in this video, we're taking a look at the first law of thermodynamics. Now, the first law of thermodynamics deals with energy, and it deals with the conservation off that energy. Eso basically energy cannot be created out of nothing. The same energy that exists now is the same energy to existed thousands of years ago. So that's the whole premise behind this first law of thermodynamics.
First Law of Thermodynamics
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So as we discussed before, the first law of thermodynamics deals with the conservation of energy. Now this energy that we're talking about can sometimes be transferred between two different ideas. Recall that our system represents the chemical reaction while the surroundings represent everything else Now in terms of systems were first going to say that there are three major types of systems in the first type. It involves the transferring of both matter and energy between systems and surroundings were going to say here, since you're able to transfer, both of them were going to say that this is an open system. The next one involves us not being able to transfer. Neither matter or energy between your system and the surroundings were going to say this is coined an isolated system, then finally, the last war most interested with Onley involves the transferring of energy. So this could be thermal energy, nuclear energy, solar energy, just energy itself between our system and surroundings. This is our closed system, and the first love dynamics is in reference to a closed system because we're talking about Onley, the conservation of energy. If my system gains 100 joules of energy because my surroundings have lost 100 joules of energy. Okay, so the total amount of energy is going between those two. It's never being lost on a journey from one to the other. Now again, remember, our system itself represents our chemical reaction. So this container here, which contains these gashes molecules reacting with one another, represents our system. Heat, which is symbolized by the variable que can either go into this chemical reaction or can exit this chemical reaction Since the gas molecules are is the chemical reaction in our system. Everything outside of that is coined our surroundings. You, me, everything else. Now, how is Q involved, Um, in terms of our chemical reaction. Well, remember here that Delta U, which is equivalent to Delta E, represents the internal energy off your chemical reaction the internal energy of your system. It is equal to Q plus W. We're going to say here that Q is representative of Heat. W is representative of work. We're gonna say that Q is equal to Delta H, which is our entropy. This is true when the pressure is constant and then work itself is equal to negative pressure. Times change in volume. So these air concepts that we should be familiar with based on previous videos now remember heat itself and work can either be positive or negative here. Q, which is heat will be positive of the system. Gains, absorbs or takes in heat or energy from the surroundings. Or it could be negative if it loses, evolves, gives off or releases heater energy to the surroundings. And that's what we're talking about with the first law of thermodynamics. Is the system gaining heat or energy from the surroundings? Is the system losing heat to the surroundings and then work? Work can also be accompanied with this whole idea, we're going to say here work can also be positive or negative. It's positive when work is done on system by the surroundings. Now, just imagine that in this container we have a piston that can either push down on my gashes mixture or my gaseous mixture itself can push back thio, increase the volume around it. So sometimes if we're removing heat from our system to the surroundings, we're gonna have a decrease in our volume, and the piston may slide down, compressing the gas mixture. So if work is being done on system by surroundings. We're gonna say work will be positive and the piston itself represents the surrounding that's pushing down on the gas is so your volume is compressed or if he is coming into the system, the gas molecules could absorb that thermal energy, move faster and basically push back on the piston, giving themselves more room to move. So in this case, work would be negative. Work would be done by system on surroundings and hear your volume would basically increase. Just realize here that when we're talking about the first law of thermodynamics, were basically just talking about, um, the system gaining or releasing energy, usually in the form of heat. And this absorbing or releasing if he can have an effect on how gas molecules, um, react with the container that they're in, otherwise increasing or decreasing our volume, which is connected toe work. So just remember, there are three different types of systems that exist, but it's this last system here which goes hand in hand with this whole idea of the first law of thermodynamics