required practical: temperature changes

• Reactions can be exothermic or endothermic.
• In this experiment, the temperature change in an exothermic reaction, the neutralization reaction between hydrochloric acid and the alkali sodium hydroxide, is investigated.
• The independent variable in this experiment is the volume of sodium hydroxide solution, and the dependent variable is the maximum temperature reached.
• The control variables in this experiment are the volume of hydrochloric acid and the concentrations of both the hydrochloric acid and the sodium hydroxide solution.
• To measure the temperature of the acid, a thermometer is used and the temperature is recorded in a table.
• The maximum temperature reached is recorded when the reading on the thermometer stops changing.
• The experiment is repeated several times, increasing the volume of sodium hydroxide solution by 5 centimeters cubed until a maximum of 40 centimeters cubed of sodium hydroxide solution is reached.
• The results of the experiment are used to calculate a mean value for the maximum temperature reached for each volume of sodium hydroxide solution.
• A graph of the results is plotted to show that as the volume of sodium hydroxide solution increases, the maximum temperature reached also increases.
• At a certain volume of sodium hydroxide solution, the maximum temperature reached starts to decrease because there is not enough hydrochloric acid for all the sodium hydroxide to react.
• The maximum temperature reached decreases when large volumes of sodium hydroxide solution are added because the energy released by the reaction is spread out into a greater volume.
• A polystyrene cup with a lid is used in this experiment to measure the temperature because it reduces heat loss through the sides and the bottom and the lid, which is heat loss to the air.