Grade 10
  1. Matter and its properties  1.1. States of matter  1.2. Physical and chemical properties of matter  1.3. Classification of substances (elements, compounds, mixtures)  1.4. Changes in Matter (Physical and Chemical Changes)  1.5. Law of conservation of mass and law of definite proportions
  2. Atomic Structure  2.1. Historical development of the atomic model  2.2. Subatomic particles (protons, neutrons, electrons)  2.3. Atomic number, mass number and isotopes  2.4. Electronic Configuration and Energy Levels  2.5. Valency, ion formation and oxidation state
  3. Periodic table  3.1. History and Development of the Periodic Table  3.2. Modern Periodic Law and Periodic Trends  3.3. Groups and Periods in the Periodic Table  3.4. Trends in the Periodic Table  3.5. Metals, non-metals, metalloids and their properties  3.6. Noble gases and their chemical inertness
  4. Chemical bond  4.1. Formation of Chemical Bonds (Octet Rule)  4.2. Ionic Bonding and Properties of Ionic Compounds  4.3. Covalent Bond and Properties of Covalent Compounds  4.4. Metallic bond and its properties  4.5. Molecular geometry and VSEPR theory  4.6. Polarity and dipole moment of molecules  4.7. Intermolecular forces
  5. Chemical Reactions and Equations  5.1. Types of Chemical Reactions  5.2. Writing and balancing chemical equations  5.3. Law of conservation of mass in chemical reactions  5.4. Factors Affecting Chemical Reactions  5.5. Catalysts and their role in chemical reactions  5.6. Exothermic and Endothermic Reactions
  6. Stoichiometry and Chemical Calculations  6.1. Mole concept and Avogadro number  6.2. Molar Mass and Gram-Mole Conversions  6.3. Empirical and molecular formula  6.4. Stoichiometric calculations and chemical yield  6.5. Limiting and Excess Reactants
  7. Acids, Bases and Salts  7.1. Properties and Definitions of Acids and Bases (Arrhenius, Bronsted-Lowry, Lewis)  7.2. pH Scale, pOH, and Indicators  7.3. Neutralization reactions and salt formation  7.4. Strength of Acids and Bases (Strong vs. Weak Acids and Bases)  7.5. Common Acids and Bases in Daily Life  7.6. Salts, their solubility and applications
  8. Metals and Nonmetals  8.1. Physical and chemical properties of metals  8.2. Physical and Chemical Properties of Non-Metals  8.3. Reactivity Series of Metals and Displacement Reactions  8.4. Extraction of metals from ores  8.5. Corrosion, its causes and prevention  8.6. Alloys, their composition and uses
  9. Carbon and its compounds  9.1. Allotropes of Carbon  9.2. Hydrocarbons and their classification (alkanes, alkenes, alkynes)  9.3. Functional groups in organic compounds  9.4. Nomenclature of organic compounds (IUPAC system)  9.5. Isomerism in organic chemistry (structural and geometrical)  9.6. Important organic reactions (combustion, addition, substitution, polymerization)  9.7. Applications of organic compounds in industry and daily life
  10. Environmental Chemistry  10.1. Air Pollution (Sources, Effects and Control)  10.2. Water Pollution (Causes, Effects and Remedies)  10.3. Greenhouse effect and global warming  10.4. Ozone layer depletion and its effects  10.5. Green Chemistry and Its Applications  10.6. sustainable chemistry practice
  11. Thermochemistry  11.1. Heat and Energy Changes in Chemical Reactions  11.2. Exothermic and Endothermic Reactions  11.3. Enthalpy, enthalpy change, and heat of reaction  11.4. Specific heat capacity and calorimetry  11.5. Energy Changes in Combustion Reactions
  12. Electrochemistry  12.1. Electrolytes and non-electrolytes  12.2. Electrolysis and its applications (electroplating, extraction of metals)  12.3. Redox reactions (oxidation and reduction)  12.4. Galvanic cell and electrochemical series  12.5. Corrosion and electrochemical prevention methods
  13. Chemical kinetics and equilibrium  13.1. Rate of chemical reactions and its measurement  13.2. Factors affecting the reaction rate (catalyst, temperature, concentration)  13.3. Reversible and irreversible reactions  13.4. Dynamic equilibrium and equilibrium constant  13.5. Le Chatelier's principle and its applications
  14. Gases and Gas Laws  14.1. Properties of gases and kinetic molecular theory  14.2. Boyle's Law (Pressure-Volume Relation)  14.3. Charles's Law  14.4. Gay-Lussac's Law  14.5. Combined Gas Law and Ideal Gas Law  14.6. Real Gases vs Ideal Gases
  15. Nuclear Chemistry  15.1. Introduction to Radioactivity and Nuclear Reactions  15.2. Types of radioactive decay (alpha, beta, gamma)  15.3. Half-life and applications of radioactive isotopes  15.4. Nuclear fission and fusion reactions  15.5. Nuclear power generation and its environmental impact

