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 ↓


Introduction to Chemical Formulas


Understanding the elements

Everything around us is made up of elements. An element is a pure substance that cannot be broken down into simpler forms. Each element is made up of only one kind of atom. For example, oxygen is an element. Every atom in a container of oxygen gas is identical.

Each element has a unique chemical symbol, usually one or two letters. For example:

  • Hydrogen: H
  • Oxygen: O
  • Carbon: C

Visual example of elements

He

This circle with "He" represents a helium atom, which is an example of an element.

Understanding compounds

When two or more elements combine, they form a compound. The properties of a compound are different from the properties of the elements that make it up. Water is a good example of a compound. It is made up of two hydrogen atoms and one oxygen atom. When they combine, a completely different substance is formed: water.

Chemical formulas tell how many of each type of atom are in a compound. The chemical formula for water is H 2 O. This means it has two hydrogen atoms (H 2) and one oxygen atom (O).

Visual example of compound

H H O

The above picture shows a water molecule, which has two hydrogen atoms and one oxygen atom.

Understanding mixtures

Mixtures are different from compounds. The substances in a mixture are combined physically, not chemically. This means that each substance in the mixture has its own properties. An example of a mixture is a salad. You can still see and taste each individual ingredient such as lettuce, tomatoes, and cucumbers. They do not change chemically and can be easily separated.

Mixtures can be homogeneous or heterogeneous. In a homogeneous mixture, the composition is completely uniform, such as salt dissolved in water. In a heterogeneous mixture, the composition is not uniform, such as a salad.

Examples of mixtures

1. Salad - lettuce, tomato, and cucumber
2. Sand and water
3. Air - mixture of nitrogen, oxygen, and other gases

As shown, each component in a mixture retains its individual properties.

Chemical formula in compounds

Chemical formulas show the type and number of atoms in a compound. For example:

  • CO 2: Carbon dioxide - 1 carbon atom, 2 oxygen atoms
  • C 6 H 12 O 6: Glucose - 6 carbon atoms, 12 hydrogen atoms, 6 oxygen atoms

Visual representation of chemical formulas

C O2 C H 12 O 6

Here, CO 2 represents one molecule of carbon dioxide and C 6 H 12 O 6 represents one molecule of glucose.

How to write a chemical formula

Writing a chemical formula involves identifying the elements involved and using the correct sub-digits to indicate the number of each type of atom:

  • Step 1: Find the chemical symbols of the elements.
  • Step 2: Determine the number of each type of atom present.
  • Step 3: Write the chemical formula using the symbols and any sub-digits as needed.

Practice writing formulas

1. Magnesium Chloride - Magnesium (Mg), Chloride (Cl) Formula: MgCl 2
2. Sodium Bicarbonate - Sodium (Na), Hydrogen (H), Carbon (C), Oxygen (O) Formula: NaHCO 3

Practice helps you remember to write chemical formulas correctly.

Conclusion

Knowing how to read and write chemical formulas is vital to understanding chemistry. Elements, compounds, and mixtures form the basis of chemical formulas, each of which has its own distinct properties and combinations. Using simple rules, you can determine the composition of different substances. Remember, practicing and understanding these concepts lays the foundation for studying more advanced topics in chemistry.


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Introduction to Chemical Formulas

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