Grade 7
  1. Introduction to Chemistry  1.1. What is Chemistry?  1.2. Importance of chemistry in daily life  1.3. Branches of chemistry  1.4. Scientific Method in Chemistry  1.5. Laboratory Safety Rules and Precautions  1.6. Common Laboratory Equipment and Their Uses  1.7. Units of measurement in chemistry
  2. Matter and its properties  2.1. Definition of Matter  2.2. Classification of matter  2.3. Properties of matter  2.3.1. Physical properties  2.3.2. Chemical properties  2.4. States of matter  2.4.1. Solid state  2.4.2. Fluid state  2.4.3. Gaseous state  2.4.4. Plasma and Bose–Einstein condensates  2.5. Changes in the states of matter  2.5.1. Melting and freezing  2.5.2. Evaporation and Condensation  2.5.3. Sublimation and deposition  2.6. Density and its applications  2.7. Diffusion and its importance
  3. Elements, Compounds, and Mixtures  3.1. Definition of the element  3.2. Classification of elements  3.3. Metals, Nonmetals and Metalloids  3.4. Noble gases and their properties  3.5. Introduction to the Periodic Table  3.6. Definition of Compound  3.7. Properties of Compounds  3.8. Introduction to Chemical Formulas  3.9. Definition of Mixture  3.10. Types of mixtures  3.10.1. Homogeneous mixture  3.10.2. Heterogeneous mixtures  3.11. Difference Between Compounds and Mixtures  3.12. Solutions, Colloids and Suspensions
  4. Separation of mixtures  4.1. Need for separation of mixtures  4.2. Separation methods  4.2.1. Filtration  4.2.2. Sedimentation and decantation  4.2.3. Evaporation  4.2.4. Crystallization  4.2.5. Distillation  4.2.6. Chromatography  4.2.7. Magnetic Separation  4.2.8. Centrifugation
  5. Atomic Structure  5.1. Introduction to Atoms  5.2. Structure of the atom  5.2.1. Nucleus and electron cloud  5.3. Subatomic particles  5.3.1. Proton  5.3.2. Neutron  5.3.3. Electrons  5.4. Atomic number and mass number  5.5. Isotopes and their uses  5.6. Ions and ion formation
  6. Periodic table  6.1. Introduction to the Periodic Table  6.2. Groups and periods  6.3. Trends in the Periodic Table  6.3.1. Atomic Size  6.3.2. Metallic and non-metallic character  6.3.3. Electronegativity  6.3.4. Reactivity of the elements  6.4. Alkali metals and their properties
  7. Chemical bond  7.1. Why do atoms form bonds?  7.2. Types of chemical bonds  7.2.1. Ionic bond  7.2.2. Covalent bond  7.2.3. Metal Bond  7.3. Properties of Ionic and Covalent Compounds  7.4. Intermolecular forces
  8. Chemical reactions  8.1. Introduction to Chemical Reactions  8.2. Signs of a chemical reaction  8.3. Types of Chemical Reactions  8.3.1. Combination Reactions  8.3.2. Decomposition reactions  8.3.3. Displacement reactions  8.3.4. Double displacement reactions  8.3.5. Combustion reactions  8.4. Law of conservation of mass  8.5. Balancing simple chemical equations
  9. Acids, Bases and Salts  9.1. Definition of Acid and Base  9.2. Properties of Acids  9.3. Properties of bases  9.4. pH Scale and Indicators  9.5. Neutralization reactions  9.6. Common Acids and Bases in Everyday Life  9.7. Preparation and use of salts  9.8. Strong and weak acids and bases
  10. Solutions and Solubility  10.1. Definition of Solution  10.2. Components of the solution  10.2.1. Solvent  10.2.2. solute  10.3. Factors Affecting Solubility  10.4. Concentration of solutions  10.5. Saturated and unsaturated solutions  10.6. Colloids and suspensions  10.7. Solubility curve and its interpretation
  11. Air and atmosphere  11.1. Composition of air  11.2. Properties of gases in the air  11.3. Importance of Oxygen and Carbon Dioxide  11.4. Air pollution and its effects  11.5. Greenhouse effect and global warming  11.6. Ways to reduce air pollution  11.7. Ozone layer and its importance
  12. Water and its importance  12.1. Properties of Water  12.2. Water as the universal solvent  12.3. Importance of water for life  12.4. Water pollution and its effects  12.5. Water Purification  12.5.1. Filtration  12.5.2. boil  12.5.3. Chlorination in water purification  12.5.4. reverse osmosis  12.6. Hard and soft water  12.7. Water cycle and its importance
  13. Fuel and energy  13.1. Types of fuel  13.1.1. Fossil fuels  13.1.2. Renewable energy sources  13.2. Combustion and energy release  13.3. Global warming and its effects  13.4. Alternative sources of energy  13.5. Ways to conserve energy
  14. Metals and Nonmetals  14.1. Physical and chemical properties of metals  14.2. Physical and Chemical Properties of Non-Metals  14.3. Difference Between Metals and Nonmetals  14.4. Uses of metals and nonmetals  14.5. Corrosion of metals and its prevention  14.6. Alloys and their importance
  15. Plastics and polymers  15.1. Natural and synthetic polymers  15.2. Properties of plastics  15.3. Biodegradable and Non-Biodegradable Plastics  15.4. Environmental impact of plastic  15.5. Recycling and waste management in plastics and polymers  15.6. Daily Uses of Polymers
  16. Introduction to Organic Chemistry  16.1. Basic definitions of organic chemistry  16.2. Carbon Compounds in Daily Life  16.3. Hydrocarbons  16.4. Simple functional groups (alcohols and carboxylic acids)  16.5. Importance of organic compounds in industry

Grade 7 → Fuel and energy ↓


Combustion and energy release


Combustion is a very important chemical process that is part of our daily lives. It is the process of burning something, in which a substance reacts with oxygen to produce heat and light. Combustion is a type of chemical reaction that releases energy.

