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 → Metals and Nonmetals ↓


Reactivity Series of Metals


The reactivity series of metals is a list of metals arranged in order of decreasing reactivity. The most reactive metal is placed at the top and the least reactive metal at the bottom. Understanding this series helps in explaining and predicting the behaviour of the metal in displacement reactions, its method of extraction and its reactions with water and acids.

Understanding the reactivity series

Reactivity in metals refers to how easily the metal loses its electrons to form positive ions. Metals at the top of the reactivity series, such as potassium (K) and sodium (Na), are highly reactive. They react rapidly with water and oxygen, forming compounds such as KOH (potassium hydroxide) and Na 2 O (sodium oxide).

        K + H2O → KOH + H2

This reaction shows that potassium reacts with water to form potassium hydroxide and hydrogen gas.

Order of reactivity

Metals are listed in order from most reactive to least reactive. Here is a simplified list showing the reactivity series:

  • Potassium (K)
  • Sodium (Na)
  • Calcium (Ca)
  • Magnesium (Mg)
  • Aluminum (Al)
  • Zinc (Zn)
  • Iron (Fe)
  • Lead (Pb)
  • Copper (Cu)
  • Silver (Ag)
  • Gold (Au)
  • Platinum (Pt)

In the SVG example, imagine two metal blocks, one representing potassium and the other gold. The potassium block is reacting vigorously with the water, producing bubbles of hydrogen gas, while the gold block is stationary and not reacting with the water.

Potassium Gold

Reactivity and displacement reactions

Displacement reactions occur when a more reactive metal can displace a less reactive metal from its compound. For example, when magnesium is added to a solution of copper sulfate, magnesium will displace copper because magnesium is more reactive:

        Mg + CuSO4 → MgSO4 + Cu

In this reaction magnesium sulphate and copper metal are formed. This type of displacement helps in separating metals during extraction.

Reaction with water

Reactive metals such as sodium and potassium react vigorously with water to form hydrogen gas and metal hydroxides. For the most reactive metals this reaction can be explosive. Here's how sodium reacts with water:

        2Na + 2H 2 O → 2NaOH + H 2

Metals lower in the reactivity series, such as iron or copper, do not react with water in the same way.

Reaction with acids

Most metals react with acids to form hydrogen gas and salts. Reactivity depends on the position of the metal in the reactivity series. Here is an example of zinc reacting with hydrochloric acid:

        2HCl + Zn → ZnCl2 + H2

Gold and platinum, being at the bottom of the reactivity series, do not react with acids.

Metal removal

The reactivity of a metal determines how it is extracted from its ore. For example, highly reactive metals such as sodium and aluminum are extracted using electrolysis, while less reactive metals such as zinc and iron are extracted by reduction with carbon.

In extraction by electrolysis, metal ions at the electrodes are reduced to form the pure metal. For example, extracting aluminum from aluminum oxide:

        2Al 2 O 3 → 4Al + 3O 2

Visualizing the series

Imagine a ladder with metals arranged from the most reactive to the least reactive metal at the top. At the top, you'll find metals that are very reactive and challenging to find as free metals in nature, and at the bottom, you'll find metals like gold, which are often found in their native form.

K Na Ca Mg

This visualization helps illustrate how metals at different reactivity levels might "stand" relative to one another on our reactivity ladder.

Industrial applications

Knowledge of the reactivity series is important in many industrial applications. For example, the galvanization process, where a protective zinc layer is applied to iron or steel to prevent corrosion, involves less reactive iron being displaced by more reactive zinc. Another application is in sacrificial protection, where a more reactive metal such as magnesium is used to protect a less reactive metal such as iron from corrosion.

Chemical vs. physical properties

It is important to distinguish between chemical reactivity and physical properties. For example, the shiny appearance of a metal (a physical property) does not necessarily indicate high reactivity (a chemical property).

Summary

The reactivity series of metals is a valuable tool in chemistry that helps explain a variety of reactions and processes. Knowing the series allows students and scientists to predict the outcomes of reactions, understand extraction methods, and apply this knowledge in practical applications such as the prevention of metal corrosion.


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Physical and Chemical Properties of Metals and Nonmetals
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Corrosion and its prevention

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Reactivity Series of Metals

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