RP04 - Temperature Change

• What is the first step of the temperature change practical?

  Use a measuring cylinder to measure 30 cm³ of hydrochloric acid.
• What is the second step of the temperature change practical?

  Pour the acid into a polystyrene cup placed inside a beaker for stability.
• What is the third step of the temperature change practical?

  Put a lid on the cup and place a thermometer through the hole in the lid.
• What is the fourth step of the temperature change practical?

  Record the starting temperature of the acid.
• What is the fifth step of the temperature change practical?

  Measure 5 cm³ of sodium hydroxide solution using a clean measuring cylinder.
• What is the sixth step of the temperature change practical?

  Add the sodium hydroxide to the acid, stir gently with the thermometer, and record the highest temperature reached.
• What is the seventh step of the temperature change practical?

  Repeat the experiment, adding 5 cm³ more sodium hydroxide each time (e.g., 10 cm³, 15 cm³...) up to a total of 40 cm³.
• What type of reaction is this an example of?

  An exothermic reaction – it releases heat energy.
• Why is a polystyrene cup used in this experiment?

  It is a good insulator and reduces heat loss to the surroundings.
• Why is a lid used during the experiment?

  To reduce heat loss and improve the accuracy of the temperature change measurement.
• Why do we stir the mixture with the thermometer?

  To ensure the reaction mixture is evenly heated, giving a reliable temperature reading.
• What safety precautions should be taken in this practical?

  Wear goggles – sodium hydroxide and hydrochloric acid are corrosive.
• How can you reduce human error when reading the thermometer?

  Keep your eye level with the liquid and read the bottom of the meniscus.