[sodium.dioxid]

It seems redundant to rely on a chemical bond to provide you energy, since it demands that same amount of energy to break it in the first place. It's giving with one hand and taking with the other hand. How is this useful?

[Borek]

You (almost) never just break bonds. Usually you break one bonds and create a new ones, and it is the difference between energy of bonds produced and broken that counts.

Unless you are asking about something completely different, your questions are cryptic.

[fledarmus]

In a sense, you are right. Burning things doesn't generate energy, it releases energy that has been stored in chemical bonds. Consider fossil fuels: given plenty of oxygen and sufficient energy for activation, the carbon-carbon and carbon-hydrogen bonds in hydrocarbons all break down, and carbon-oxygen and hydrogen-oxygen bonds are formed, giving an overall process where the hydrocarbon reacts with oxygen to give carbon dioxide, water, and energy.

The energy was originally provided by the sun. Plants are factories which convert carbon dioxide, water, and energy derived from sunlight, into a wide variety of biological molecules and oxygen. These biological molecules are further modified by energy from geological processes after the plant has died. Millenia of pressure and temperature from those processes gradually convert the biomass into oil, coal, and gas.

All we are doing is digging up the products and burning them to release the energy that has been stored in them.

[sodium.dioxid]

your questions are cryptic.

No, CHEMISTRY is cryptic. It is filled with ambiguous responses to questions. For example, when bonds are made, we are told that it releases heat. To me, what is more important is knowing HOW that heat is released. But no, the lazy answer is to just say "heat is released". Is this heat a ghost?

Let's assume that ONLY two molecules (isolated in a black void deep in space) react to form a bond (and let's assume that this is a non-light-producing reaction). In this case, what would you say heat is? It just doesn't make sense for bond formation to release this thing called 'heat'.

the difference between energy of bonds produced and broken that counts.

This is ambiguous. How do you explain this to a 10 year old? I am hoping to hear more if you can elaborate. I made a different post to get help on decrypting the meaning of "bond energy".

[Borek]

No, CHEMISTRY is cryptic. It is filled with ambiguous responses to questions. For example, when bonds are made, we are told that it releases heat. To me, what is more important is knowing HOW that heat is released. But no, the lazy answer is to just say "heat is released". Is this heat a ghost?

No, heat is a form of energy. When you mix reactants you observe that the temperature of the reaction mixture goes up - that means heat was released. This is purely phenomenological observation. Yes, there are mechanisms behind. The most obvious one is that reaction products have larger kinetic energies after the reaction that they had before. The other one is that energy is emitted as electromagnetic radiation. These mechanisms require quantum mechanics for the detailed description.

Let's assume that ONLY two molecules (isolated in a black void deep in space) react to form a bond (and let's assume that this is a non-light-producing reaction). In this case, what would you say heat is? It just doesn't make sense for bond formation to release this thing called 'heat'.

Yes it makes sense if you know how the temperature is related to the average energy of molecules. The kinetic energy of molecules produced will be larger after the reaction than the kinetic energy of the molecules before the reaction. This means their temperature is higher, which is equivalent to stating they were heated. This is basic physics.

[sodium.dioxid]

The most obvious one is that reaction products have larger kinetic energies after the reaction that they had before. The other one is that energy is emitted as electromagnetic radiation. These mechanisms require quantum mechanics for the detailed description.

THANK YOU SO MUCH! This is the kind of thing I was looking to hear. Awesome explanation. Key phrases were "quantum mechanics" and electromagnetic radiation".

Yes it makes sense if you know how the temperature is related to the average energy of molecules. The kinetic energy of molecules produced will be larger after the reaction than the kinetic energy of the molecules before the reaction. This means their temperature is higher, which is equivalent to stating they were heated. This is basic physics.

So, released energy = kinetic energy + electromagnetic radiation?

But I have a question about kinetic energy. If two molecules are heading at each other with the same speed in opposite directions then they lose kinetic energy after bond formation, correct?

[Borek]

But I have a question about kinetic energy. If two molecules are heading at each other with the same speed in opposite directions then they lose kinetic energy after bond formation, correct?

Yes, it is in a way similar to perfectly inelastic collision.