Grade 10 → Thermochemistry ↓


Energy Changes in Combustion Reactions


In chemistry, one of the most important aspects is to understand how energy changes during chemical reactions. In this document, we will explore combustion reactions. Combustion reactions are a type of chemical reaction where a substance combines with oxygen and releases energy. This energy is often in the form of heat and light.

What is a combustion reaction?

The combustion reaction is a chemical process in which fuel reacts with oxygen (O2) to produce carbon dioxide (CO2), water (H2O), and energy. These reactions are usually exothermic, which means they release energy. Here's a basic equation for a combustion reaction:

Fuel + O2 → CO2 + H2O + Energy

The energy released during combustion is usually in the form of heat and light. This is why we see flames and feel heat when substances such as wood or gasoline burn.

Types of combustible fuel

There are different types of fuels that undergo combustion reactions, and these include:

  • Hydrocarbons (e.g., methane, propane, butane)
  • Alcohol (e.g., ethanol, methanol)
  • Biomass (e.g., wood, peat, coal)

Let's take a closer look at a simple hydrocarbon combustion reaction using the example of methane (CH4):

CH4 + 2O2 → CO2 + 2H2O + Energy

In the above reaction, methane reacts with two molecules of oxygen to produce one molecule of carbon dioxide, two molecules of water and energy.

Changes in energy during combustion

Combustion reactions are exothermic. This means that they release more energy than they absorb. But how do we measure this energy change, and what does it tell us?

Enthalpy change (ΔH)

Enthalpy change, represented as ΔH, is an important concept in understanding energy transformations. It tells us how much heat energy is released or absorbed during a reaction at constant pressure. In combustion reactions, the enthalpy change is usually negative, indicating an exothermic process.

Let's look at an example:

CH4(g) + 2O2(g) → CO2(g) + 2H2O(l) ΔH = -890 kJ/mol

Here, ΔH is -890 kJ/mol, which means that 890 kilojoules of energy is released when each mole of methane is burned.

Activation energy

Activation energy is the minimum energy required to initiate a reaction. Even though combustion reactions are exothermic, they require a certain amount of energy to initiate. This energy is used to break the bonds of the reactants.

For example, when lighting a match, the friction produces enough activation energy to cause the match to burn.

Energy diagram

Energy diagrams can help show how energy changes during a combustion reaction.

Energy | ____ | / | | / | | _______________/ | |____________________________> Reaction Progress |__________| Activation Energy

In this simple energy diagram, we can see that the energy of the reactants is initially high due to activation energy. Once the reaction occurs, the energy is released, and the products are at a lower energy level.

Stoichiometry of combustion reactions

Understanding the stoichiometry of combustion reactions helps us calculate the amounts of reactants and products involved. Let's understand a simple example involving propane (C3H8):

C3H8 + 5O2 → 3CO2 + 4H2O

This balanced equation shows that 1 mole of propane reacts with 5 moles of oxygen to form 3 moles of carbon dioxide and 4 moles of water. Using stoichiometry, we can calculate how much oxygen is needed to completely burn a certain amount of propane.

Environmental impact of combustion

Combustion reactions are useful for producing energy, but they also have an impact on the environment. The combustion of fossil fuels releases carbon dioxide, a greenhouse gas that contributes to global warming. Additionally, incomplete combustion can produce carbon monoxide, a harmful pollutant.

It is important to adopt clean combustion technologies to reduce these environmental impacts. For example, catalytic converters in cars help reduce harmful emissions.

Conclusion

Understanding the energy transformations in combustion reactions is essential for both scientific knowledge and practical applications. Combustion reactions are vital for energy production, but they must be carefully managed to minimize harm to the environment. By understanding enthalpy, activation energy, and stoichiometry, we can better understand and improve combustion processes.


Grade 10 → 11.5


U
username
0%
completed in Grade 10

← Prev (11.4)
Specific heat capacity and calorimetry
Next (12) →
Electrochemistry

Comments 



Energy Changes in Combustion Reactions

https://www.chemistryelite.com/g10/11.5?ceal=en