First Law of Thermodynamics

by Jules Bruno
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now remember, heat is the flow of energy more specifically, thermal energy between a hotter object towards a colder object. So when heat applications, it transfers, um, heat from a hotter object to a colder object. Let's assume that the spirit on the on the left is at a higher temperature, and then the square on the on the right is at a lower temperature. Heat naturally moves from a place that is hotter toe a place that is colder Now the system on the left. It's losing heat. This one here is gaining heat Well, if you are losing so if it loses, evolves, release or gives off heat in the sign of Q would be negative. On the other side, the heat is going towards the cock, the colder object. So it is gaining heat. So if a system gains, absorbs or takes in heat, then it has a positive que so that's the way we observe the signs of Q. If heat is being moved, whoever is gaining the heat is positive. Que whoever is losing the heat is negative. Que Now work is a little bit different. Work is the fourth done by reacting molecules on a frictionless piston. All right, so we're going to say Here, let's say we have our gas molecules in this container and the piston here can move up or down. Let's say the gas molecules themselves wannabe spread out even more from each other, and they decide to push up against the pistons. So they're doing work on the piston here as a result of doing work on the piston. Here, there are going to have a negative W. If the system does work on the surroundings, it is a negative. W The surroundings here would be the piston or the container. Conversely, let's say the gas molecules are just hanging around, not doing anything, and some outside force decides to push down on this piston. The piston again is our surroundings. It's going toe come down, and it's going to squeeze down on the gas molecules. In this case, the surroundings are doing work on the system. If the surroundings air doing work on the system and the system is doing nothing, then work will be positive. That's because the system is not working against an opposing force. It's just sitting back and letting it happen, So just remember Q and W could be positive or negative, depending on situations. So just remember of our system gains heat. It's positive. Q. If it loses heat, it's negative. Q. If the system does any type of work, it's going to be a negative W and if the surroundings do work on the system, then it's positive W.