Chemical energy is a form of potential energy stored in the bonds between atoms and molecules within substances. It is released or absorbed during chemical reactions.
The general formula for the chemical energy stored in a substance is not as straightforward as some other forms of energy. However, during a chemical reaction, the change in chemical energy (ΔE) can be calculated using the formula:
ΔE=q+w
where q is the heat exchanged and w is the work done.
The unit of energy is typically expressed in joules (J) for chemical energy.
Examples of Chemical Energy
- Burning wood releases approximately 15,000,000 J of chemical energy.
- A typical alkaline battery in a flashlight may store about 9,000 J of chemical energy.
- During the photosynthesis process, a plant may store 200 J of chemical energy in a glucose molecule.
- Burning 1 gallon of gasoline releases approximately 131,000,000 J of chemical energy.
- The chemical energy in a 100g serving of carbohydrates is approximately 1,680 J.
- TNT (trinitrotoluene) releases about 4,184,000 J of chemical energy per kilogram during detonation.
- Burning 1 cubic meter of natural gas releases around 37,000,000 J of chemical energy.
- A hydrogen fuel cell can convert chemical energy into electrical energy, releasing 286,000 J per mole of hydrogen.
- The metabolic process releases chemical energy, and a person may consume 8,700 kJ of energy per day.
- Burning 1 ton of coal releases approximately 24,000,000,000 J of chemical energy.
Exam Related Questions
| Numbering | Questions | Answers |
|---|---|---|
| 1. | What is chemical energy, and where is it stored? | Chemical energy is potential energy stored in the bonds of atoms and molecules. It is stored in substances and released during chemical reactions. |
| 2. | Provide an example of a daily activity that involves the release of chemical energy. | Cooking food, where the combustion of natural gas or the breakdown of carbohydrates in food releases chemical energy. |
| 3. | Explain the difference between potential energy and chemical energy. | Potential energy is stored energy due to an object’s position, while chemical energy is stored in the bonds between atoms and molecules. |
| 4. | How is chemical energy related to the process of photosynthesis in plants? | Photosynthesis converts light energy into chemical energy stored in glucose molecules. |
| 5. | During the combustion of gasoline in a car engine, what form of energy is released? | Chemical energy stored in gasoline is converted into thermal and kinetic energy. |
| 6. | What is the unit of measurement for chemical energy, and how is it typically expressed? | The unit is the joule (J), and chemical energy is typically expressed in joules. |
| 7. | Describe a chemical reaction where the chemical energy of the reactants is converted into thermal energy. | Combustion reactions, such as burning wood, release chemical energy as heat. |
| 8. | How does the combustion of natural gas contribute to the production of energy for homes? | Burning natural gas releases chemical energy, providing heat energy for heating homes and cooking. |
| 9. | Discuss the role of chemical energy in the functioning of batteries. | Batteries store chemical energy, and during a reaction, this energy is converted into electrical energy. |
| 10. | In the context of explosives, explain how chemical energy is released during detonation. | During detonation, chemical bonds in explosives break, releasing a large amount of stored chemical energy rapidly. |
