Endothermic vs Exothermic Reactions

• Candle burning - gives out heat and light energy

• Battery - gives out electrical energy

• Firework - gives out light, heat, and sound

Some reactions give out energy:

• cooking an egg - takes heat from a source (stove)

• Photosynthesis - takes in energy from the sun to make glucose and oxygen

• Instant ice packs - absorbs heat from surroundings (why pack becomes cold)

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Some chemical reactions store (take in) energy:

• Reactions that take heat from in outside source

• Endo - bring INSIDE

• Baking cake - cake takes heat from the oven

Endothermic Reactions

• Reactions that give out heat

• Exo - heat EXITING

• Combustion - when things are on fire, you feel heat being released

Exothermic Reactions

• Combustion - reaction between fuel and oxygen that produces light and heat energy

• Cars run on combustion - engine burns fuel

• Lighting a match - striking the match, the chemicals stored on the head of the match begin to burn

• Harder to identify than Exothermic because they don't produce energy

• Require heat to be added in order to occur

• Some absorb heat from the environment, which then makes the surrounding area feel colder (heat moves from hot to cold)

Heating vs Cooling

• Temperature change from a reaction can change the temperature of the surrounding area (remember, heat moves)

• Energy absorbed during an endothermic reaction can be used to cool the surrounding area

  • example: instant ice pack (heat goes into the ice pack, ice pack feels cold)

• Energy released during an exothermic reaction can be used to heat the surrounding area

  • example: a hand warmer (chemicals in warmer produce heat)