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 → Acids, Bases and Salts ↓


Strong and weak acids and bases


In this detailed explanation, we will dive into the world of strong and weak acids and bases. Acids and bases are substances we often encounter in our everyday lives. They can be found in household items, foods, and even our own bodies. Let's learn why some acids and bases are strong, while others are considered weak.

What are acids and bases?

First, let's define what acids and bases are. These substances are part of a broad category of chemicals that have specific properties. Acids are substances that are sour tasting, turn blue litmus paper red and release hydrogen ions (H +) in water. Bases, on the other hand, are bitter tasting, slippery, turn red litmus paper blue and release hydroxide ions (OH -) in water.

Acid: HCl → H + + Cl -
Base: NaOH → Na + + OH -

Everyday examples include lemon juice (acidic) and baking soda (alkaline).

Strong acid and weak acid

Strong acids

Strong acids are those that completely dissociate in water. This means that almost all of the molecules in a strong acid break down into ions. Because of this complete dissociation, strong acids are very good at conducting electricity and are more reactive.

Some common examples of strong acids include:

  • HCl (hydrochloric acid)
  • HNO3 (nitric acid)
  • H2SO4 (sulfuric acid)

Visual explanations

HCl H + CL -

As shown above, HCl dissociates completely into H + and Cl - ions.

Weak acid

Weak acids do not completely dissociate into ions in water. Instead, only a small portion of the weak acid molecules dissociate. Thus, they are less effective at conducting electricity and are generally less reactive.

Examples of weak acids include:

  • CH3COOH (acetic acid)
  • H2CO3 (carbonic acid)
  • H3PO4 (phosphoric acid)

Visual explanations

CH 3 COOH H + CH 3 COO -

In the case of acetic acid, only a few molecules dissociate into H + and CH3COO-.

Strong base and weak base

Strong base

Strong bases, like strong acids, dissociate completely in water, forming large quantities of hydroxide ions. They are good conductors of electricity and are very reactive.

Common examples include:

  • NaOH (sodium hydroxide)
  • KOH (potassium hydroxide)
  • Ca(OH)2 (calcium hydroxide)

Visual explanations

NaOH Na + Oh -

The above illustration shows NaOH splitting into Na + and OH -.

Weak base

Weak bases only partially dissociate in water. They produce fewer hydroxide ions, which makes them poor conductors of electricity.

Examples of weak bases are:

  • NH3 (ammonia)
  • C5H5N (pyridine)

Visual explanations

NH 3 NH4 + Oh -

As illustrated, NH3 is partially dissociated in water into NH4 + and OH - ions.

Importance of pH in strong and weak acids and bases

The pH scale helps us understand the strength of acids and bases. The scale ranges from 0 to 14. A pH less than 7 indicates an acid, while a pH greater than 7 indicates a base. A pH of 7 is neutral, as in pure water.

  • Strong acids have a pH value close to 0 (for example, HCl can have a pH value around 1).
  • Weak acids have a pH value close to 7 (for example, CH3COOH can have a pH value of 4-5).
  • Strong bases have a pH value close to 14 (for example, NaOH can have a pH value around 13).
  • Weak bases have a pH value close to 7 (for example, NH3 can have a pH value of 9-11).

Applications of strong and weak acids and bases

Acids and bases have a wide range of uses in the real world, from industrial processes to everyday household uses.

Strong acids

  • Hydrochloric acid (HCl): Used in processing steel and in the production of chlorides and fertilizers.
  • Sulfuric acid (H2SO4): Commonly used in car batteries and chemical manufacturing.

Weak acids

  • Acetic acid (CH3COOH): Found in vinegar and used as a food preservative.
  • Carbonic acid (H2CO3): This is formed in carbonated drinks when CO2 dissolves in water.

Strong bases

  • Sodium hydroxide (NaOH): Used in making soap and drain cleaners.
  • Potassium hydroxide (KOH): Used in cosmetics and as an electrolyte in batteries.

Weak bases

  • Ammonia (NH3): Used as a cleaning agent and a precursor to fertilizers.

Conclusion

Understanding the difference between strong and weak acids and bases helps us understand their diverse applications and impact on everyday life. Strong acids and bases dissociate completely in water, while weak acids and bases do not. This difference plays an important role in their behavior, use, and the safety measures required when handling them.

Knowledge about pH and dissociation is essential in many scientific fields and industrial applications. Using this understanding, we can use acids and bases safely and effectively in a variety of scenarios, making them invaluable in our daily lives.


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Strong and weak acids and bases

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