Temperature Changes

• Temperature Changes Method:

  • use a measuring cylinder to measure a set volume of hydrochloric acid into a polystyrene cup
  • measure the temperature of the acid and using a thermometer and record
  • measure a set volume of sodium hydroxide solution and transfer to the cup
  • mix the reagents
  • put a lid on and insert thermometer through the lid
  • monitor temperature increase and record maximum temperature
  • calculate the change in temperature
  • repeat using different volumes of sodium hydroxide solution
  • repeat 3 times for each volume and calculate a mean
  • plot a graph
• Temperature Changes Method:

  • measure a set volume of hydrochloric acid and put into a polystyrene cup
  • measure the temperature of the acid and record in a table
  • measure a set volume of sodium hydroxide solution and add it
  • mix the reagents
  • put a lid on the cup and insert a thermometer through the lid
  • monitor the temperature increase and record maximum temperature
  • calculate the temperature change
  • repeat 3 times and calculate a mean
  • repeat for different volumes of sodium hydroxide solution
  • plot a graph
• The dependent variable for the temperature changes practical is he maximum temperature reached.
• A source of error in the temperature changes practical could be incorrect thermometer reading, incorrect measurement of acid or an incorrect measurement of alkali.
• The independent variable for the temperature changes practical is the volume of sodium hydroxide solution.
• A polystyrene cup with a lid is used because polystyrene is a good thermal insulator so it reduces heat loss through the sides and bottom of the cup. The lid reduces heat loss to the air.
• The temperature change reaches a maximum because once the sodium hydroxide is in excess, no further heat energy is released (hydrochloric acid is the limiting reactant).
• It is important to mix the reagents fully so the reagents react fully or to distribute the heat.
• A digital thermometer could be used to increase reliability as it is easier to read.
• Once the reaction is complete, the temperature will decrease because energy is lost to the surroundings so it cools back to room temperature.