Prescribed practical C3 - Temperature changes during a reaction
Method
- Place the polystyrene cup into the 250 cm3 beaker to stabilise it.
- Carefully measure 25 cm3 of hydrochloric acid and place it in the polystyrene cup.
- Take the initial temperature of the hydrochloric acid and record it in the results table.
- Wash out the measuring cylinder and rinse it with a little sodium hydroxide solution.
- Then measure 25 cm3 of sodium hydroxide solution into the measuring cylinder.
- Add the sodium hydroxide solution to the acid, stir with the thermometer, measure and record the highest temperature reached during the reaction.
| Initial temperature of hydrochloric acid / °C | Highest temperature reached in reaction / °C | Temperature change / °C |
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| Initial temperature of hydrochloric acid / °C | â ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Ä |
|---|---|
| Highest temperature reached in reaction / °C | â ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Ä |
| Temperature change / °C | â ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Äâ ¶Ä |
During this reaction the H+ ions from the acid and the OH- ions from the alkali react together to form water. As this happens, energy is released which is detected by the thermometer. The term we use to describe the release of energy is a chemical reaction is exothermic (the ‘exit’ of energy).