Snap, crackle and snot

This session should take two hours and 15 minutes. 

This half day session is designed as an enrichment activity for 11–12 year-old learners. The event can be run at any time of the year, but a good time is in November, often as part of Chemistry Week, providing the opportunity for 11–12 year-olds to carry on their enthusiasm for science from primary school. The event consists of three 20 minute workshops with five minutes to change over, and finishes with a demonstration lecture for everyone.

Snap

Equipment

• Small vial with lid containing sodium silicate solution in a 1:4 ratio of silicate:water
• Three small pots of coloured crystals – eg any three from copper sulfate, nickel nitrate, nickel sulfate, cobalt chloride, cobalt nitrate
• Three pairs of tweezers
• Portion of ‘magic sand’ in a cup or beaker
• A second cup or beaker half filled with water
• Two demonstration beakers, one containing ‘self siphoning liquid’

Procedure

Crystal gardens

1. This should be done in groups of two or three
2. Using one pair of tweezers per pot, add a couple of grains of each colour crystal to the pot of silicone solution.
3. Place the lid on the pot and leave until the end of the workshop to view the growing crystal garden.

Magic sand

1. In small groups, pour the magic sand into the cup of water. Watch what happens.
2. Carefully pour the water back into the other cup.
3. Why is the sand free flowing and not wet?

Self siphoning liquid

1. Do this as a demonstration.
2. Start with the gel liquid in one large beaker.
3. Pour carefully from a height into a second large beaker while trying to adjust the pouring speed and the angle of the beaker so liquid gives the appearance of defying gravity and climbing back up.

Crackle

Equipment

• Table-top insulated container for liquid nitrogen
• Fruit or vegetables with a high water content
• Disposable rubber tubing
• Small hammer
• Heatproof mats
• Balloons
• Glow sticks
• Beaker of hot/warm water
• Flowers with big petals/heads

Procedure

Solids 

1. Take a length of rubber tubing and stick one end into the liquid nitrogen.
2. After a minute or so, remove it and show what happens to either end of the tubing when hit with a hammer (carefully)

Liquids

1. Immerse the heads of large flowers in the liquid nitrogen for approximately 30 seconds.
2. Ask for a volunteer (wearing safety glasses) and very gently smash the flower over their heads.

Gases

1. Blow up a couple of balloons and ask the audience what they think happens if you put the balloon in the liquid nitrogen.
2. Push the balloon into the liquid nitrogen and lift it out again when it has completely shrunk.

Reaction rate

1. Crack a couple of glow sticks to activate them. Discuss what is happening to produce the light in the glow stick. 
2. Place one glow stick in the beaker of hot water and the other in the liquid nitrogen.
3. After a minute or so, remove the glow sticks and compare them.

Snot

Equipment

• Polystyrene cup
• Wooden lolly stick
• Labelled food bag
• Borax solution (4% solution of sodium borate in water)
• PVA solution (4% solution of PVA solid in water)
• Food colouring
• A pipette per table

Procedure

1. Pour the PVA into a polystyrene cup to a depth of approximately 3 cm.
2. Add three drops of green food colouring to make a good snot colour. NB– too much food colouring affects the consistency of the slime.
3. Stir with the lolly stick.
4. Add a small amount of borax solution to the mixture.
5. Stir in the Borax and add a little more if necessary to get a good snotty consistency. Too much Borax will make the mixture too runny.
6. When a good consistency is reached, the mixture can be transferred to the bags either by pouring it or by hand if the students want to get a bit messier.

Health, safety and technical notes

Read our standard health and safety guidance here.

Wear eye protection.

Wear gloves.

Wear an apron.