Required Practical 4: Temperature Changes

• What should you be able to describe by the end of the video?

  How to investigate the variables that affect temperature changes in chemical reactions
• What type of reaction is being investigated in this practical?

  An exothermic reaction
• What is the neutralization reaction being studied?

  The reaction between hydrochloric acid and sodium hydroxide
• What is the independent variable in this experiment?

  The volume of sodium hydroxide solution
• What is the dependent variable in this experiment?

  The maximum temperature reached
• What are the control variables in this experiment?

  The volume of hydrochloric acid and the concentrations of both solutions
• How do you prepare the hydrochloric acid for the experiment?

  Measure 30 centimeters cubed of dilute hydrochloric acid
• Why do we place the polystyrene cup inside a beaker?

  To prevent the cup from falling over
• What should you do after adding sodium hydroxide solution to the polystyrene cup?

  Fit a plastic lid and place the thermometer in the solution
• What happens to the temperature of the solution during the exothermic reaction?

  The temperature of the solution increases
• What do you record when the thermometer reading stops changing?

  The highest temperature reached
• How do you repeat the experiment after the first trial?

  Use 10 centimeters cubed of sodium hydroxide solution
• What is the maximum volume of sodium hydroxide solution used in the experiment?

  40 centimeters cubed
• What trend is observed when increasing the volume of sodium hydroxide solution?

  The maximum temperature reached increases initially
• Why does the maximum temperature start to decrease after a certain volume of sodium hydroxide?

  There is not enough hydrochloric acid to react with all the sodium hydroxide
• What happens to the energy released when large volumes of sodium hydroxide are added?

  The energy is spread out into a greater volume
• Why is a polystyrene cup with a lid used in this experiment?

  To reduce heat loss during the temperature measurement
• What is the property of polystyrene that makes it suitable for this experiment?

  It is a good thermal insulator
• What are the steps involved in the experiment to investigate temperature changes in an exothermic reaction?

  1. Measure 30 cm³ of dilute hydrochloric acid.
  2. Transfer to a polystyrene cup.
  3. Measure initial temperature.
  4. Add 5 cm³ of sodium hydroxide solution.
  5. Fit a lid and insert thermometer.
  6. Stir gently and record highest temperature.
  7. Repeat with increasing volumes of sodium hydroxide.
  8. Calculate mean maximum temperature for each volume.
  9. Plot a graph of results.
• What are the key observations from the experiment regarding temperature changes?

  • Maximum temperature increases with more sodium hydroxide.
  • Temperature decreases after a certain volume due to insufficient hydrochloric acid.
  • Energy released is spread over a larger volume with excess sodium hydroxide.
• What resources can be used for additional questions on this practical?

  • Vision workbook
  • Online resources linked in the video