Reactions and temperature changes
Exothermic and endothermic reactions
When a fuel burns, the surroundings become warmer. The capacity of a system to do work or the quantity required for mechanical work to take place. Measured in joules (J). For example, a man transfers 100 J of energy when moving a wheelbarrow. is transferred to the surroundings. This is an example of an Reaction in which energy is given out to the surroundings. The surroundings then have more energy than they started with so the temperature increases. reaction.
During some reactions, energy is transferred from the surroundings. This is called an Reaction in which energy is taken in. reaction.
In endothermic reactions, energy enters. In exothermic reactions, energy exits.
Temperature change
For some reactions, it is possible to measure the temperature of the A substance that reacts together with another substance to form products during a chemical reaction. at the start and the temperature of the A substance formed in a chemical reaction. at the end.
The change in temperature indicates how exothermic or endothermic the reaction is.
| Change | Reaction type |
| Increase in temperature | Exothermic |
| Decrease in temperature | Endothermic |
| Change | Increase in temperature |
|---|---|
| Reaction type | Exothermic |
| Change | Decrease in temperature |
|---|---|
| Reaction type | Endothermic |
The slideshow describes an exothermic reaction between dilute sodium hydroxide and hydrochloric acid, and an endothermic reaction between sodium carbonate and ethanoic acid.
Image caption, 1. Sodium hydroxide solution is poured into a beaker of hydrochloric acid which contains a thermometer showing room temperature
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A study of the energy changes involved in chemical reactions, whether exothermic or endothermic