energy changes - required prac

the volume of sodium hydroxide solution

the maximum temperature reached

• volume of hydrochloric acid • concentration of hydrochloric acid • concentration of sodium hydroxide

• start by using a measuring cylinder to measure 30cm3 of dilute hydrochloric acid • Then transfer the acid to a polystyrene cup • Then, stand the polystyrene cup inside a beaker • Next, use a thermometer to measure the temperature of the acid, and record it in a table • then, use a measuring cylinder to measure 5cm of sodium hydroxide solution, then transfer it to a polystyrene cup • Place a plastic lid on the cup, and place a thermometer through a hole in the lid (the bulb of the thermometer must be in the solution) • use the thermometer to gently stir the solution • The temperature of the solution will increase as the reaction is exo, so record the highest temperature reached • Rinse out and dry the polystyrene cup • Carry out the experiment again, increasing the volume of sodium hydroxide solution until you get to 40cm3 • Repeat the whole experiment again, find a mean and draw a graph

to stop if from falling over

• the maximum temperature reached increases why? - because when we add more particles of sodium hydroxide, they react with hydrochloric acid, and since this is an exothermic reaction, more energy is released, therefore the maximum temp increases

because we are now adding so much sodium hydroxide, that there is not enough hydrochloric acid to react with it, this means that some of the sodium hydroxide does not react, so the amount of energy released by the reaction has reached a maximum

• in each experiment, we are adding a greater volume of solution • so the energy released is now spread out into a greater volume • because of this, when we add large volumes of sodium hydroxide, the maximum temperature reached decreases

• in the experiment we want to reduce heat loss as were measuring the temperature, and polystyrene is a good thermal insulator, reducing heat loss from the sides and the bottom • lid reduces heat lost by evaporation

1 . measure 50cm3 of