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


In this exploration of air and atmosphere, we will learn about the composition, properties, and importance of air and atmosphere. We will also understand the scientific principles that explain how air behaves, and we will explore its importance to life on Earth.

What is air?

Air is an invisible, odorless and tasteless mixture of gases that surrounds our planet. It is essential for most life forms on Earth, as it provides oxygen for animals and plants. Air is mainly composed of:

  • Nitrogen (N 2) - about 78%
  • Oxygen (O 2) - about 21%
  • Argon (Ar) - about 0.93%
  • Carbon dioxide (CO 2) - about 0.04%
  • The rest is made up of other trace gases and water vapor
78% Nitrogen 21% oxygen

Components of air and their roles

Let us delve deeper into the main components of air and understand their roles:

Nitrogen (N 2)

Nitrogen is the most abundant gas in the air. Although it does not directly support life through respiration like oxygen, it is important in other ways. Nitrogen is a major component of DNA, proteins, and other biological molecules. It is also essential for the production of fertilizers in the agricultural industry, as plants need nitrogen to grow.

Oxygen (O 2)

Oxygen is essential for respiration in most living organisms. During respiration, cells use oxygen to convert glucose into energy, water, and carbon dioxide, a process called cellular respiration. Here's a simplified illustration of this process:

C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O + energy

Carbon dioxide (CO 2)

Carbon dioxide is used by plants to make glucose and oxygen during photosynthesis. This process is essential for plant growth and the survival of many ecosystems. The chemical equation for photosynthesis is:

6CO 2 + 6H 2 O + light energy → C 6 H 12 O 6 + 6O 2

An interesting fact is that carbon dioxide is very important for plants, but humans and animals excrete it as a waste product.

Argon

Argon is a noble gas and is chemically inert. It does not contribute much to chemical processes in the atmosphere, but it is used in light bulbs and welding to provide an inert atmosphere.

Composition of the atmosphere

The atmosphere is made up of several layers, each of which has its own characteristics. Let's learn about these layers:

  1. Troposphere: This is the lowest layer, where we live. It extends about 8 to 15 kilometers above the earth. Weather phenomena like rain, snow and storms occur in the troposphere.
  2. Stratosphere: Located above the troposphere, it extends up to about 50 kilometers. The ozone layer, which protects us from the sun's harmful UV radiation, resides in the stratosphere.
  3. Mesosphere: Extending from about 50 to 85 kilometers, this layer is where meteors often burn up upon entry.
  4. Thermosphere: This layer extends from about 85 to 600 kilometers. The temperature increases with altitude and aurora phenomenon occurs here.
  5. Exosphere: The outermost layer of the atmosphere extends more than 600 kilometers and gradually disappears into outer space.
Layers of the atmosphere Exosphere Thermosphere Mesosphere Stratosphere Troposphere

Importance of the atmosphere

The Earth's atmosphere plays a vital role in sustaining life and providing a suitable environment for survival. Some of the major roles of the atmosphere are as follows:

  • Protection from harmful radiation: The ozone layer in the stratosphere absorbs and scatters solar ultraviolet radiation, providing protection to living organisms from harmful effects.
  • Climate regulation: The atmosphere helps regulate the Earth's temperature by trapping heat from the Sun, a phenomenon known as the greenhouse effect.
  • Physical protection: Thick layers of the atmosphere burn up meteoroids that would otherwise fall to the Earth's surface.
  • Air to breathe: The atmosphere provides gases necessary for respiration and other life processes.

Human impact on the atmosphere

Human activities have significant impacts on the atmosphere, both locally and globally. These include:

Air pollution

Air pollution is caused by the release of harmful substances into the air, which can be natural or man-made. Common pollutants include:

  • Carbon monoxide (CO): It is a colourless, odourless gas produced by the incomplete combustion of carbon-containing substances.
  • Nitrogen oxides (NO x): These are produced by vehicle emissions and contribute to smog and acid rain.
  • Sulfur dioxide (SO 2): This is emitted mainly from the combustion of fossil fuels in power plants and industrial facilities, contributing to acid rain.
  • Particulate matter (PM): Fine particles that can harm respiratory health.

Greenhouse gases

Greenhouse gases trap heat in the atmosphere and contribute to global warming. Important greenhouse gases include:

  • Carbon dioxide (CO 2): Emitted through activities such as burning fossil fuels (coal, oil, natural gas), deforestation, and land use changes.
  • Methane (CH 4): Emitted from the production and transportation of coal, oil, and natural gas, as well as from livestock and other agricultural practices.
  • Water vapor: While part of the natural water cycle, increases in water vapor due to global warming can increase the greenhouse effect.

Efforts towards better air quality

Many steps have been taken and international agreements have been made to reduce the adverse effects of air pollution and global warming, including:

Clean Air Act

Governments around the world have implemented environmental regulations to limit emissions of pollutants, thereby improving air quality.

International protocols and agreements

Global efforts such as the Kyoto Protocol and the Paris Agreement aim to reduce greenhouse gas emissions and address climate change by setting targets for countries.

Renewable energy sources

Adopting alternative energy sources such as solar, wind and hydropower helps reduce dependence on fossil fuels, thereby reducing carbon emissions.

The future of air and atmosphere

Understanding air and the atmosphere is vital to developing strategies to tackle climate change and ensure a healthy planet for future generations. Continuous education and innovation are needed to address the challenges posed by atmospheric changes and pollution.

We have discussed in detail the composition, role and importance of air and atmosphere. We have also explored the impacts of human activities and efforts to counter these impacts. A comprehensive understanding of air and atmospheric science is vital to maintaining air quality and sustaining life on Earth.


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Air and atmosphere

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