cups; cut kitchen roll into strips; make a ink dot about 2cm from the bottom of the paper strip (brown and black pens better, but each should pick a different one); dip the end of the kitchen roll into the water with the dot just above the waterline; fold over the paper and use the peg to secure the paper to the cup; as the paper absorbs water upwards the ink dye is dissolved and is carried upwards too making colourful patterns; repeat with other colours; (alternatively pre-prepare some dots with pens the children have already used and get them to deduce which pen it was from the colour pattern)
* Questions to ask: what happened to the water and the paper? what happened to the dots? do they stay the same colour? do all the colours move the same distance? which pen dots have the most colours in them? which colours move fastest? do you think you could work out what pen had been used from the pattern you can see?
* Learning: Some pens use lots of dyes mixed together, each component of which is slightly more / less soluble than the others and travels relatively further / less distance with the water in any time period and spreads out over the paper; darker colours mix more dyes and causes the biggest patterns; recognising the pattern can help identify which pen is being used
* Safety: take care with the scissors
* Demonstration: https://www.youtube.com/watch?v=qV4vaqQEz5c
* Instructions for resetting experiment: n/a
Experiment #3 - cornflour + water (Non-Newtonian liquids)
* Instructions: carefully measure 80-100ml of water and add cornflour spoonful by spoonful in to the bowl, mixing all the flour in as you go (this is tough, time consuming and possibly messy!); should end up with a mixture like honey but carefully add small bits of water or cornflour and mix again to get consistency right; play with the mixture in the bowl and then pour into the plate to play with it there; (optional) add a few drops of food colouring to see how it mixes; (optional) have another bowl or plate of water to compare properties; (optional) pour the mixture into a sandwich bag and seal a raw egg inside before throwing high in the air to see if the mixture will protect it... (n.b. this worked for me only once out of two attempts!)
* Questions to ask: do you know what a liquid is and what a solid is? In a bowl: what do you notice about the liquid? what happens if you poke / stir it slowly / fast? On a plate: what happens if you grab it slowly / fast? what happens if you slap the mixture hard? what happens if you try to stir in food colouring? (Optional) what do you think would have happened if the happened to the egg was in water? what happened to this egg!?!
* Learning: normally we talk about things either being solid, liquid or gas. This mixture is different, it's called a 'suspension' and acts as both a liquid and a solid. When you push and squeeze the mixture, it behaves like a solid, but when the mixture relaxes it behaves like a liquid. You can keep it solid by squeezing in your hand, but it flows out as soon as you relax. This change happens very quickly - as the egg hits the ground, the mixture solidifies around the egg
* Safety:large amounts shouldn't be disposed of down the sink, try to avoid getting on clothes, tell Beavers not to throw / splash at each other, e.g. in eyes
* Demonstration: https://www.youtube.com/watch?v=idCFb3DqWkk
* Instructions for resetting experiment: put the mixtures in a sandwich bag and put in the bin; use clean bowls / plates; ask a parent to rinse the dirty ones after session 1 so they're ready for session 3;