Heat Energy Changes Flashcards
All 7 cards in this deck
What is an exothermic change or reaction?
One in which heat energy is given out (released to the surroundings), so the temperature rises.
e.g. a hand warmerWhat is an endothermic change or reaction?
One in which heat energy is taken in (absorbed) from the surroundings, so the temperature falls.
e.g. a cold packName four types of change in solution that are accompanied by heat energy changes.
Salts dissolving in water, neutralisation reactions, displacement reactions and precipitation reactions.
How is the temperature change worked out when a solid dissolves in water in a polystyrene cup?
Temperature change = final temperature − initial temperature (in °C). A rise means the change is exothermic; a fall means it is endothermic.
Why is a polystyrene cup used instead of a glass beaker when measuring a temperature change?
Polystyrene is a good heat insulator (poor conductor of heat), so it reduces heat energy transfer.
True or false? An exothermic reaction always gives out light.
False. An exothermic reaction always gives out heat energy; it does not have to give out light, sound or a gas.
Is dissolving ammonium chloride in water endothermic or exothermic?
Endothermic: it takes in heat energy, so the temperature of the solution falls.