A student investigates the temperature change during the endothermic reaction between citric acid and sodium hydrogencarbonate solution. The results of this experiment are shown in the table below.
| Measurement | Temperature in ∘C^\circ\text{C}∘C |
|---|---|
| Temperature of sodium hydrogencarbonate solution at start | 20.2 |
| Minimum temperature of mixture at end | 11.4 |
Calculate the change in temperature. You must include a sign and a unit in your answer.
