Temperature changes rq

• What is the first step in the procedure for the experiment?

  Use a measuring cylinder to measure 30cm³ of dilute hydrochloric acid.
• Why is the polystyrene cup placed inside a beaker?

  To stop the polystyrene cup from falling.
• What should be used to measure the temperature of the acid?

  A thermometer.
• How should the temperature of the acid be recorded?

  Record it on a table.
• What is the purpose of fitting a plastic lid onto the cup?

  To place a thermometer through a hole in the lid and gently stir the solution.
• What type of reaction occurs when sodium hydroxide is added to hydrochloric acid?

  The reaction is exothermic, releasing energy.
• What should be done when the thermometer stops rising?

  Record the highest temperature reached.
• What should be done after rinsing and drying the polystyrene cup?

  Repeat the experiment several more times, increasing the volume of sodium hydroxide solution by 5cm³ until 40cm³.
• Why is it important to repeat the whole experiment one more time?

  To have 2 sets of results for calculating the mean value and plotting a graph.
• What are the steps involved in the experiment?

  1. Measure 30cm³ of dilute hydrochloric acid.
  2. Transfer into a polystyrene cup.
  3. Place the cup inside a beaker.
  4. Measure and record the temperature of the acid.
  5. Measure 5cm³ of sodium hydroxide solution.
  6. Transfer into the polystyrene cup.
  7. Fit a plastic lid and stir with a thermometer.
  8. Record the highest temperature after the reaction.
  9. Rinse and dry the cup, then repeat with increasing sodium hydroxide volumes.

  10. Repeat the entire experiment for two sets of results.
• What is the significance of the exothermic reaction in this experiment?

  • It indicates that energy is released during the reaction.
  • It causes an increase in temperature, which can be measured.
  • It helps in understanding the nature of acid-base reactions.
• As we increase the volume of sodium hydroxide solution the maximum temperature increases

  Because when we add more particles of sodium hydroxide they react with hydrochloric acid
• However at a certain volume of sodium hydroxide solution the maximum temperature reached starts to decrease

  At this point, there is too much sodium hydroxide that there is not enough hydrochloric acid- some of the sodium hydroxide is unable to react (reached a maximum)
• Polystyrene is a good thermal insulator- reduces heat loss to the air
• Independent variable:

  • Volume of sodium hydroxide solution
• Dependant variable:

  • Maximum temperature reached
• Control variable:

  • Volume of hydrochloric acid
  • Concentration of both sodium hydroxide solution and hydrochloric acid