RP 4 - Temperature Changes

• reaction

  neutralisation reaction between hydrochloric acid and sodium hydroxide - will add inc vol of sodium hydroxide solution to hydrochloric acid, and in each experiment measure max temp reached
• variables

  independent variable : volume of sodium hydroxide solution

  dependent variable : maximum temperature reached

  control variables : vol of hydrochloric acid, and concentrations of hydrochloric acid and sodium hydroxide solution
• method


  1. Use measuring cylinder to measure 30cm3 of dilute hydrochloric acid

  2. Transfer acid to polystryene cup and stand polystyrene cup inside a beaker - stops cup from falling over

  3. Use a thermometer to measure temperature of acid and record this in a table

  4. Use a measuring cylinder to measure 5cm3 of sodium hydroxide solution - transfer this to a polystyrene cup

  5. Fit a plastic lid the cup and place thermometer through hole of the lid - bulb of thermometer must be in solution

  6. Use the thermometer to gently stir the solution

  7. Observe exothermic reaction - temp will increase

  8. Look carefully at temp rise - when reading stops changing record highest temperature reached

  9. Rinse out polystryene cup and repeat experiment using 10cm3 sodium hydroxide solution and carry it out several more times each time inc vol of sodium hydroxide solution by 4cm3 until we reach maximum of 40cm3

  10. Repeat whole experiment 1 more time so we have two sets of results - use to calculate mean value for maximum temperature reached
• Increasing volume of sodium hydroxide solution

  Maximum temperature reached increases
• Adding more particles of sodium hydroxide


  They react with hydrochloric acid
• Exothermic reaction


  More energy is released
• Increasing volume of sodium hydroxide solution

  Maximum temperature reached starts to decrease
• Excess sodium hydroxide


  Some unable to react
• Amount of energy reached at a maximum
• Increasing volume of solution

  Temperature decreases
• why do we use a polystryene cup with a lid?

  • want to reduce any heat losses as we are measuring the temperature
  • polystryene good thermal insulator - reduces heat loss to sides and bottom
  • lid - reduces heat loss to the air