A student investigates the temperature change of a neutralisation reaction between an acid and an alkali.
The student puts the alkali in a reaction vessel and adds the acid in 5 cm35\text{ cm}^35 cm3 portions from a burette, recording the temperature of the mixture after each addition.
Explain how using a polystyrene cup instead of a glass beaker improves the accuracy of the temperature measurements.
The results of the experiment are shown below:
Volume of acid added (cm3)Temperature (∘C)021.5524.01026.51529.02030.52529.03027.5\begin{array}{|c|c|} \hline \text{Volume of acid added (cm}^3\text{)} & \text{Temperature (}^\circ\text{C)} \\ \hline 0 & 21.5 \\ \hline 5 & 24.0 \\ \hline 10 & 26.5 \\ \hline 15 & 29.0 \\ \hline 20 & 30.5 \\ \hline 25 & 29.0 \\ \hline 30 & 27.5 \\ \hline \end{array}Volume of acid added (cm3)051015202530Temperature (∘C)21.524.026.529.030.529.027.5
(i) Describe the pattern in temperature change as the volume of acid increases from 0 cm30\text{ cm}^30 cm3 to 30 cm330\text{ cm}^330 cm3.
Explain how these results demonstrate that the reaction is exothermic.
State the meaning of the term activation energy by completing the sentence:
"Activation energy is the minimum..."