Grade 10
  1. Matter and its properties  1.1. States of matter  1.2. Physical and chemical properties of matter  1.3. Classification of substances (elements, compounds, mixtures)  1.4. Changes in Matter (Physical and Chemical Changes)  1.5. Law of conservation of mass and law of definite proportions
  2. Atomic Structure  2.1. Historical development of the atomic model  2.2. Subatomic particles (protons, neutrons, electrons)  2.3. Atomic number, mass number and isotopes  2.4. Electronic Configuration and Energy Levels  2.5. Valency, ion formation and oxidation state
  3. Periodic table  3.1. History and Development of the Periodic Table  3.2. Modern Periodic Law and Periodic Trends  3.3. Groups and Periods in the Periodic Table  3.4. Trends in the Periodic Table  3.5. Metals, non-metals, metalloids and their properties  3.6. Noble gases and their chemical inertness
  4. Chemical bond  4.1. Formation of Chemical Bonds (Octet Rule)  4.2. Ionic Bonding and Properties of Ionic Compounds  4.3. Covalent Bond and Properties of Covalent Compounds  4.4. Metallic bond and its properties  4.5. Molecular geometry and VSEPR theory  4.6. Polarity and dipole moment of molecules  4.7. Intermolecular forces
  5. Chemical Reactions and Equations  5.1. Types of Chemical Reactions  5.2. Writing and balancing chemical equations  5.3. Law of conservation of mass in chemical reactions  5.4. Factors Affecting Chemical Reactions  5.5. Catalysts and their role in chemical reactions  5.6. Exothermic and Endothermic Reactions
  6. Stoichiometry and Chemical Calculations  6.1. Mole concept and Avogadro number  6.2. Molar Mass and Gram-Mole Conversions  6.3. Empirical and molecular formula  6.4. Stoichiometric calculations and chemical yield  6.5. Limiting and Excess Reactants
  7. Acids, Bases and Salts  7.1. Properties and Definitions of Acids and Bases (Arrhenius, Bronsted-Lowry, Lewis)  7.2. pH Scale, pOH, and Indicators  7.3. Neutralization reactions and salt formation  7.4. Strength of Acids and Bases (Strong vs. Weak Acids and Bases)  7.5. Common Acids and Bases in Daily Life  7.6. Salts, their solubility and applications
  8. Metals and Nonmetals  8.1. Physical and chemical properties of metals  8.2. Physical and Chemical Properties of Non-Metals  8.3. Reactivity Series of Metals and Displacement Reactions  8.4. Extraction of metals from ores  8.5. Corrosion, its causes and prevention  8.6. Alloys, their composition and uses
  9. Carbon and its compounds  9.1. Allotropes of Carbon  9.2. Hydrocarbons and their classification (alkanes, alkenes, alkynes)  9.3. Functional groups in organic compounds  9.4. Nomenclature of organic compounds (IUPAC system)  9.5. Isomerism in organic chemistry (structural and geometrical)  9.6. Important organic reactions (combustion, addition, substitution, polymerization)  9.7. Applications of organic compounds in industry and daily life
  10. Environmental Chemistry  10.1. Air Pollution (Sources, Effects and Control)  10.2. Water Pollution (Causes, Effects and Remedies)  10.3. Greenhouse effect and global warming  10.4. Ozone layer depletion and its effects  10.5. Green Chemistry and Its Applications  10.6. sustainable chemistry practice
  11. Thermochemistry  11.1. Heat and Energy Changes in Chemical Reactions  11.2. Exothermic and Endothermic Reactions  11.3. Enthalpy, enthalpy change, and heat of reaction  11.4. Specific heat capacity and calorimetry  11.5. Energy Changes in Combustion Reactions
  12. Electrochemistry  12.1. Electrolytes and non-electrolytes  12.2. Electrolysis and its applications (electroplating, extraction of metals)  12.3. Redox reactions (oxidation and reduction)  12.4. Galvanic cell and electrochemical series  12.5. Corrosion and electrochemical prevention methods
  13. Chemical kinetics and equilibrium  13.1. Rate of chemical reactions and its measurement  13.2. Factors affecting the reaction rate (catalyst, temperature, concentration)  13.3. Reversible and irreversible reactions  13.4. Dynamic equilibrium and equilibrium constant  13.5. Le Chatelier's principle and its applications
  14. Gases and Gas Laws  14.1. Properties of gases and kinetic molecular theory  14.2. Boyle's Law (Pressure-Volume Relation)  14.3. Charles's Law  14.4. Gay-Lussac's Law  14.5. Combined Gas Law and Ideal Gas Law  14.6. Real Gases vs Ideal Gases
  15. Nuclear Chemistry  15.1. Introduction to Radioactivity and Nuclear Reactions  15.2. Types of radioactive decay (alpha, beta, gamma)  15.3. Half-life and applications of radioactive isotopes  15.4. Nuclear fission and fusion reactions  15.5. Nuclear power generation and its environmental impact

Grade 10 → Matter and its properties ↓


Changes in Matter (Physical and Chemical Changes)


Matter is everything that has mass and occupies space. It can undergo changes that are broadly classified into two categories: physical changes and chemical changes. Understanding these changes is fundamental in the study of the properties of matter and its interaction with energy.

