Heat Energy Changes Flashcards
All 6 cards in this deck
What is an exothermic reaction or change?
One in which heat energy is given out to the surroundings, so the temperature of the surroundings rises.
What is an endothermic reaction or change?
One in which heat energy is taken in from the surroundings, so the temperature of the surroundings falls.
Name four types of change that are accompanied by heat energy changes measurable as a temperature change in solution.
Salts dissolving in water, neutralisation reactions, displacement reactions and precipitation reactions.
What are the steps to measure the temperature change of a reaction in solution?
e.g. dilute hydrochloric acid neutralised by sodium hydroxide solution
- Measure a fixed volume of the acid into a polystyrene cup and record its starting temperature.
- Add the sodium hydroxide solution and stir.
- Record the highest (or lowest) temperature reached; temperature change = final − starting temperature.
In an experiment measuring a temperature change in solution, how can heat loss be reduced?
Put a lid on the cup and insulate it (e.g. cotton wool), so less heat energy escapes to the surroundings.
True or false? If the temperature of the solution falls during a reaction, the reaction is exothermic.
False. A temperature fall means heat energy has been taken in, so the reaction is endothermic.