# Exercise 2. Calculate variation of internal energy

Calculate $\Delta U$ for a system undergoing an endotermic process in which 15.6 kJ of heat flows and where 1.4 kJ of work is done on the system.

Solution:

$$\Delta U=q+w$$

where $q=15.6\;kJ$ and $w=1.4\;kJ$

$$\Delta U=15.6+1.4=17.0\;kJ$$

The system increases its energy in 17 kJ.