Copy of Exothermic & Endothermic Reactions

Chemical Reactions

• Chemical reactions can be categorized based on their heat flow:

  • Exothermic Reactions: Release heat (e.g., burning of paper).

  • Endothermic Reactions: Absorb heat (e.g., browning of a pizza).

Reactants and Products

• A reactant is a substance that undergoes a chemical change in a reaction.

• A product is the substance formed as a result of a chemical reaction.

• Chemical reactions involve:

  • Breaking existing chemical bonds in the reactants

  • Forming new chemical bonds in the products

  • Chemical bonds contain chemical energy.

Types of Reactions

Exothermic Reactions

• In an exothermic reaction, the energy released from product formation is greater than the energy required to break reactant bonds.

• Characteristics:

  • Release thermal energy, heat, and light.

Endothermic Reactions

• In an endothermic reaction, more energy is needed to break the bonds of reactants than what is released during product formation.

• Characteristics:

  • Absorb thermal energy, heat, and light.

Group Discussion Examples

Exothermic Reactions

• Example 1: Light is released from a light bulb or star.

• Example 3: Burning natural gas.

• Example 5: Burning reaction of a candle.

Endothermic Reactions

• Example 2: Requires a continuous source of energy.

• Example 4: Frying an egg in a pan.

• Example 6: Ice melting to form water.