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 ↓


Chemical reactions


Introduction

Chemistry is the study of matter and its changes. In our everyday lives, chemical reactions happen all the time. These reactions can be as simple as adding salt to water or as complex as the reactions that produce heat and light in the sun.

What is a chemical reaction?

A chemical reaction is a process in which substances, called reactants, are transformed into different substances, called products. During a chemical reaction, the atoms in the reactants rearrange themselves to form new chemical bonds, forming products.

For example, when hydrogen gas reacts with oxygen gas, water is formed. The equation for this reaction is:

2H 2 + O 2 → 2H 2 O

Visual example:

H2 H2 O2 responds to form H2O H2O

Types of chemical reactions

There are many types of chemical reactions, but here are some of the most common:

1. Synthesis reactions

In a synthesis reaction, two or more reactants combine to form a new, single product. An example of a synthesis reaction is the formation of water from hydrogen and oxygen:

2H 2 + O 2 → 2H 2 O

2. Decomposition reactions

In a decomposition reaction, a single compound breaks down into two or more simpler products. For example, when water is decomposed by electricity, it forms hydrogen and oxygen gases:

2H 2 O → 2H 2 + O 2

3. Single replacement reactions

In a single replacement reaction, one element in a compound replaces another element. An example of this type of reaction is when zinc reacts with hydrochloric acid to form zinc chloride and hydrogen gas:

Zn + 2HCl → ZnCl 2 + H 2

4. Double replacement reactions

In a double replacement reaction, the ions of two compounds swap places in an aqueous solution to form two new compounds. For example, when silver nitrate reacts with sodium chloride, silver chloride and sodium nitrate are formed:

AgNO 3 + NaCl → AgCl + NaNO 3

5. Combustion reactions

In combustion reactions, matter reacts rapidly with oxygen to produce energy in the form of heat and light. A simple example is the burning of methane gas:

CH 4 + 2O 2 → CO 2 + 2H 2 O

States of matter in reactions

In chemical equations, the physical states of the reactants and products are often indicated. Common states are:

  • (s) for solid
  • (l) for liquid
  • (g) for gas
  • (aq) for aqueous, meaning dissolved in water

For example, the reaction between solid sodium and water is expressed as:

2Na(s) + 2H 2 O(l) → 2NaOH(aq) + H 2 (g)

Balancing chemical equations

In chemistry, it is important to balance chemical equations. This means that the number of atoms of each element in the reactant side should be equal to the number of atoms in the product side. Let us understand how to balance a chemical equation using the combustion of methane step by step:

CH 4 + O 2 → CO 2 + H 2 O

Step 1: Count the atoms of the elements on both sides.

Reactants: 1 Carbon (C), 4 Hydrogen (H), 2 Oxygen (O). Products: 1 Carbon (C), 2 Hydrogen (H), 3 Oxygen (O).

Step 2: Balance the hydrogen atoms by adding a coefficient of 2 before H 2 O :

CH 4 + O 2 → CO 2 + 2H 2 O

Step 3: Balance the oxygen atoms by placing a coefficient of 2 next to O 2 :

CH 4 + 2O 2 → CO 2 + 2H 2 O

The equation is now balanced!

Factors affecting chemical reactions

Several factors can affect the rate and outcome of chemical reactions:

1. Temperature

Increasing the temperature generally increases the rate of the reaction. This is because the particles move more quickly and collide more frequently and more energetically.

2. Concentration

Higher concentrations of reactants can cause collisions to occur more frequently, resulting in a more intense reaction.

3. Surface area

Finely divided substances or reactants with a large surface area react faster, because more particles are available to react.

4. Catalyst

Catalysts are substances that speed up a reaction without being consumed in the process. They work by lowering the activation energy required for the reaction to take place.

Importance of chemical reactions in daily life

Chemical reactions are fundamental to many processes in our daily lives. They are involved in cooking, cleaning, breathing, and even driving a car. Understanding these reactions helps us make informed decisions about product use and technology.

Conclusion

Chemical reactions are the backbone of chemistry. They transform substances in millions of ways, providing the basis for understanding the nature and structure of the matter around us. Through chemical reactions, we can harness energy, create new materials, and understand complex biological processes. By studying them, we gain insight into the workings of the universe at a fundamental level.


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