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 → Air and atmosphere ↓


Importance of Oxygen and Carbon Dioxide


Air is a mixture of gases that surrounds the Earth and is essential for life. One of the primary components of air is oxygen, and another important component is carbon dioxide. Both gases play a vital role in the environment and in various chemical processes that sustain life.

Understanding the composition of air

Air contains about 78% nitrogen, 21% oxygen and about 0.03% carbon dioxide. The remaining percentage consists of other gases and water vapor. Let's take a look at these gases and find out the important roles of oxygen and carbon dioxide.

Oxygen: The essential breath of life

Oxygen is a colorless, odorless gas that makes up about 21% of the Earth's atmosphere. It is essential for the survival of most living organisms. Oxygen is required for the respiratory process that takes place in all living cells.

Respiration

Respiration is the process by which cells obtain energy. In this, energy is produced by breaking down glucose with the help of oxygen. This energy is required for various cellular functions. The chemical equation for this process is:

C6H12O6 + 6O2 → 6CO2 + 6H2O + energy

This shows that glucose (C6H12O6) combines with oxygen (O2) to form carbon dioxide (CO2), water (H2O) and energy. This energy is used by the cells to perform their functions.

Visual example: Respiratory process

Oxygen (O2) sugar CO2 H2O

Other uses of oxygen

Oxygen is also used in a variety of industrial processes, such as steelmaking, welding, and the manufacture of chemicals such as ammonia and methanol. Additionally, it is important for medical treatments where patients require additional oxygen, such as anesthesia or respiratory disorders.

Carbon dioxide: A vital gas for life and climate

Carbon dioxide is a colorless gas that is present in very small quantities in the atmosphere. Despite its low concentration, it has a significant impact on life and environmental processes.

Photosynthesis

Plants produce glucose and oxygen using carbon dioxide in the process of photosynthesis. This process is important for providing energy to plants and releasing oxygen into the atmosphere for animals and humans to breathe. The chemical formula for photosynthesis is:

6CO2 + 6H2O + sunlight → C6H12O6 + 6O2

This equation shows how plants take in carbon dioxide and water, and make glucose and oxygen using sunlight. Photosynthesis is the foundation of food chains in ecosystems.

Visual example: Photosynthesis

CO2 H2O Sun sugar O2

Effects on climate

Carbon dioxide is a greenhouse gas, meaning it traps heat in the Earth's atmosphere and contributes to the greenhouse effect. It's important for keeping the planet warm enough to sustain life, but increasing carbon dioxide levels can lead to climate change.

Carbon dioxide in the oceans

The oceans absorb a significant amount of carbon dioxide from the atmosphere. This helps maintain balance in the global carbon cycle, but it can also lead to acidification of the oceans, affecting marine life.

Equation for dissolving carbon dioxide in water
CO2 (g) + H2O (l) → H2CO3 (aq)

When carbon dioxide dissolves in water, it forms carbonic acid — a weak acid that affects the pH of the water.

Industrial and domestic use

Carbon dioxide is used in a variety of applications, such as the carbonation of soft drinks, as a refrigerant in the form of dry ice, and in fire extinguishers.

Balance of oxygen and carbon dioxide

The balance between oxygen and carbon dioxide in the atmosphere is very important. Oxygen supports life processes through respiration, while carbon dioxide provides the raw material necessary for photosynthesis, closing the cycle and sustaining life on Earth.

Human activities and their impact

Human activities such as industrialization, deforestation, and the burning of fossil fuels can upset this delicate balance, increasing carbon dioxide levels, which contributes to global warming and climate change.

Measures and protection

Efforts to reduce carbon emissions, conserve energy and promote reforestation are essential to maintain the balance of these gases and protect the environment.

Closing thoughts

Oxygen and carbon dioxide are fundamental gases that are vital for life on Earth. Understanding their role and maintaining their balance is important for the environment and future generations.


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Properties of gases in the air
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Importance of Oxygen and Carbon Dioxide

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