Physical changes

A physical change in matter is a change in one or more of its physical properties, but not in its chemical composition. The identity of the matter does not change, and these changes are generally reversible. Changes in state, such as melting, boiling, freezing, and dissolving, are all examples of physical changes.

For example, when ice melts to become water, it undergoes a physical change. The substance is still H2O, but it goes from a solid state to a liquid state.

Visual example: change in water condition

Solid liquid Gas

Text example of physical changes

  • Melt: Ice melts into water.
  • Boiling: Water boiling into steam.
  • Freezing: The freezing of water into ice.
  • Dissolve: Sugar dissolves in water.

In all the above examples, the matter itself does not change chemically. No new matter is formed, which is why these are called physical changes.

Chemical changes

A chemical change occurs when a substance combines with another substance to form a new substance, called chemical synthesis, or alternatively, chemical decomposition into two or more separate substances. These processes are often difficult to reverse.

For example, when iron rusts, it reacts with oxygen to form iron oxide, a new chemical substance. This process is a chemical change because the chemical identity of the iron changes.

Visual example: rusting of iron

Fe + O2 Fe2O3

Text examples of chemical changes

  • Burning: Burning wood in a fire produces ash and releases gases such as carbon dioxide.
  • Rusting: Iron reacts with oxygen to form rust (Fe2O3).
  • Tarnishing: Silver reacts with sulfur in the air to form silver sulfide.
  • Cooking: Baking a cake causes the ingredients to react and form new substances.

All of these examples show a change where the resulting products are chemically different from the reactants, which indicates a chemical change.

Signs of a chemical change

Unlike physical changes, chemical changes bring about changes in the chemical composition of matter. Some common indicators of chemical change are as follows:

  • Colour change: When a substance takes on a new colour (e.g., iron rusting).
  • Gas emission: The emission of a gas, often seen as a bubble or odor (for example, vinegar reacting with baking soda).
  • Formation of a precipitate: A solid substance that forms from a solution during a chemical reaction (for example, mixing two clear solutions can sometimes yield a solid precipitate).
  • Change in temperature: Exothermic reactions release heat, while endothermic reactions absorb heat, causing a significant change in temperature (e.g., combustion releases heat).

Differentiating between physical and chemical changes

Sometimes it can be challenging to determine whether a change is physical or chemical. However, by examining certain characteristics, one can often distinguish between the two:

  • Reversibility:
    • Physical changes are usually reversible (e.g., freezing and melting of water).
    • Chemical changes are usually irreversible (e.g., cooking an egg).
  • Composition of the substance:
    • In physical changes the arrangement of molecules may change, but the structure remains the same (e.g., cutting wood).
    • In chemical changes, the structure of a substance is changed to form new substances (e.g., milk turning sour).

Observing energy changes, matter formation, or significant changes in properties can help identify the type of change.

The role of energy in the transformation of matter

Energy plays an important role in both physical and chemical changes. In physical changes such as melting or freezing, energy is used to change the state of matter. For example, when water freezes, it releases energy to become ice. Similarly, energy is absorbed during melting.

Energy and chemical reactions

Chemical changes often involve energy changes. There are two main types of energy changes in chemical reactions:

  • Exothermic reactions: Energy is released in the form of heat, which warms up the surroundings. Combustion of fuels is an example of this.
  • Endothermic reactions: absorb energy, usually as heat, causing the surroundings to cool. Photosynthesis in plants is an endothermic process.

The energy changes that accompany chemical reactions can be represented using thermochemical equations. These specify the heat terms involved. For example, the combustion of methane can be represented as follows:

CH4 + 2 O2 → CO2 + 2 H2O + energy

This equation states that burning methane in the presence of oxygen not only produces carbon dioxide and water, but also releases energy.

Applications and implications

Understanding physical and chemical changes is important in many real-world scenarios, from industrial processes to environmental systems. These principles are the basis of various technologies and affect our daily lives.

Industrial applications

Chemical changes are important in the industrial production of many products. For example, the Haber process synthesizes ammonia by combining nitrogen and hydrogen under specific temperature and pressure conditions:

N2 + 3 H2 ⇌ 2 NH3

Similarly, the refining of crude oil involves a number of chemical processes to produce fuels and other derivatives. Physical transformations are also important in materials management, such as melting metals for casting.

Environmental impact

Chemical changes can have both beneficial and harmful effects on the environment. For example, photosynthesis is vital for converting carbon dioxide into oxygen, which sustains life on Earth. In contrast, chemical pollutants can cause serious effects, such as acid rain and smog, which result from industrial emissions chemically reacting in the atmosphere.

Conclusion

Distinguishing between physical and chemical changes helps us understand the nature and properties of matter. Physical changes affect the form and state without altering the chemical composition, while chemical changes result in the formation of new substances. Recognizing these changes is essential for predicting outcomes in reactions, understanding natural systems, and applying this knowledge in technology and conservation efforts.


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Law of conservation of mass and law of definite proportions

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Changes in Matter (Physical and Chemical Changes)

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