When fire is created. In which like methane and oxygen molecules in a burner they move around and when he give them a spark they gain energy and move faster and break apart. And hit each other and loose energy in friction and sound, but what is this saying that they create more energy than the energy required to start the reaction. I really don’t understand that
In: Chemistry
A spark can start a bonfire. The bonfire produces more energy than it took to create a spark.
More energy was created, than it took to start the reaction.
If you have a bowling ball at the top of a hill, and it only takes a slight nudge to get it rolling, the bowling ball will have a vastly higher amount of energy at its top speed than the energy it took to nudge it off the top of the hill.
Similarly, the spark was a relatively small amount of energy which causes ignition of large amount of potential energy stored in the rest of the methane/oxygen.
You have to pay $5 for the gas to drive to work. You work 8 hours and get paid $100.
There’s an initial fee that you get back afterwards. The initial fee is energy to break apart the molecules, but once they’re broken they’ll snap back together and release way more energy in the process.
In chemistry you get energy out of a system by going from a less stable state (higher energy state) to a more stable state (lower energy state).
Let’s say the it takes energy to break the methane and oxygen (CH4 and O2) into single atoms takes X energy. Forming the CO2 and H2O yields (gives out) 3X energy netting us 2X energy. Then the reaction is generating enough heat to start reactions between other molecules, that 3X energy could start 3 other reactions and will continue until all of the methane/oxygen are burned up. So we end up with 2X energy units out of this.
(In reality the math is a bit more complicated as the reaction is CH4+2O2=> CO2+2H2O and the bond energy for each molecule is different, but to find the energy you’d take the energy out from the products and subtract the energy input needed to break the bonds of the reactants)
First it’s important to realise that energy can’t be *created* or *destroyed*. It can only be transferred into various forms, and one of those forms is being in chemical bonds.
Breaking bonds requires you to input energy, to pull two things apart. Forming those bonds means the involved atoms/molecules reach a lower energy state, and that energy has to be released in some form. The amount of energy required/released depends on how strong the bonds are (and therefore how stable the molecule is).
So for burning methane, the chemical reaction is
CH4 + 2O2 –> CO2 + 2 H2O.
The energy required to break the C-H bonds in the methane and the O=O bonds in the oxygen, is less than the energy released when the C=O and O-H bonds form in the products. So it releases more energy than it took to react.
The spark provides the thermal energy to those first few methane and oxygen molecules to react and break the chemical bonds. That reaction releases heat, which causes more molecules to react, releasing more energy, and so on.
This is why you can’t really burn water. Those O-H bonds are pretty strong, and whatever you’re burning the water with would have to have even stronger bonds to form during burning for the reaction to progress.
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