Grade 9
  1. Matter and its nature  1.1. Introduction to matter  1.2. Physical and chemical properties of matter  1.3. States of matter  1.3.1. Solid state  1.3.2. Fluid state  1.3.3. Gaseous state  1.3.4. Plasma and Bose–Einstein condensate  1.4. Changes in the states of matter  1.4.1. Melting and freezing  1.4.2. Evaporation and Condensation  1.4.3. Sublimation and deposition  1.5. Classification of matter  1.6. Elements, Compounds, and Mixtures  1.7. Pure substances and impurities  1.8. Separation Techniques  1.8.1. Filtration  1.8.2. Distillation  1.8.3. Crystallization  1.8.4. Chromatography  1.8.5. Centrifugation  1.8.6. Sublimation  1.8.7. Decantation and sedimentation
  2. Atomic Structure  2.1. Discovery of atoms  2.2. Dalton's atomic theory  2.3. Structure of the atom  2.4. Subatomic particles  2.5. Atomic number and mass number  2.6. Isotopes and Isobars  2.7. Electronic configuration  2.8. Bohr's atomic model  2.9. Modern Atomic Model (Quantum Mechanical Model - Introduction)  2.10. Valency and chemical bonding
  3. C hemical reactions and equations  3.1. Introduction to Chemical Reactions  3.2. Chemical Equation Formulation  3.3. Balancing Chemical Equations  3.4. Types of Chemical Reactions  3.4.1. Combination Reactions  3.4.2. Decomposition reactions  3.4.3. Displacement reactions  3.4.4. Double displacement reactions  3.4.5. Redox reactions  3.4.6. Endothermic and Exothermic Reactions  3.5. Effects of chemical reactions  3.6. Energy Changes in Chemical Reactions  3.7. Catalysts and their role in reactions
  4. Periodic table and periodicity  4.1. History of Periodic Classification  4.2. Mendeleev's periodic table  4.3. Modern Periodic Table  4.4. Periods and groups in the periodic table and periodicity  4.5. Trends in the Periodic Table  4.5.1. Atomic size  4.5.2. Ionization Energy  4.5.3. Electron affinity  4.5.4. Electronegativity  4.5.5. Metallic and Non-Metallic Properties  4.6. Noble gases and their properties
  5. Chemical bond  5.1. Introduction to Chemical Bonding  5.2. Types of chemical bonds  5.2.1. Ionic bond  5.2.2. Covalent bond  5.2.3. Metallic bond  5.2.4. Hydrogen bonding  5.2.5. Van der Waals force  5.3. Properties of Ionic and Covalent Compounds  5.4. Molecular Structure and Geometry (VSEPR Theory - Basics)
  6. Acids, Bases and Salts  6.1. Introduction to Acids and Bases  6.2. Properties of Acids  6.3. Properties of bases  6.4. pH scale and its importance  6.5. Indicators and their uses  6.6. Neutralization reactions  6.7. Strength of Acids and Bases (Strong vs. Weak)  6.8. Preparation of salts  6.9. Uses of acids, bases and salts in daily life
  7. Metals and Nonmetals  7.1. Physical Properties of Metals  7.2. Physical Properties of Nonmetals  7.3. Chemical properties of metals  7.4. Chemical Properties of Nonmetals  7.5. Reactivity Series of Metals  7.6. Extraction of metals  7.7. Corrosion and its prevention  7.8. uses of metals and nonmetals
  8. Carbon and its compounds  8.1. Introduction to Carbon  8.2. Allotropes of carbon (diamond, graphite, fullerene)  8.3. Hydrocarbons  8.3.1. Hydrocarbons  8.3.2. Alkene  8.3.3. Alkynes  8.4. Functional groups in organic chemistry  8.5. Isomerism in organic compounds  8.6. Alcohols and Carboxylic Acids  8.7. Soaps and detergents  8.8. Polymers (Introduction to Natural and Synthetic Polymers)
  9. Solutions and Mixtures  9.1. Types of mixtures  9.2. Homogeneous and Heterogeneous Mixtures  9.3. Concentration of solutions  9.4. Solubility and factors affecting solubility  9.5. Suspensions and Colloids  9.6. Saturated, unsaturated and supersaturated solutions
  10. Air and atmosphere  10.1. Composition of air  10.2. Role of gases in the atmosphere  10.4. Acid rain and its effects  10.5. Greenhouse effect and global warming  10.6. Ozone layer and its depletion  10.7. Air pollution control measures
  11. Water and its importance  11.1. Composition and properties of water  11.2. Hardness of water (temporary and permanent hardness)  11.3. Causes of water pollution  11.4. Effects of Water Pollution  11.5. Water purification methods (filtration, boiling, chlorination)
  12. Industrial Chemistry  12.1. Introduction to Industrial Chemistry  12.2. Important industrial chemicals (sulfuric acid, ammonia, sodium hydroxide)  12.3. Chemical processes in industry  12.4. Uses of Industrial Chemistry in Daily Life  12.5. Environmental impact of industrial chemical processes

Grade 9 → Acids, Bases and Salts ↓


Properties of bases


Bases are an important class of chemical substances. They play a key role in various chemical reactions and have many applications in everyday life. In chemistry, understanding the properties of bases helps us identify and use them efficiently. In this explanation, we will explore the various properties of bases in detail, providing examples and simple explanations to make the concept easier to understand.

