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### Heat and systems

Posted: Sun Jan 21, 2018 11:44 pm
How can you tell whether or not heat is being transferred to the system or from the system?

### Re: Heat and systems

Posted: Sun Jan 21, 2018 11:47 pm
Heat transfers from a higher point of temperature to a lower one. So look at a problem and determine if the system losing heat or gaining heat.

### Re: Heat and systems

Posted: Sun Jan 21, 2018 11:48 pm
if you have deltaH/Q, you can look at the sign it has
-deltaH means that energy is released by the system (exothermic; the system is losing energy, thus the minus sign) and so energy is being transfered from the system to the surroundings. eg combustion reactions
+deltaH means that energy is gained by the system (endothermic) and so energy is being transfered to the system from the surroundings. eg the melting of ice

### Re: Heat and systems

Posted: Sun Jan 21, 2018 11:49 pm
When heat is transferred out of a system, heat is lost so the q value is negative (exothermic). When heat is transferred into a system, heat is gained so the q will be positive (endothermic). I hope this answers your question.