I’ve seen videos of people throwing firecrackers and dynamite and things like that into water and they still explode, but how do the fuses stay lit?
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The fuse doesn’t draw oxygen from the atmosphere to burn. Instead it contains an oxidiser. So it can burn under water.
Safety fuses, invented in the early 1800s, consist of a core of gunpowder wrapped in some sort of waterproof material, originally something called jute rope, but later replaced with other more reliable materials. Gunpowder contains it’s own oxidizer, so it will burn underwater so long as it stays dry.
There are a few kinds of fuse, it’s not fair to say *all* fuses are good underwater.
But the gist is that burning requires 2 ingredients, a fuel and something called an “oxidizer”, which is usually just oxygen gas from the air itself. So something like a piece of wood, the wood is the fuel and the oxygen from air is the oxidizer. Put wood in the water and it goes out because you removed the oxygen gas.
Certain materials, like gunpowder contain both the fuel and the oxidizer in one, they just need heat to start burning. You can fire a bullet underwater or in outer space, no air required.
So if you make a fuse literally out of gunpowder (yes, they do have these) it can burn underwater if you make it right (there are other problems with burning underwater like cooling the flame).
Fire requires three things to burn, often called the *fire triangle*. You’ll often hear this phrased as “air, fuel, and heat”. Remove any one of the three, and the fire goes out.
The thing is, “air” is a bit of an oversimpilification. What fire really needs is an *oxidizer*: something to fuel the chemical process called *oxidation* characteristic of burning. As the name implies, most of the time the oxidizer is oxygen, and most of the time that comes from the air.
But the oxygen doesn’t *have to* come from the air. As long as a suitable oxidizer is available (and there’s enough fuel and heat to start or sustain the reaction), other substances can be used. Most common fuses actually infuse the cord with an oxidizer to make it more reliable: the fuse burns in a controlled way and at a predictable rate, and outside factors like moisture won’t affect it. This is considered an important safety feature: you can control how long the fuse will burn by measuring out a specific length, and it’s very hard to make it burn any faster or slower.
The fuse needs oxygen to burn. If you make the fuse with some ingredient that can provide that oxygen (like rust, which is iron and oxygen), you can make a fuse that doesn’t need to rely on oxygen from the surrounding air to burn, and it can burn underwater.
You also want to make sure that the thing that contains the explosive is waterproof too, such as a plastic tube or paper dipped in wax, so that the explosive material will explode. Water-logged dynamite does not go boom, for example.
For something to burn you need 2 things: fuel and an oxidizer. The 2nd one is called an oxidizer because it donates oxygen to the reaction. Straight O2 is the most common one used, but it doesn’t have to be exclusively O2. There are several other molecules that are really good oxidizers such as NO3, ClO3, and ClO4. Some oxidizers are solids. Water is NOT an oxidizer, it’s too stable to let go of its oxygen that easily.
The reason why water normally puts out a fire is that the fire is using atmospheric O2 as the oxidizer and the water stops the O2 from getting to the fuel so the reaction doesn’t get the oxidizer needed to continue burning.
In the case of fuses, they’re usually a combination of gunpowder, a solid oxidizer, and a flexible, waterproof casing. The waterproofing prevents water from washing anything away and the oxidizer is mixed with the gunpowder so it will always have access to the oxidizer.
Most fuse material are hydrophobic and the material burning has its own oxidiser, therefore can burn underwater.
as a nieve person my answer would be:
things burn (combust) only because of three things
1) heat sufficent to start
2) fuel
3) presence of oxygen
remove one and it goes out
water will displace the o2 so then the fuse must provide its own o2 by some means.
FYI, a cheap black cat firecracker fuse is just paper and gun powder. If you throw those in water, the paper and gun powder will soak up water and it will not stay lit. An M80 has a waterproof fuse.
This is also why old, cheap fireworks don’t light, especially if you live in a humid climate, fuses absorb moisture from the air and won’t burn unless they are waterproof.
Water doesn’t just magically put out fire.
Fire needs oxygen, and smothering it in water deprives it if that.
Things need to be hot to catch fire, and water heats up slowly so it’s hard to make something wet hot enough to burn.
The fuse is made of a material that contains it’s own oxygen and burns hot enough that ambient water can’t cool it enough to put it out.
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