In this video, I'm going to introduce a lot of conservation on one particular example, which is the law of conservation of energy. I'm going to start this video with a little demonstration, and I want you to come up with an equation for my demonstration. One and a half is a glass of water that this field would less than half a water. And I want to find you to find the equation that describes how much water is in the glass after a quarter of a bit more in. So this is the initial state. I have some water in my glass, and then I'm going to add more. And now I have the final amount of water in my glass. So please pause the video and think about how the initial amount of water in the glass relates to the final amount of water in the glass. Once you have written down your equation, come back to the city. So I think all of you have probably come up with something like this. And final amount of water is equal to the initial amount plus what I added. Now if I make say this is even more general, I could say what I have after is what I had before. Plus the change. Now in my example with the water, the change could be positive or negative. The change could be adding more water. So after I have more than half before, the change could be negative and taking out water. So what I have after is less than before, or I could just keep one glass and then the amount of water in the glass is conserved. I don't have any change. What I have after is what I have before. Now this is the basic of the laws of all laws of conservation. And there are many of them. You have conservation of matter, conservation of charge, conservation of spin, conservation of energy, conservation of momentum, the list of all and all and all and all. And once you understand this, one basic tip that what you have after is what you have before plus the change. And you will understand all of these conservation laws. Now in the case of energy, so for energy, conservation of energy, energy, energy. I can rewrite this as my energy final is my energy initial, just to change. Now the change where we talk about energy can come in two ways. It could come through mechanical work, some mechanical work. Or it could come through heat. Once again, if my work is positive, my final energy will be higher than the initial one. If the work is negative, the final energy will be lower than the initial one. Same time with the heat. If we are adding heat to the system, the final energy will be higher. If you are moving heat from the system, then the final energy will be lower. Now in your chemistry classes, you are mostly concerned about just looking at the heat. So you know this equation and deform it out to make any work. In your termed dynamics classes, you are actually looking at both of them at the same time. And now in your mechanics class, there are most interests about mechanical work and we are usually going to assume that heat is zero. Then there is even the simple case where we have conservation of energy where there is no external work entering or leaving the system, where final energy is equal initial energy. So one equation for your chemistry class, for your termed dynamics class, for your mechanics class, and for your simple mechanical situation for conservation of energy, always on the same principle. What you have after is what you have before plus the change.