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fireworks...50 fire facts

Harnessing the technology of fire is one of our oldest human achievements, but just how much do you really know about the science of burning stuff?

Grab a spud and gather round the bonfire!

miscellaneous

Make a career out of it
If you are interested in chemistry and physics, art or music, you could be a pyrotechnician. There are no schools or universities you can go to, to learn about fireworks but there are people who organise shows who may be willing to talk to you and give you advice.

Waw, waw, waw (Fire engine noise)
Most fires at home start in the kitchen and chip pans are the main culprits.

Glowing in the rings
There are fab necklaces that glow when you give them a snap and a shake. The snap breaks a sealed glass vessel within the necklace. The vessel separates two chemicals, one inside the other outside. By snapping then shaking the necklace you mix the two chemicals together and a chemical reaction occurs. The reaction produces a lot of energy. The energy isn’t given off as heat but as light, it’s called chemiluminescence and in nature it happens in a firefly’s bottom.

It’s hot, dangerous and uncouth
Never throw water onto hot oil. It sinks under the oil and turns to steam because the oil is hotter than boiling water. The steam expands and spits out the oil on top of it.

It’s hot, hot, hot…
The hottest thing in the solar system is the centre of the Sun – it’s core can reach temperatures of 15 million Celsius.

Your name in lights
The bright light from a sparkler triggers nerve cells in the retina at the back of our eye. These nerves cells remain triggered for a short while after the sparkler has moved so we can see the path that the sparkler took. The same trick can be done with a camera – if the shutter is left open the light trace from the sparkler leaves messages on the film that you can only see on the developed image.


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fire - general

Strike a light
Starting a fire is like pulling a trigger - it just needs ignition energy for oxygen to react with the fuel.

Match heads need very little energy to ignite them – it takes a lot more friction to create enough heat to light the other end.

Ouch it’s hot
The reactions in fire break and make bonds - making new bonds gives out energy as heat.

Flames are burning gases released from the fuel as it heats up.

The heat of a fire excites electrons in the flames giving them energy that they release as light, which we call incandescence. It’s what makes a fire glow.

Fire makes fire
The heat of a fire starts more oxygen reactions with fuel to create more fire.

Flames contain hot gases that float upwards sucking in oxygen at the base of the fire to react with more fuel.

Flaming shapes
Flames get their shape from the hot gases as they rise.

Flames are round in space because there is no gravity. The flames don’t float they spread out evenly.

Flaming colours
Flame colour depends on what’s burning and the temperature it burns at. When you have lots of colours there are many different fuels burning at different temperatures.

Smokey Stuff
Smoke is tiny particles containing compounds of hydrogen, carbon and oxygen.

You can get sublime smoke without fire - when frozen carbon dioxide turns directly from a solid into gas it looks like smoke. It’s not smoke it is sublimation of dry ice.

Leftovers
Char is the black stuff – it’s mostly made of carbon and won’t burn easily.

Ash is the stuff that won’t burn – it’s minerals.

Soot is carbon particles – these are carried up in the hot gases produced by the fire.

Smouldering embers have no more combustible gas to release so don’t have any flames. They continue to react with oxygen and slowly burn away.

Burn baby burn – NO!
Some fire retardants reduce the flammable gases given off when an object is heated so the fire never really gets going.

Other fire retardants create a layer of char on the surface that doesn’t allow oxygen to react with the fuel beneath so the fire extinguishes itself.

Pure oxygen won’t burn because it can’t react with itself.

If there’s no fire there’s something missing.
There’s no fire without oxygen – it has to react with the fuel.
There’s no fire without fuel– it has to react with the oxygen.
There’s no fire without heat – it is needed for ignition to start the reaction.


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fireworks - general

Exploding bullets
Fireworks are giant sparklers fired into the sky like bullets.

The chemical mix
Just like a candle’s flame, a firework needs fuel and oxygen in order to burn, but instead of getting the oxygen it needs from the air it’s contained in chemicals called oxidisers that are packed into the firework.

Fast or slow?
Fireworks burn slowly like a candle or explosively like a stick of dynamite depending on how fast the oxygen is released.

Bang!
Explosives burn fast, releasing lots of hot gas, which blasts out destroying anything in its path.

Stars in the sky
Fireworks nearly always have added explosives sending out their sparkly packages or stars in an amazing variety of shapes.

Each star is like a giant sparkler - they contain fuel, an oxidant and chemicals giving the firework spectacular colours.


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fireworks - shape and colour

It’s the colour that counts…
Each colourful chemical in a firework is packed in as a salt.

Strontium or lithium salts give red light, barium green, yellow is a sodium salt and blue is made with copper salts.

All shapes and sizes
The salts come in ‘stars’ and the way they’re packed in the shell creates the shapes when the firework explodes. Packing the stars into the shell differently creates different shapes in the final firework explosion.

A ring of blue stars and a ring of red stars in the shell result in two perfect rings of colour in the sky.

Whistle while you work
Whistling fireworks force the carbon dioxide gas from the burning fuel out a hole in the shell.


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fireworks - movement

Slow and controlled
Controlled explosions produce shapes like palm trees or slithering snakes. Fast explosions would be a disappointing sight.

They’re out of control!
We can’t control the firework in the air! But with a radio controlled rocket we could write our name in the sky.

Firework Forces
Some fireworks are like space rockets - burning gases from the fuel shoot out the bottom zooming the rocket upwards.

Fireworks that send out bright stars snaking around in the sky are like tiny rockets. The burning fuel sends them spinning in all directions.

