Exothermic vs Endothermic

Exothermic vs Endothermic Processes

Mr Yepez

Lesson Objective

1. Compare and contrast endothermic and exothermic reactions.

Open Ended

Write down 1 difference between an exothermic and an endothermic process.

Combustion Reaction

1. Bonds are broken in the methane and oxygen molecules.

2. Bonds are formed in the carbon dioxide and water molecules.

Rusting of Iron 

Iron metal reacts with oxygen and water to form rust; a red-orange-brown substance on corroded iron. This chemical reaction releases a small amount of heat energy hence an exothermic process.

The equation of formation of rust can be represented as:

Multiple Select

Which are reactants in the rusting of iron?

• water

• iron

• heat

• oxygen

Chemical Equation

Iron+Oxygen+Water → Hydrated iron oxide + Heat

 4Fe + 3O₂ + 6H₂O → 4Fe(OH)₃ + heat

Ice Pack

- If you’ve ever sprained your ankle or fell from your bike, you've probably reached for an instant cold pack. This is a chemical reaction at play.

- In the bag, there are two components: water and ammonium nitrate. When the bag is broken up, water and ammonium nitrate mix.

- The reaction makes the water colder and the bag feel frosty and soothing on your swollen ankle.

Multiple Choice

In an endothermic reaction the heat is being absorbed, such as in photosynthesis. Thus, heat is said to be a:

• reactant

• product

Multiple Choice

What type of reaction was shown on the previous slide?

• endothermic

• exothermic

Dissolution of Ammonium Chloride in Water 

Example

Open Ended

What evidence is there to corroborate the assumption that this is an endothermic reaction?

The dissolution of ammonium chloride in water results in absorption of heat energy from the surrounding environment hence a drop in temperature of the solution.