Chemical Energy: Definition and Examples

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Questions and Answers

What type of energy does chemical energy belong to?

Mechanical energy

Kinetic energy

Potential energy (correct)

Thermal energy

What is necessary for extracting chemical energy from propane?

High pressure environment

Presence of oxygen (correct)

Absence of bonds

Exposure to low temperatures

Which of the following substances does NOT contain chemical energy?

Food

Coal

Water (correct)

Gasoline

What happens to energy when new bonds are formed?

Energy is released Signup and view all the answers

What happens to propane molecules when they are exposed to heat?

They begin to vibrate and move Signup and view all the answers

How many water molecules are formed when a propane molecule is combusted?

4 Signup and view all the answers

What is required to break the bonds in chemical compounds?

Energy absorption Signup and view all the answers

Which of the following describes the nature of the energy released during the combustion of propane?

Greater than the energy required to break the bonds Signup and view all the answers

What is the primary result of combustion in relation to propane?

Formation of carbon dioxide and water Signup and view all the answers

Why is propane considered a useful source of chemical energy?

Because it releases a significant amount of energy upon combustion Signup and view all the answers

Which of the following is an example of an exothermic reaction?

The decomposition of food in a compost pile Signup and view all the answers

What is the primary source of energy for food?

Solar energy Signup and view all the answers

What is the main difference between endothermic and exothermic reactions?

Endothermic reactions require more energy than they release, while exothermic reactions release more energy than they require. Signup and view all the answers

Which of the following is NOT an example of chemical energy?

A rock Signup and view all the answers

What is the role of electrolytes in a battery?

To allow the flow of electrical charge Signup and view all the answers

What is the source of energy in petroleum?

Ancient marine organisms Signup and view all the answers

Why is the combustion of fossil fuels considered an exothermic reaction?

It releases more energy than it requires. Signup and view all the answers

Why is photosynthesis considered an endothermic reaction?

It requires more energy than it releases. Signup and view all the answers

How does the energy in food get transferred to our bodies?

Through chemical reactions Signup and view all the answers

What happens to the electrons in a battery during use?

They flow from the anode to the cathode. Signup and view all the answers

Study Notes

Chemical Energy Overview

Chemical energy is stored in the bonds of chemical compounds, including alkaline batteries, gasoline, coal, and food.
It is classified as potential energy, which is energy stored for use.
Energy is defined by scientists as the ability to perform work, divided into kinetic (motion-based) and potential (stored) forms.

Energy Release and Bond Formation

Breaking atomic bonds requires energy; forming new bonds releases energy.
Combustion (e.g., of gasoline) transforms stored energy into usable energy.
The process of burning propane demonstrates the potential energy release during combustion.
Exothermic reactions, such as combustion, release more energy than they consume.

Exothermic vs. Endothermic Reactions

Exothermic reactions (Greek: "exo" means outer; "therm" means heat) provide more energy than needed for bond breaking.
Examples: combustion of propane, wood, gasoline, and food decomposition in compost.
Endothermic reactions absorb energy and require more energy to break bonds than they release during bond formation.

Examples of Chemical Energy

Photosynthesis:
- Plants convert carbon dioxide and water into glucose using sunlight, storing energy in plant material.
- This process is endothermic, as it needs sunlight.
Petroleum:
- Formed from ancient marine organisms.
- An exothermic reaction upon combustion, releasing carbon dioxide and water while freeing significant energy.
Food:
- Energy from food traces back to the sun through the food chain.
- Digestion leads to exothermic reactions that release energy for bodily functions.
Batteries:
- Store chemical energy and convert it into electricity through reactions between metals and electrolytes.
- Electrons flow from anode to cathode, producing electricity.
Hand Warmers:
- Contain iron powder and salt; react with oxygen to produce heat through rust formation.
- The exothermic reaction yields more energy than the energy needed to initiate it.

Key Chemical Reactions

Balanced chemical reactions illustrate the transformation of reactants into products with associated energy changes.
Exothermic reactions are crucial for energy release in everyday applications like cooking and heating.
Endothermic reactions, although energy-absorbing, have practical uses like cooling in disposable ice packs.