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 → Elements, Compounds, and Mixtures ↓


Definition of Compound


In the fascinating world of chemistry, we often talk about elements, compounds, and mixtures. These are fundamental concepts that help us understand the substances around us. The purpose of this article is to focus on compounds: what they are, how they differ from elements and mixtures, and why they are important in science and everyday life.

Understanding compounds

A compound is a substance that is formed when two or more chemical elements are chemically bonded together. The elements in a compound are present in fixed proportions, and these proportions do not change. When elements form compounds, they lose their individual properties and form a substance with new properties.

Element A Element B deeply concerned Mixture

The diagram above shows how two elements, A and B, can combine to form compounds. Let's look at some of the main characteristics of compounds.

Characteristics of compounds

  • Compounds have a fixed structure. This means that the ratio of elements in the compound is always the same. For example, the chemical formula of water is H 2 O, which means that it always has two hydrogen atoms for every oxygen atom.
  • Compounds exhibit properties different from the elements they are made from. For example, sodium is a reactive metal, and chlorine is a poisonous gas. When they form a compound, they create table salt (NaCl), which is safe to eat.
  • Compounds can only be separated into their elements by chemical means. This is different from mixtures, which can be separated by physical methods.

To understand compounds further, let's look at some common examples.

Examples of compounds

Water

One of the best-known compounds is water. Water is composed of two hydrogen atoms bonded to one oxygen atom, forming the chemical formula H 2 O. Hydrogen is a flammable gas and oxygen supports combustion, yet water is a liquid essential to life.

2H 2 + O 2 → 2H 2 O

This chemical equation shows how two molecules of hydrogen gas react with one molecule of oxygen gas to form two molecules of water.

Carbon dioxide

Carbon dioxide is another common compound, essential for life on Earth. Plants use carbon dioxide to make oxygen in photosynthesis. It is composed of one carbon atom bonded to two oxygen atoms, giving it the formula CO2.

C + O 2 → CO 2

The reaction above shows how carbon and oxygen combine to form carbon dioxide, an important compound in the Earth's atmosphere.

Sodium chloride (Table salt)

Sodium chloride, better known as table salt, is another example of a compound. It forms when sodium and chlorine chemically bond together. The resulting formula is NaCl. The properties of sodium chloride are very different from those of sodium or chlorine alone.

Na + Cl → NaCl

This formula shows how sodium reacts with chlorine to form sodium chloride, a compound essential in everyday life for flavoring and preserving food.

Difference between compounds and mixtures

In chemistry, it is important to understand the difference between compounds and mixtures. Although both contain two or more components, there is a great difference in their formation and properties.

Compounds

  • Compounds are chemically linked together, and the elements form a specific ratio.
  • They have new properties different from their constituent elements.
  • Separation into individual elements requires chemical methods.

Mixture

  • Mixtures are not chemically bonded, and the components retain their individual properties.
  • The composition of mixtures can vary and is not as stable as compounds.
  • Separation of the components is possible through physical means, such as filtration or evaporation.

For example, salad is a mixture. You can physically separate the lettuce from the tomatoes, and each component has its own taste and appearance. In contrast, a compound such as carbon dioxide requires a chemical reaction to separate the carbon and oxygen atoms.

Importance of compounds in daily life

Compounds play important roles in our daily lives and exist in different forms:

  • Medicines: Many medicines are compounds that are designed to interact with the human body to treat diseases. For example, aspirin (C 9 H 8 O 4) is a compound used to relieve pain and reduce inflammation.
  • Cooking: Various compounds in food contribute to the flavor, aroma, and nutritional value. Sodium bicarbonate (NaHCO 3), also known as baking soda, is a compound used in baking.
  • Cleaning: Many cleaning products contain compounds that help remove dirt and kill germs. For example, bleach usually contains sodium hypochlorite (NaClO), a compound effective at sanitizing surfaces.

Compounds are incredibly diverse and include synthetic materials such as plastics (polymers) and natural substances such as proteins and carbohydrates. They are central to scientific research, technological advancement and the development of new materials and medicines.

Chemical bonds in compounds

The atoms in a compound are held together by chemical bonds, which can be covalent, ionic, or metallic. Each bond type has unique properties that affect the characteristics of the compound.

Covalent bonds

In covalent bonds, atoms share electrons to achieve stability. An example of this is water (H 2 O), where hydrogen and oxygen share electrons.

Ionic bond

Ionic bonds form when one atom donates electrons to another, creating charged ions. Sodium chloride (NaCl) is an ionic compound where sodium donates electrons to chlorine.

Metal bond

Although less common in simple compounds, metallic bonding involves a 'sea of electrons' shared between metal atoms, providing conductivity and strength. An example of this is alloys such as steel.

Conclusion

Understanding compounds is fundamental to understanding the chemistry of the world around us. Compounds are unique substances that have properties that differ from their constituent elements, formed through different types of chemical bonds. They are important for many applications in daily life, from healthcare to industry.

As we continue to discover and explore new compounds, our understanding of chemical processes deepens, opening the door to innovations that can improve and enrich human life. The study of compounds not only enriches our knowledge but also fuels the continuous pursuit of scientific and technological advancements.


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Definition of Compound

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