Grade 8
  1. Introduction to Chemistry  1.1. Nature and scope of chemistry  1.2. Importance of chemistry in daily life  1.3. Chemistry and its relation with other sciences  1.4. The role of chemistry in industry, medicine and the environment  1.5. Scientific investigation and experimental methods in chemistry
  2. Matter and its properties  2.1. Definition and classification of matter  2.2. Physical and chemical properties of matter  2.3. Law of conservation of matter  2.4. Extensive and Intensive Properties of Matter  2.5. Kinetic molecular theory of matter  2.6. States of matter: solids, liquids, gases, plasmas, and Bose-Einstein condensates  2.7. Changes in state and energy are involved  2.8. Diffusion and Brownian motion
  3. Elements, Compounds, and Mixtures  3.1. Definition and differences between elements, compounds, and mixtures  3.2. Atomic Structure and Atomic Number  3.3. Chemical symbols and formulas  3.4. Trends in the Periodic Table (Groups and Periods)  3.5. Classification of Elements: Metals, Nonmetals and Metalloids  3.6. Rare Earth Elements and Transition Metals  3.7. Types of mixtures: homogeneous and heterogeneous  3.8. Separation of Mixtures Using Physical and Chemical Methods
  4. Separation Techniques  4.1. Filtration, Sedimentation and Decantation  4.2. Evaporation and crystallization  4.3. Distillation and Fractional Distillation  4.4. Chromatography and its applications  4.5. Sublimation in the purification of compounds  4.6. The role of centrifugation in biochemical processes
  5. Atomic Structure  5.1. Dalton's atomic theory  5.2. Structure of the atom: protons, neutrons and electrons  5.3. Bohr's atomic model  5.4. Introduction to Quantum Mechanical Model  5.5. Electron Configuration and Energy Levels  5.6. Excitation and emission spectra  5.7. Isotopes and their applications
  6. Periodic Table and Chemical Trends  6.1. History and Development of the Periodic Table  6.2. Modern periodic law  6.3. Periodicity and trends in atomic and ionic sizes  6.4. Ionization Energy, Electron Affinity and Electronegativity  6.5. Introduction to Lanthanides and Actinides  6.6. Application of periodic trends in chemistry
  7. Chemical Bonding and Molecular Structure  7.1. Types of chemical bonds: ionic, covalent and metallic bonds  7.3. Polar and Nonpolar Molecules  7.4. Hydrogen bonding and its applications  7.5. Intermolecular forces: dipole-dipole, London dispersion force
  8. Chemical Reactions and Stoichiometry  8.1. Chemical Equations and Balance  8.2. Types of Chemical Reactions: Combination, Decomposition, Displacement and Redox  8.3. Introduction to stoichiometry and the mole concept  8.4. Limiting reactant in chemical equations  8.5. Reaction rate, catalyst, and factors affecting reaction rate
  9. Acids, Bases and Salts  9.1. Definition and Properties of Acids and Bases  9.2. Strong vs. Weak Acids and Bases  9.3. pH Scale and pH Calculation  9.4. Neutralization reactions  9.5. Buffer solutions and their importance  9.6. Applications of Acids, Bases and Salts in Daily Life
  10. Solutions and Solubility  10.1. Definition of Solution, Solute, and Solvent  10.2. Factors Affecting Solubility  10.3. Concentration units: molarity and molality  10.4. Saturated, unsaturated and supersaturated solutions  10.5. Concept of osmosis and reverse osmosis  10.6. Concentrative properties of solutions
  11. Gases and Gas Laws  11.1. Properties of gases  11.2. Introduction to Ideal and Real Gases  11.3. Boyle's Law, Charles' Law and Avogadro's Law  11.4. Ideal Gas Equation and Its Applications  11.5. Application of Gas Laws in Real Life
  12. Thermochemistry and energy transformation  12.1. Energy in Chemical Reactions  12.2. Exothermic vs. Endothermic Reactions  12.3. Heat and Enthalpy Changes  12.4. Calorimetry and heat transfer in reactions
  13. Metals and Nonmetals  13.1. Physical and Chemical Properties of Metals and Nonmetals  13.2. Reactivity Series of Metals  13.3. Corrosion and its prevention  13.4. Extraction of metals from ores  13.5. Uses of metals and non-metals in daily life
  14. Introduction to Organic Chemistry  14.1. Characteristics of carbon and organic compounds  14.2. Functional groups and their importance  14.3. Simple Hydrocarbons: Alkenes, Alkenes and Alkynes  14.4. Isomerism in organic compounds  14.5. Introduction to polymers and their uses
  15. Environmental Chemistry and Sustainability  15.1. Green Chemistry Principles  15.2. Effects of Chemical Pollution on Ecosystems  15.3. Acid rain and its effects  15.4. Ozone layer depletion and global warming  15.5. Waste Management and Recycling in Chemistry

