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Delta u, delta H, familiar state functions, q w changes in their values, q, w, heat and work.
U，△H，很熟悉的态函数，它们的值在变化；
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Delta v is positive in this direction here, the work is negative. So work on the system is positive. Work done by the system is negative.
功是负的，总而言之,外界对系统做功的符号为正。
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So if delta v is negative, in this case delta v is negative, OK, delta v is negative, pressure is a positive number, negative times negative is positive, work is greater than zero.
也就是当活塞,压缩气体的时候，做的功是正的，按照这一规定,我们需要在这里，加上一个负号，这是习惯规定。
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So delta u is just equal to the work but we also know what happens T2 because the temperature is changing from T1 to T2.
所以Δu等于输出的功,但我们也知道它会发生,同时我们知道温度从T1变到。
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q Work is zero. Delta u is w plus q, work plus heat. This is zero, this isn't.
功是零，△U是w加，功加上热量，这个是零。
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It makes sense, right, because you know we got less work out and delta u is the same right, so it must be that less heat got transferred.
这是显而易见的，因为输出的功更少,且Δu相等，所以需要的热量更少。
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U And then if we can also determine delta u, then we know this, we know delta u is q plus w w, then we can determine work as well, right?
然后，如果我们也能定出△,然后我们知道这个,我们知道△U等于q加？
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V Minus p2, V2. Minus p delta V. So the total work is the work from the left hand side plus the work on the right hand side, p1 V1- p2 V2 which is p1 V1 minus p2 V2.
负p2V2【w=-p2v2】，即负pΔ,所以全部的功就是,左边的功加上右边的功，等于。
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