Chemistry - Water becomes cold on mixing energy drink

Solution 1:

Well, the solution enthalpy of sugars is positive. I found these numbers on the internet

• $\ce{C12H22O11}$ (sugar(sucrose)) : 5.4 kJ/mol
• $\ce{C6H12O6}$ (glucose) : 11 kJ/mol
• $\ce{C6H12O6·H2O}$ (glucose monohydrate) : 19 kJ/mol

So if your "energy drink" is a dry powder (and not a readymade drink in an aluminum can), this could explain your observation.

You should however put a thermometer into your experiment, and get us some numbers. As is, my above is just another piece of guesswork.

Solution 2:

From the calculations (and from the enthalpy data posted by Karl, reference here), the following can be calculated:

1. Enthalpy of solution of glucose in the mixture, given by $$\Delta H_\text{glucose} = \frac{52}{100} \times 14.85 \times \frac 1 {180} \times 11000 = \pu{471.9 J}$$
2. Enthalpy of solution of sucrose in the mixture, given by $$\Delta H_\text{sucrose} = \frac{45}{100} \times 14.85 \times \frac 1 {342} \times 5400 = \pu{105.51 J}$$

By calorimetry, we have $$Q = mc\Delta T = 200 \times 4.2 \times 0.7 = \pu{588 J}$$

Adding the enthalpies of solution should give us a value close to the heat provided by water, and indeed it does! $$\Delta H_\text{glucose} + \Delta H_\text{sucrose} = \begin{array}{|c|} \hline \pu{577 J} \approx \pu{588 J}\\ \hline \end{array} $$