Visit to Jawahar Navodaya Vidyalaya, Rangareddy district Grades 7, 8 visit
Monday, Nov 10, 2014
Table 1: Nucleation vs Acid/Base reactions: (Mamta, Nirupama)
1. Test pH of diet coke and milk separately
2. Add (i) mentos (ii) baking soda (sodium bicarbonate) to 2 separate 2-litre bottles
of (diet) coke. Measure pH of each mixture afterwards. Different reactions in the
two cases: fountain for (i), volcano for (ii). pH does not change for (i), changes for
(ii). CO2 adsorbs on mentos surface, making it buoyant.
3. Club soda + chocolate. Layer of CO2 adsorbs on chocolate, makes it buoyant. When
it reaches surface, bubbles burst, it sinks again. Process repeats.
Materials needed:
Coke/diet coke bottles: 8, Peppermint mentos packets: 8, Baking soda packets: 4, Milk
chocolate: 4, Plain soda: 2 bottles, pH paper
Table 2: Solids, Fluids, surface tension, soap, and soft matter (Rashmi, Pankaj)
1. Illustration of surface tension: Razor blade floating on water.
2. Water + pepper + drop of dish-washing liquid. Soap molecules have hydrophilic
heads and hydrophobic tails, so heads line up at air-H2O interface, push out pepper.
What does soap reduce? Surface tension.
3. Fill cup with water, place cardboard on top, turn glass over.
4. Milk + food colouring + qtip soaked in dish-washing liquid. Swirl patterns form as
soap goes to water – milk fat interfaces.
5. Shaving cream: mixture of liquid and gas, behaves like solid/liquid depending on
strength of force applied. Squirt some into a cup, hold cup sideways, does not fall
under gravity. Squirt between paper/Al foil plates, show that it behaves elastically.
Materials needed: Razor blades: 2 packets; dish-washing liquid; liquid food colouring (2
colours); full cream milk (4 packets); 1 packet of qtips; pepper (1 packet); shaving foam (1
can); plates: Styrofoam or Al foil, need at least 20; cups, cardboard pieces, bucket to hold
liquid waste.
Table 3: Granular materials: solid or liquid? (Sumit, Parvathi, Karthik)
1. What is pressure? Magdeburg hemispheres, pressure mat on stool
2. Flow of water from holes at different heights in a bottle – show pressure
dependence of flow velocity.
3. Lit candle in H2O filled plate, cover with tube, candle goes out, H2O level goes up.
Candle heats air. When it goes out, temperature drops, resulting in pressure drop, so
water level rises.
4. Comparison of granular vs fluid flow under gravity. Two tall (1 litre) glass cylinders,
one filled with sand with 10 mm opening at base, one filled with water with 3 mm
opening. Allow both to begin draining simultaneously, mark level every 5 seconds.
Compare markings – sand should be equally spaced, water should have markings
with decreasing spacing – i.e. drainage speed stays constant for sand, decreases for
water. This is because pressure on wall of water container changes linearly as level
of water decreases, but since pressure on wall of sand container remains
approximately constant, the speed at which the sand drains does not change.
5. Cans in sand vs cans in H2O. Consider two cans, one open at one end, the other with
holes drilled in it. Compare how they behave when pressed downward into a bed of
sand with when they are pressed into water. In sand, the can without holes moves
more easily; in water, the reverse is true. This is because the air trapped in the can
fluidizes the nearby grains of sand as you push it down.
Materials needed: dry sand for basin, plastic basins - 2, 4 soda cans, with two open at both
ends; sieved sand for flow experiment, mug to hold it, water bottle for second tube, bucket
to hold draining water, tall clear bottle with small holes and cork plugs, marker pens (2),
candle, glass tube.
Table 4: Driven systems (Gangaprasath, Thejas)
1. Macroscopic model of Brownian motion: steel balls vibrated on speaker, with
aluminum foil ball executing random motion on top.
2. Corn starch mixed with water (2:1) ratio. Shear-thickening, non-Newtonian
liquid.
3. Cornstarch: Faraday waves + monsters. Need two setups. One with plastic dish,
the other with a soft plastic cover that can be molded to shape of speaker.
4. Macroscopic Model of 2D crystal formation: self-assembly, crystalline defects
Materials needed: plastic dish that will fit on speaker – (2); steel balls, aluminum foil ball,
plastic wrap – 1 packet, 2 kg cornflour/starch; plastic container for corn starch, water.
Table 5: LN2 related and other assorted demos (Shubha, Bharath)
1. Balloons in liquid nitrogen. As N2 inside balloon liquefies, can fit many balloons
into a small volume. Then throw them out and watch the balloons expand.
2. Dip flower in LN2, then shatter with a hammer
3. Optics: floating image, disappearing test-tube
4. Gravity: drop a 100 rupee note, paper + keys
5. Inertia demo: coins + cardboard pieces on top of cup.
Materials needed: balloons (small: 5 packets), LN2, flowers (10), hammer, Styrofoam
container for LN2 + balloons, LN2 safe gloves, cooking oil, test tubes, beaker, scrap
sheets of paper.
160 kids, 5 tables, need 10 repetitions of each demo.