RQO 4: temp change

• rqp 1

  using a measuring cylinder, measure 30cm3 of dilute hydrochloric acid

  transfer this into a polystyrene cup, and stand this into a beaker (to stop it from falling over)

  use a thermometer to measure the temp of acid and record
• rqp2

  using a measuring cylinder, measure 5cm3 of sodium hydroxide solution and transfer into the polystyrene cup
• rqp3

  add a plastic lid to the cup and place the thermometer through a hole in lid, ensuring the bulb is in the solution
• rqp 4

  stir with the themometer

  since it is an exothermic reaction, energy will be released, so the temp will increase

  when the reading stops changing, record the highest temp reached
• rqp 5

  rinse and dry the cup, repeat with 10cm3 if sodium hydroxide solution, and do this several times whilst increasing the volume of sodium hydroxide solution by 5cm3 each time until 40cm3
• rqp 6

  repeat all again to get 2 sets of results and calculate a mean
• indépendant variable = volume of sodium hydroxide solution
• dependant variable = maximum temperature reached
• control variable:

  • volume of hydrochloric acid
  • concentration of hydrochloric acid and sodium hydroxide solution
• 1 :

  increasing the volume of sodium hydroxide solution increases the max temp as more particles reacting means more energy released
• 2: at a certain volume, the Max temp decreases as there is too much sodium hydroxide and not enough hydrochloric acid so some of the sodium hydroxide is unable to react so the maximum energy has been released

  this decreases as the energy released is spread over a greater volume

  
• polystyrene cup is used as it is a good thermal insulator so it reduces heat loss from the sides and bottom

  a plastic lid is used to reduce heat loss from the air