EasyChemistryHigh School (11–12)Chemical Thermodynamics › Systems, Work, Heat and the First LawConceptualBoard Exam
Classify each as an open, a closed or a nearly isolated system, and give a reason: (a) a pressure…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Classify each as an open, a closed or a nearly isolated system, and give a reason: (a) a pressure cooker on a stove with its lid locked and its valve shut; (b) a cup of tea with no lid; (c) hot soup in a sealed vacuum flask; (d) a person running in a park.
Need a reminder? The key ideaShow
Open system: energy and matter cross the boundary. Closed: only energy crosses. Isolated: neither crosses. A state function depends only on the state of the system (p, V, T, U). Heat and work are path functions. Extensive properties depend on the amount of matter; intensive ones do not.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. The pressure cooker. Heat comes in from the stove, but no steam escapes while the valve is shut. It is closed.
Step 2. The cup of tea. Heat leaves, and water vapour escapes from the surface. It is open.
Step 3. The vacuum flask. Its walls keep heat in and its lid keeps matter in. It is nearly isolated.
Step 4. The runner. A person breathes air in and out, sweats, and gives out heat. It is open.
Answer: closed, open, nearly isolated, open.
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