Number 20: Black Worms

Firework season (in the UK) is approaching so I thought it would be fun to find a simple homemade pyrotechnic. And here it is, 'black worms' made with stuff you're bound to have around the house.

You'll need:

• Icing or powdered sugar (if you haven't got any already then just wizz some granulated sugar in a food processor).
• Bicarbonate of soda
• A pot of sand
• An alcohol based handwash gel
• A pot and a teaspoon
• Matches or a lighter

Safety: 

We're using flames and flammable materials so this is best done outside and with adult supervision.

What to do:

1. Mix 2 teaspoons of icing sugar with 1/2 teaspoon of bicarbonate of soda.

2. Make a small depression in the sand and then spoon the sugar/bicarb mix into it.

3. Squirt the handwash gel all the way around the pile of the sugary mix.

4. Light the gel and watch the snakes grow!

What's going on?

The handwash gel contains ethanol which burns pretty well. This heats up the bicarbonate of soda, which gets converted to carbon dioxide, sodium carbonate and water. Meanwhile some of the sugar starts to burn i.e. it reacts with the oxygen in the air, and ends up as more carbon dioxide and water plus  a whole load of stuff that comes form sugar that didn't burn completely. This is what causes the carmel smell and black sooty stuff.  Then all that carbon dioxide forms bubbles in the caramelised sugar and sodium carbonate which causes it to rise up as those little worm like towers.

Number 10: Polishing the silver

There's all sort of potions and polishes that you can buy to clean up the silver. Don't buy any of them. Because you can find everything you need to get the best cutlery sparking again in your kitchen cupboards.

What you'll need:

• Bicarbonate of soda
• Aluminium foil 
• A cup or glass
• Some tarnished silver spoon (its best if its solid silver, it will work with silver plated stuff, but you run the risk of removing the plating)

What to do:

1. Put a heaped teaspoon of bicarb into the glass.

2. Tear up 10 to 20 bits of foil and add them to the glass.

3. Put the spoon in the cup

4. Pour on hot water. Water from the hot tap will do fine. 

5.Stir and leave for 5 minutes.

6.Take the spoon out and inspect it. All the tarnish will have disappeared. 

Before

After

What's going on:

There's some pretty niffy chemistry going on here.  First lets dispel a little myth, the tarnish is not due to a reaction with silver and oxygen like a lot of people claim. Iron reacts with oxygen to make rust, but silver tarnish is something different. Silver tarnishes when it reacts with sulfur containing chemicals (usually hydrogen sulfide, which smells like rotten eggs) to produce silver sulfide. Eggs are particularly high in sulfur which is why they make your silver tarnish so quickly.

That's the easy bit. How the aluminium and bicarb work to clean the silver is a little more complicated.

Lets take a look at the chemicals that we start off with. You've got silver sulfide (the tarnish), sodium bicarbonate (the bicarbonate of soda), aluminium  hydroxide (the foil is actually covering in a layer of this, the aluminium itself is underneath and we need to get at it).

Step 1: The bicarbonate reacts with the aluminium hydroxide and turns is back to aluminium.

Step 2: The aluminium reacts with the silver sulfide to make silver and aluminium sulfide.

and that leaves you with nice clean silver.

Number 1: The Film Canister Rocket!

We're going to start with one of my favourites; the great film canister rocket!

You'll need:

• 1 film canister (you can still get them, try Jessops or anywhere else where they still develop film). The ones white ones with the white lids work best.
• Lemon juice or vinegar (lemon juice smells nicer, but vinegar works just as well)
• Bicarbonate of Soda 
• A teaspoon
• Some toilet roll
• SAFETY SPECS!

Safety:

Wear those safety specs and this one is best done with adult supervision. 

What to do.
1) Take everything you need outside
2) Put the safety specs on and keep them on until the end.
3 Take the canister and pour in the lemon juice or vinegar until you have about 1cm worth in the bottom.

4) Take a square of toilet tissue and put it on top of the canister, gently push the tissue into the canister so that you have a small pocket in the top. Make sure the tissue doesn't touch the liquid in the bottom.

5) Next spoon in 1 teaspoons worth of bicarbonate of soda. Then snap the lid tightly back on the canister. 

6) Now you have to be quick! Grasp the canister (keep it at arms length).  Turn the canister over and give it one or two good shakes. Put it, lid down, on a surface. 

7) Stand back and watch it fly!

Whats going on?

The bicarbonate of soda reacts with the acid in the vinegar or lemon juice to produce carbon dioxide gas (and water). As more gas is made the pressure inside the canister builds up, eventually the pressure gets too much and the lid pops off. The gas escapes out and pushes the canister up. 

This is exactly the way that real rockets work (except you can't get to the moon with bicarb and vinegar as a fuel). But your rocket does follow something called 'Newton's third law of motion', which states that "every action has an equal an opposite reaction". In this case this means that the action of the gas escaping from the canister has an opposite reaction which pushes the canister into the air.