And the increase in temperature will transfer energy from this section to the surroundings, to the water. And you could measure the change in temperature using this thermometer. So the initial and final temperature, just like you would in a coffee cup kilometer. So finally, you can use the change in temperature and the formula to calculate our energy change. Now let's look at our first law of thermodynamics which states that change in energy is equal to heat plus work. Now, in this case, no mechanical work is done and no PV work is done because change in volume is zero.