A system is a selected region with a selected boundary.$^1$ $E$ is energy
Energy change is calculated is: $\Delta E = E_f-E_i$
Endothermic change is a physical or chemical change where the energy content of the system increases due to an absorption of energy.$^1$
An example of an Endothermic chemical change is:$^1$
$$ 6\text{CO}_2\text{6H}_2\text{O} \overset{sunlight}{\longrightarrow} \text{C}6\text{H}{12}\text{O}_6 \text{ + 6O}_2 $$
If $\Delta E >0$ then that means that the change in the system was Endothermic.$^1$
Where the x axis is time and the y axis is energy.$^1$
Exothermic change is a physical or chemical change where the energy content of the system decreases.$^1$ An example is of an Exothermic physical change is the condensation of water.$^1$
If $\Delta E<0$ then that means that the change was Exothermic.$^1$
Where the x axis is time and the y axis is energy.$^1$