What is combustion?

Combustion is a reaction in which a substance, usually a fuel, combines with oxygen to form carbon dioxide, water, and energy. This energy can be in the form of heat and light. When wood burns in a campfire, the process that causes the wood to turn into ash and release energy in the form of heat and light is called combustion.

How does combustion work?

Combustion requires three elements. This is often called the "fire triangle" and includes fuel, oxygen, and heat.

  • Fuel: This is any material that can be burned to produce energy. Common fuels include wood, gas, and charcoal.
  • Oxygen: Oxygen is a gas in the air that helps things burn. Combustion cannot occur without enough oxygen.
  • Heat: Heat is needed to start the reaction. It provides the energy needed to begin the reaction between fuel and oxygen. Once combustion begins, it produces more heat, which helps keep the process going.

A simple way to think about combustion is to imagine burning a candle. The candle's wax is the fuel. The wick burns, providing the heat needed to start combustion. Oxygen in the air surrounds the flame and helps the wax burn, giving off light and heat.

Example of a combustion reaction

The chemical reaction for combustion of propane, a common fuel used in heating and cooking, is as follows:

        C3H8 + 5O2 → 3CO2 + 4H2O + energy

In this reaction, propane (C3H8) reacts with oxygen (O2) to produce carbon dioxide (CO2), water (H2O), and energy.

Types of combustion

There are different types of combustion depending on the mode of reaction:

  • Complete combustion: This occurs when there is adequate oxygen available, and the fuel burns completely, producing a blue flame and the maximum amount of heat. The products are usually carbon dioxide and water. A clean gas stove burner indicates complete combustion.
  • Incomplete combustion: This occurs when there is not enough oxygen available. This creates carbon monoxide, which is a poisonous gas, as well as carbon (soot) and less energy. A yellow flame in a candle indicates incomplete combustion.
  • Rapid combustion: This type of combustion occurs quickly and produces large amounts of heat and light, such as in fireworks.
  • Slow combustion: It occurs slowly and produces less heat. An example of this is the slow rusting of iron.

Energy released during combustion

One of the main reasons combustion is important is that it releases energy. The energy released during combustion can be used in several ways:

  • Heat energy: This is the energy that keeps us warm when we burn wood in a fireplace or use a heater that runs on natural gas.
  • Light energy: Combustion gives us candlelight or a campfire.
  • Mechanical energy: The energy produced by the combustion of gasoline in a car engine powers the movement of the vehicle.

Visualizing combustion: An example

Wood as fuel

In the simple illustration above, the brown rectangle represents the piece of wood that serves as fuel. The orange triangle above represents the flame produced when the wood burns, demonstrating the process of combustion, which releases heat and light.

Real-life applications

Combustion is important in many aspects of daily life. Here are some areas where combustion is necessary:

  • Transportation: Combustion is the reason cars, airplanes, ships, and trains move. Vehicles often use fuels such as gasoline or diesel that combust to power the engine and create motion.
  • Heating: Many heating systems in homes use the combustion of natural gas or oil to produce heat during cold weather.
  • Electricity generation: Power plants can burn coal or natural gas to generate electricity by converting heat into mechanical energy and then into electrical energy.
  • Cooking: Stoves and ovens that use natural gas or propane rely on combustion to generate the heat needed for cooking.

Important safety and environmental considerations

Although combustion is useful, it requires safety precautions because of its potential hazards:

  • Carbon monoxide hazard: Incomplete combustion can produce carbon monoxide, which is dangerous if inhaled. Good ventilation is a must when using combustion appliances indoors.
  • Fire hazard: Uncontrolled combustion can cause fires that can damage property and harm people. It is essential to handle fuel with care.
  • Environmental impact: The combustion of fossil fuels releases carbon dioxide, a greenhouse gas that contributes to climate change. Finding ways to reduce emissions is an ongoing challenge.

Search for alternative fuels

To address environmental concerns, scientists are exploring alternative fuels that allow cleaner combustion. Some innovative options include:

  • Biofuels: These are derived from plant or animal matter and can reduce dependence on fossil fuels.
  • Hydrogen: A clean fuel that produces only water when burned, but requires energy to produce efficiently.
  • Electricity: Although electric vehicles do not burn fuel, they reduce reliance on internal combustion engines, thus reducing emissions.

Conclusion

Combustion is an essential chemical process that facilitates most of the energy and heat we use in our daily lives. While combustion has distinct advantages, considerations for safety and the environment are paramount. As the world continues to develop and explore alternative energy sources, understanding the role of combustion becomes even more important.


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