Grade 8 ↓


Elements, Compounds, and Mixtures


Let's explore the fascinating world of chemistry by understanding three important concepts: elements, compounds, and mixtures. These are the basic building blocks of everything around us. We'll discuss each topic in depth using simple language and provide plenty of examples to help you understand these fundamental ideas.

Elements

Elements are pure substances that contain only one type of atom. Each element is unique and is represented by a chemical symbol in the periodic table. For example, the symbol for oxygen is O, and for hydrogen it is H

  ,
  | H | He | Li |
  ,
  | h | b | c |
  ,
  | N | O | F |
  ,

Consider the element gold. It is always made of gold atoms and nothing else. No matter where you find gold, its basic structure remains the same.

In total, there are 118 known elements, and they form the basis of all matter. Some elements, such as oxygen (O), are essential for life, while others, such as helium (He), are used in balloons because they are less dense than air.

Compounds

Compounds are substances that are formed when two or more elements join together chemically. When elements combine to form compounds, they lose their individual properties, and the compound formed has its own unique characteristics.

For example, water is a compound made up of two hydrogen atoms and one oxygen atom. Its chemical formula is H 2 O

  H + O →
  ,
   
  ,
 yes

In the case of water, hydrogen and oxygen are gases, but when they combine, they become liquids at room temperature. This shows that the properties of compounds can be quite different from the properties of the elements that make them up.

Another example of a compound is table salt, which has the chemical formula NaCl. It is composed of sodium, a reactive metal, and chlorine, a poisonous gas. Together, they form a stable and essential substance for life.

Mixture

A mixture is a combination of two or more substances where each substance retains its own properties. Unlike compounds, the components of a mixture are not chemically bonded. Instead, they are physically mixed, which means they can be separated by physical methods.

Consider a mixture of sand and iron filings. The two substances retain their individual properties, and you can use a magnet to easily separate the iron filings from the sand.

  Sand + Fe →
  ,
  ,

Mixtures can be homogeneous or heterogeneous. In homogeneous mixtures, the composition is the same throughout, such as salt dissolved in water. In contrast, heterogeneous mixtures have different components, such as a salad with lettuce, tomatoes, and cucumbers.

Difference between elements, compounds and mixtures

Let us summarize the differences between elements, compounds and mixtures in simple terms:

  • Elements: Pure substances containing only one type of atom. They cannot be broken down into simpler substances. Example: oxygen (O).
  • Compounds: Pure substances formed by chemical bonding of two or more elements. Can be broken down into simpler substances by chemical means. Example: water (H 2 O).
  • Mixture: Combination of different substances that are not chemically bonded. Can be separated by physical means. Example: A mixture of sand and water.

How do they exist in nature

In nature, elements can be found either as individual atoms or combined together in different forms. For example, oxygen can be found in the air as O 2, which is a molecule made up of two oxygen atoms.

Compounds are found in abundance in nature and make up everything from the tiniest bacteria to the vast oceans. For example, our bodies contain many compounds essential for life, such as proteins and carbohydrates.

Mixtures are also abundant in nature. Seawater is a mixture of water, salt, and various other minerals. The atmosphere is a mixture of gases, mainly nitrogen and oxygen, with trace amounts of other gases.

The importance of understanding these concepts

Understanding elements, compounds and mixtures is important in a variety of fields, including science, medicine, engineering and environmental studies. It helps us understand how different substances interact and react with each other, allowing us to develop new materials, medicines and technologies.

For example, by understanding how elements combine to form compounds, chemists can create new medicines to treat diseases. Environmental scientists study the mixture of gases in the atmosphere to understand climate change.

Conclusion

Elements, compounds and mixtures are the backbone of chemistry and the physical world around us. Elements are the basic building blocks, while compounds are formed by the chemical bonding of these elements. Mixtures are more complex combinations that retain their individual properties. By learning about these fundamental concepts, we gain a broad understanding of the nature of matter and the universe.


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