Chemical Energy and Reactions Overview

Study Notes

Chemical Energy Definition

Chemical energy is energy stored within the bonds of chemical compounds.
Examples include batteries, gasoline, coal, and food.
Classified as potential energy, not kinetic energy.

How Chemical Energy Works

Breaking chemical bonds requires energy. Forming new bonds releases energy.
Chemical transformations involve understanding the chemistry of the substances involved.

Propane Combustion Example

Propane (a molecule made of carbon and hydrogen) has chemical energy.
Combustion involves heat; atoms vibrate and move rapidly.
Propane molecules break apart, reforming into carbon dioxide and water.
The energy released from forming new bonds is greater than the energy required to break the original bonds.
This is an exothermic reaction (releases more energy than it consumes).
Balanced reaction example provided showing propane combustion.

Exothermic vs. Endothermic Reactions

Exothermic: Reactions release more energy than they absorb.
Examples include propane combustion, burning wood, gasoline combustion, and decomposing food.
Endothermic: Reactions absorb more energy than they release.
Energy is taken from the system.
Example: disposable ice packs (ammonium nitrate and water reaction)

Chemical Energy Examples and Applications

Photosynthesis:
- Plants store chemical energy through endothermic reactions.
- Collects carbon dioxide and water, reformats them into glucose, and releases oxygen (Photosynthesis)
- Energy required comes from the sun.
Petroleum:
- Fossil fuels (petroleum) store energy from ancient organisms.
- Combustion reaction is exothermic (releases more energy).
- Products are carbon dioxide and water.
Food:
- Energy in food (chemical energy) originates from the sun.
- Energy from converting food is used to power the body.
- The digestion process (breaking and forming bonds) is exothermic.
Batteries:
- Store chemical energy to produce electricity.
- Electrolytes and metals react, liberating electrons.
- Electrons flow through a wire (electricity).
Hand Warmers:
- Contain iron powder, water, salt, and absorbent material.
- Exothermic reaction produces heat when exposed to air.
- Iron reacts with oxygen (forming rust) to generate heat.

Description

This quiz covers the fundamentals of chemical energy, including its definition, how it works, and the differences between exothermic and endothermic reactions. You'll explore examples such as propane combustion to understand energy transformations in chemical processes.