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 ↓


Acids, Bases and Salts


Introduction

Chemistry is the study of matter and the changes that occur in it. One of the fundamental concepts in chemistry is the nature of acids, bases and salts. These substances are present everywhere in our daily lives, from the sourness of lemons to the soaps we use. This lesson will help you understand these concepts and their importance in simple terms.

What are acids?

Acids are substances that can donate protons or accept electron pairs in reactions. They have certain characteristics that make them unique. For example, acids have a sour taste, which you may have experienced when tasting vinegar or citrus fruits. Let's take a look at some of the unique properties of acids:

  • The taste of acid is sour.
  • They can conduct electricity when dissolved in water.
  • Acids turn blue litmus paper red.
  • They react with bases to form salt and water.

Common examples

Some common examples of acids include:

  • HCl
    Hydrochloric acid is found in stomach acid.
  • H2SO4
    Sulfuric acid, used in car batteries.
  • CH3COOH
    Acetic acid is found in vinegar.
  • H2CO3
    Carbonic acid is found in carbonated soda.

Visual representation of an acid molecule

H + CL -

What are the bases?

Bases are substances that can accept protons or donate electron pairs. They are often used in cleaning products because of their ability to react with grease and oil. Bases have different properties, including:

  • Bases taste bitter and are slippery.
  • They turn red litmus paper blue.
  • Bases can conduct electricity when dissolved in water.
  • They react with acids to form salt and water.

Common examples

Here are some typical bases you may encounter:

  • NaOH
    Sodium hydroxide is used in making soap.
  • NH3
    Ammonia is found in cleaning products.
  • Ca(OH)2
    Calcium hydroxide is used in plaster.
  • Al(OH)3
    Aluminum hydroxide is found in antacids.

Visual representation of a base molecule

Na + OH -

Acid-base reactions

When acids and bases react with each other, they neutralize each other. This reaction results in the formation of salt and water. This is called a neutralization reaction. For example:

HCl + NaOH → NaCl + H2O

In the above reaction, hydrochloric acid (

HCl
) reacts with sodium hydroxide (
NaOH
) to prepare sodium chloride (
sodium chloride
), commonly known as table salt, and water (
H2O
).

Visual representation of neutralization reaction

H + OH - H2O

What are salts?

Salts are ionic compounds formed by the neutralization reaction between an acid and a base. They are composed of positive ions (cations) and negative ions (anions). Some properties of salts are as follows:

  • Salts are generally solid at room temperature.
  • They can conduct electricity when dissolved in water.
  • Salt can have different tastes, such as salty or bitter.
  • They are often used in food, industry, and laboratories.

Common examples

Some common salts include:

  • sodium chloride
    Sodium chloride, which is used as table salt.
  • KNO3
    Potassium nitrate is used in fertilizers.
  • CaCO3
    Calcium carbonate is found in chalk and marble.
  • MgSO4
    Magnesium sulfate is used in Epsom salts.

Visual representation of a salt crystal

Na + CL -

PH scale

The pH scale measures how acidic or alkaline a solution is. It ranges from 0 to 14, with 7 being neutral. Solutions with a pH less than 7 are acidic, while solutions with a pH greater than 7 are alkaline.

  • pH 0-6: acidic solution
  • pH 7: neutral solution
  • pH 8-14: basic solution
Formula: pH = -log[H +]

Visual representation of the pH scale

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14

Brief review of acids, bases and salts

Throughout this lesson, we have explored the basic aspects of acids, bases, and salts in chemistry. Let's summarize what we learned:

  • Acids: Substances that donate protons and have a sour taste. Examples include hydrochloric acid and acetic acid.
  • Bases: Substances that accept protons, taste bitter and feel slippery. Examples include sodium hydroxide and ammonia.
  • Salts: Ionic compounds formed by an acid-base reaction. Examples include sodium chloride and calcium carbonate.
  • pH scale: Measures acidity or alkalinity, with 7 being neutral.

Practical applications of acids, bases and salts

Acids, bases, and salts are not just theoretical concepts; they have practical applications that significantly impact our daily lives. Here are some real-world examples that show their importance:

Applications of acids

  • Cleaning agents: Acidic products such as vinegar and lemon juice are effective for cleaning due to their ability to dissolve mineral deposits and grease.
  • Food additive: Citric acid is commonly found in soft drinks and other foods as a natural preservative and flavor enhancer.
  • Industrial uses: Sulfuric acid is important in the production of fertilizers, dyes, and batteries.

Applications of bases

  • Soaps and detergents: Sodium hydroxide is an important ingredient in soap making and various household cleaners.
  • Paper manufacturing: Bleach containing alkali is used to treat wood in the paper production process.
  • Antacids: Bases such as magnesium hydroxide are used to neutralize excess stomach acid and relieve indigestion.

Applications of salts

  • Taste of food: Sodium chloride is essential in cooking and preservation of food.
  • Ice melting on roads: Calcium chloride and sodium chloride are spread on icy roads in the winter to melt ice and increase safety.
  • Electrolyte balance: Salts are important in maintaining electrolyte balance in our body and are present in sports drinks.

Conclusion

Acids, bases, and salts are fundamental components of chemistry that have a significant impact on our world. Understanding their properties and how they interact helps us understand their role in everything from industry to daily household tasks. This exploration into their properties, reactions, and real-world applications reminds us of the important place chemistry has in life.


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