What are the bases?

Bases are chemicals that can accept hydrogen ions ( H + ) or, more commonly, donate a pair of valence electrons. They are usually identified by certain properties such as taste, feel, and their reactions with indicators and acids.

Physical properties of bases

Taste

Bases often taste bitter. This is one reason why foods such as baking soda and unsweetened chocolate (which contains bases) taste bitter. However, taste testing unknown substances in a laboratory is unsafe and should be avoided.

Feel

Bases can feel slippery or soapy to the touch. This is because they react with lipids in the skin to form soap-like compounds. An example of this is the slippery feeling of soap, which contains a basic substance called sodium hydroxide.

Example: When you wash your hands with soap, you may feel slippery. This is because soap contains a base that combines with the oils on your skin to form a soap-like compound, causing a slippery feeling.

Chemical properties of bases

Reaction with acids (neutralization)

Bases react with acids in a process called neutralization. This reaction forms salt and water. The general form of a neutralization reaction is:

Acid + Base → Salt + Water

For example, when hydrochloric acid ( HCl ) reacts with sodium hydroxide ( NaOH ), the products are sodium chloride ( NaCl ), a salt, and water ( H 2 O ):

HCl + NaOH → NaCl + H 2 O

Reacting with indicators

Bases change the colour of certain dyes called indicators. Indicators are substances that change colour when added to acidic or alkaline solutions. Some common indicators and their colour changes in the presence of bases are as follows:

  • Litmus Paper: Under basic conditions, blue litmus paper stays blue while red litmus paper turns blue.
  • Phenolphthalein: It turns pink in the presence of alkali.
  • Bromothymol Blue: It turns blue under basic conditions.

Example: If you dip red litmus paper in sodium hydroxide solution it will turn blue, which indicates that the solution is alkaline.

Electrolytic nature

Bases are electrolytes, which means they can conduct electricity when dissolved in water. This happens because bases dissociate into ions, which are charged particles capable of carrying an electric current. This property makes them suitable for use in electrolytic cells and batteries.

Example: A solution of potassium hydroxide ( KOH ) in water can conduct electricity because KOH dissociates into its component ions ( K + and OH - ), making it possible for electrical charge to flow.

Alkalinity

Bases have a high pH level, usually greater than 7. The pH scale ranges from 0 to 14, with 7 being neutral. Solutions with a pH greater than 7 are alkaline or basic. The higher the pH, the more basic the solution.

Example: A solution of ammonia ( NH 3 ) in water may have a pH of about 11, indicating that it is an alkaline solution.

Common examples of bases

There are many common ground that you may encounter in everyday life. Here are some examples:

  • Sodium hydroxide ( NaOH ): Commonly known as caustic soda or lye, used in soap making.
  • Potassium hydroxide ( KOH ): Sometimes used to make liquid soap and as a fertilizer.
  • Ammonia ( NH 3 ): Used in household cleaning products.
  • Calcium hydroxide ( Ca(OH) 2 ): Known as slaked lime, it is used in construction and making cement.
  • Magnesium hydroxide ( Mg(OH) 2 ): Known as milk of magnesia, used as an antacid.

Sodium hydroxide ( NaOH )

Sodium Hydroxide - NaOH

Sodium hydroxide or NaOH is one of the most common bases. It is used to make soap and paper and in chemical laboratories. It reacts easily with acids and is one of the strongest bases available.

Ammonia ( NH 3 )

Ammonia - NH 3

Ammonia is a gas at room temperature and is commonly used in household cleaners. It is less corrosive than sodium hydroxide and has a distinctive, pungent odor. It can also be found in fertilizers due to its high nitrogen content.

Applications of bases

Bases have numerous applications in different fields, which is why they are essential in daily life.

In the industry

  • Soap and detergent manufacturing: Sodium hydroxide is used to make soap. Potassium hydroxide is used in the production of liquid soap.
  • Paper manufacturing: Sodium hydroxide is used in the paper industry to pulp wood and refine paper products.
  • Textile industry: Alkalis help dye fabrics and improve color fastness.
  • Food industry: Ammonium hydroxide is used as a pH control agent in food processing.

In medicine

  • Antacids: Magnesium hydroxide and calcium carbonate are used to neutralise stomach acid and relieve heartburn.
  • Cleaning agents: Many bases are used in antiseptic products and cleaning agents to kill germs and remove dirt.

Safety precautions with bases

Despite their beneficial uses, alkalis can be corrosive and dangerous if not handled properly. It is important to follow certain safety measures when working with alkalis.

Guidelines for safe operation

  • Wear protective equipment such as gloves and goggles when working on strong bases.
  • Use the base in a well-ventilated area to avoid fumes.
  • In case of skin contact, wash area immediately with plenty of water.
  • To prevent accidental reactions, store bases in labeled, appropriate containers away from acids.

By understanding and respecting the properties of bases, we can use them effectively while ensuring safety. This comprehensive overview of the properties and applications of bases provides information about their importance in both scientific and practical contexts.


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Properties of bases

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