Question

The air in an inflated balloon (defined as the system) is warmed over a toaster and absorbs 120 J of heat. As it expands, it does 78 kJ of work.

What is the change in internal energy for the system?

Answer 1

Answer : The value of
`\Delta E` for the system is -77880 J

Explanation :

First law of thermodynamic : It states that the energy can not be created or destroyed, it can only change or transfer from one state to another state.

As per first law of thermodynamic,

`\Delta E=q+w`

where,

`\Delta E` = internal energy of the system

q = heat absorbed by the system

w = work done by the system

As we are given that:

q = 120 J

w = -78 kJ = -78000 J (1 kJ = 1000 J) (system work done by system)

Now put all the given values in the above expression, we get:

`\Delta E=120J+(-78000J)`

`\Delta E=-77880J`

Therefore, the value of
`\Delta E` for the system is -77880 J