A Catherine Wheel is a trapped rocket. Unable to go up it spins round and round spitting out fire and sparks.


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fireworks - safety

Fireworks falling from the sky
Most fireworks burn up in the sky, but sometimes small, light bits of ash, paper or cardboard make it back to the ground.

A firework that returns to the ground without exploding can be very dangerous. If this happens DON’T TOUCH!

Safety at home
It is always safest to go to a public firework display but if you are going to have some fireworks at home remember to take care.

Keep sparklers away from small children, wear gloves and don’t light more than one at a time.

Follow the instructions on your fireworks, keep them in a closed box until you are ready to use them and definitely don’t put them in your pocket.

Most accidents happen when people go back to a lit firework, stay away from lit fireworks, even if you think the fuse has gone out.

Keep your pets indoors - fireworks can be frightening as well as dangerous to animals.


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fireworks – sparklers

Candles with an added oomph!
Sparklers burn slowly like candles, but where candles have wax and a wick, sparklers have powdered carbon and sulphur stuck together on a wire with sugary glue.

Glittering flakes
Sparkler’s sparks come from flakes of metal. Aluminium, iron, steel, zinc or magnesium can be used to create the jagged sparks.

As the metal on a sparkler heats up the flakes shine like a hot poker in a fire, sometimes the metal can even burn.


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candles

Breaking bonds
Burning a candle makes and breaks bonds of the wax molecules – making a bond gives out more energy than is used in breaking one so the candle keeps alight.

Grimy candles
Wax is made of molecules of hydrogen and carbon that burn in air to release carbon dioxide, water, carbon monoxide and carbon (soot).

Drip, drip, drip…
For a dripless candle add stearic acid to the wax, it’ll make it hard and more difficult to melt.

Wick-ed candles
The wick of a candle is always playing catch-up because it burns slower than the wax.

The hottest part of a candle flame is the blue bit, its 1400&Mac176;C, the orange looks warmer but it’s only 800&Mac176;C.

Environmental damage
Candles burn carbon to release the greenhouse gas carbon dioxide.

The oil that makes paraffin wax formed millions of years ago, by burning these candles we release this stored carbon and increase carbon dioxide in the air.

Beeswax is made by bees. The carbon in these candles hasn’t been stored long so burning them won’t create additional greenhouse gases!


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burns

Spontaneous Human Combustion
Too much stress has been suggested as the cause of spontaneous human combustion where someone burns to ashes with seemingly no source for the fire. It is more likely that a combination of smoking, drinking and then falling asleep is the cause with the poor victim slowly burning away like a candle!

When it all goes wrong
Fireworks can cause burns.

First-degree burns are painful but they aren’t serious, with second-degree burns there are blisters and lots of pain, but with third-degree burns, by far the worst, there may be no pain because the nerve endings to the skin have been destroyed.

A skin graft can be used to protect the burn. Doctors can take a permanent one from another part of the body. They can take a temporary one from another person or even a pig, but the body rejects this in a few weeks.

The body can repair minor burns without much help, but its best to immerse a burn in cool water immediately and keep it very clean.


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flame throwers

Flamethrowers launch burning fuel into the air.
They’ve been used in battles since ancient Greek times. The Byzantine forces pumped highly flammable liquid through narrow brass tubes creating a jet of fire to attack the enemy. The fire probably travelled a metre or so - modern military flamethrowers have a range of over 150 meters - that’s one and a half football pitches!

Take one steel tube fill with a source combustible gas and oxygen that comes out at high pressure, submerge underwater, pass an electric current across the mixture as you eject it. This ignites it and you’ve got yourself an underwater flamethrower, or welder.

Fire breathers are human flamethrowers. They take a swig fuel like kerosine into their mouths and spit it out across a lit flame. Do not do this it is unbelievably dangerous - they are highly skilled and probably have very unpleasant breath.


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forest fires

Forest fires can start naturally.

Some fires are accidents - a single spark from a train wheel can start a fire.

Sadly arsonists, who perversely get a kick out of burning stuff, start a lot of forest fires.

In the year 2000, 92 million hectares of the world’s forest burnt.

Out of control fires can run up hills as fast as 24 kilometres per hour.

Fire in the tree-tops can leap from tree to tree at 160 kilometres per hour.

Many plants seeds rely on the heat of a fire to germinate.

Some plants’ leaves contain flammable stuff that actively encourages fire. A chemical in the ash initiates germination and the plants quickly take advantage of the available space.

Insects burn just like every other creature that can’t move fast enough to escape – they probably pop as the gas inside them expands making them explode.

Birds returning after fire use it as and opportunity to feast on charred insect.


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sparks and lightning

Sparks coming off a fire are burning bits of fuel thrown into the air.

Sparks from a lighter with no fuel left are tiny bits of burning metal – friction has given these cast off fragments enough heat to react with oxygen in the air.

Burning sparks wouldn’t appear in a vacuum because there’d be no oxygen to react with.

You can get sparks in a vacuum without oxygen by incandescence. This is when charged particles like electrons can give out light when they move around.

Light bulbs are mini vacuums. There’s no burning because there’s no oxygen, they glow because of incandescence – as they heat up charges move and give out light energy.

Sparks that you see when you take a synthetic jumper off are static charges. They glow because of the jumping charge. It’s incandescence – the giving off of light energy.

Static sparks are like tiny bolts of lightning.
With lightning it happens on a grand scale, lighting up the sky as the multitudes of ions jump through the air.


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