 These are potato chips, crisps in England. The chemicals in here are a concentrated source of energy that my body could store for later, or it could burn now to power me to do things that I think I need to do, like mow the lawn. And this is gasoline. The chemicals in here are a concentrated store of energy that I can use to power my lawn mower to help me mow the lawn. So, if I were to take my chips, dump them on the driveway, and stomp on them with my big boots, the chemicals, the energy would still be in there, but it just wouldn't be as useful to me, especially if I took my lawn mower and I spread them all over everything. So, the stuff is there, the energy is there, but I've made it no longer useful. In exactly the same way, there's now less gasoline in the mower than there used to be. I have burned it. The stuff has gone into water vapor and CO2 in the air, and the energy, a little bit of it, made noise to annoy the neighbors, but eventually that just heated up the surroundings, and a lot of it went right into heat, so if you touched the wrong piece on this mower, you would burn yourself now. So, what we see in the real world, normal times, stuff and energy are not lost or made, but they're changed from one type to another. And with energy, we tend to change it from useful types to things that are not as useful and eventually the heat that spreads out and does no good for us. A lot of the history of humanity has been finding concentrated sources of energy and trying to get useful things out of it as we change it into useless heat that spreads around the world. That may give you an idea that we'll come back to later. If we were using sun or wind or hydropower to run an electric mower, I'd be making a lot less noise. I'd be making a lot less heat. I'd be using the energy I bought for what I wanted rather than wasting it.