Grade 6
  1. Introduction to Chemistry  1.1. What is Chemistry?  1.2. Importance of chemistry in daily life  1.3. Branches of chemistry  1.4. Safety rules in chemistry laboratory  1.5. Common Laboratory Equipment and Their Uses
  2. Matter and its states  2.1. Definition of Matter  2.2. Properties of matter  2.3. States of matter  2.4. Solid state  2.5. Fluid state  2.6. Gaseous state  2.7. Plasma state  2.8. Changes in the states of matter  2.9. Melting and freezing  2.10. Evaporation and Condensation  2.11. Sublimation  2.12. Deposit
  3. Physical and chemical changes  3.1. Definition of Physical Change  3.2. Examples of physical change  3.3. Definition of Chemical Change  3.4. Examples of chemical change  3.5. Difference Between Physical and Chemical Changes  3.6. Indicators of Chemical Change
  4. Elements, Compounds, and Mixtures  4.1. Definition of the element  4.2. Classification of elements  4.3. Metals  4.4. Non metallic  4.5. Metalloids  4.6. Noble gases  4.7. Definition of compound  4.8. Properties of Compounds  4.9. Definition of Mixture  4.10. Types of mixtures  4.11. Homogeneous mixture  4.12. Heterogeneous mixtures
  5. Separation of mixtures  5.1. The need for isolation  5.2. Separation methods  5.3. Handpicking and winnowing  5.4. Filtration  5.5. Sedimentation and decantation  5.6. Evaporation  5.7. Crystallization  5.8. Distillation  5.9. Magnetic Separation  5.10. Chromatography
  6. Air and its composition  6.1. Components of air  6.2. Importance of Oxygen  6.3. The importance of nitrogen in the air and its composition  6.4. Carbon dioxide in the atmosphere  6.5. The role of water vapor and other gases in air and its composition  6.6. Properties of Air  6.7. Uses of air  6.8. Air pollution and its effects
  7. Water and its properties  7.1. Importance of Water  7.2. Sources of water  7.3. Properties of water  7.4. Water as the universal solvent  7.5. Water Purification  7.6. Water purification methods (boiling, filtration, chlorination)  7.7. Water cycle  7.8. Water conservation  7.9. Water pollution and its effects
  8. Acids, Bases and Salts  8.1. Definition of Acid  8.2. Properties of Acids  8.3. Examples of Acids  8.4. Definition of Bases  8.5. Properties of bases  8.6. Examples of Bases  8.7. Definition of Salt  8.8. Neutralization reaction  8.9. pH Scale and Indicators  8.10. Uses of Acids, Bases and Salts
  9. Introduction to the Periodic Table  9.1. History of the Periodic Table  9.2. Arrangement of elements in the periodic table  9.3. Groups and periods  9.4. Importance of periodic table  9.5. First 10 elements and their symbols
  10. Metals and Nonmetals  10.1. Properties of Metals  10.2. Properties of Non-Metals  10.3. Difference Between Metals and Nonmetals  10.4. Uses of metals and nonmetals  10.5. Corrosion of metals and its prevention
  11. chemical reactions  11.1. Introduction to Chemical Reactions  11.2. Types of Chemical Reactions  11.3. combustion reaction  11.4. Oxidation and Reduction  11.5. Simple chemical equations  11.6. Rusting of iron
  12. Fuel and energy  12.1. Types of fuel  12.2. Fossil fuels  12.3. Renewable and non-renewable sources of energy  12.4. Energy Conservation  12.5. Alternative sources of energy (solar, wind, hydropower)
  13. Plastic and fiber  13.1. Natural and synthetic fibers  13.2. Properties of plastics  13.3. Advantages and disadvantages of plastic  13.4. Recycling of plastic  13.5. Biodegradable and non-biodegradable materials

Grade 6 ↓


Physical and chemical changes


In our everyday life, we see many changes happening around us. Some of these changes may be big, like a forest fire, while some may be small, like sugar dissolving in tea. To understand these changes better, scientists classify them as physical or chemical changes. Let us learn about these two types of changes in detail.

What are the physical changes?

A physical change is a change in one or more physical properties of a substance, without any change in its chemical composition. Physical changes are usually reversible. During a physical change, the appearance, shape, or phase of the matter may change, but no new substance is formed.

Examples of physical change

Below are some common examples of physical changes taking place around us:

  • Melting of ice: When ice melts, it turns into water. The shape and state change, but the chemical composition remains H 2 O.
  • Boiling water: When water boils, it becomes steam. Here the change is from liquid to gas.
  • Glass breakage: When glass breaks its shape changes, but the glass particles remain the same.
  • Cutting paper: When you cut a sheet of paper into smaller pieces, its size and shape change, but chemically it remains the same.

Visual example: melting ice

snow Water Heat

What are chemical changes?

A chemical change results in the formation of one or more new substances. This type of change alters the chemical structure of the matter involved, meaning that the atoms in the substance are rearranged to form new products. Chemical changes are usually not reversible by simple physical means.

Examples of chemical change

Here are some examples of chemical changes:

  • Burning wood: When wood burns, it combines with oxygen to form ash, carbon dioxide, and water vapor. This chemical reaction is irreversible.
  • Baking a cake: When a cake is baked, ingredients such as eggs, flour, and baking powder undergo a chemical change, forming a new product: a cake.
  • Rusting of Iron: When iron rusts, it reacts with oxygen and water to form a new compound, iron oxide (rust).
  • Digestion of food: In the digestive system, chemical changes are carried out to convert food into nutrients and waste products.

Visual example: rusty iron

Iron War Oxidation

Difference between physical and chemical changes

To summarize, the main differences between physical and chemical changes are as follows:

Physical changes Chemical change
No new substance is formed. A new substance is formed.
The changes are usually reversible. The changes are usually irreversible.
Only the physical properties change. Chemical properties also change.
Energy changes may be temporary or minor. Changes in energy can be significant.

Reversible and irreversible changes

Some changes can be both physical and reversible. For example, when water freezes or melts, it can be returned to its original state by heating or cooling it. Chemical changes, on the other hand, are irreversible, meaning that once a new substance is formed, it cannot easily return to its original components without another chemical reaction.

Conclusion

In conclusion, understanding the difference between physical and chemical changes helps us understand how different processes work in nature and the materials we interact with every day. Identifying whether a process is physical or chemical can help us predict whether it can be reversed and what kind of energy or products might be involved.


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Physical and chemical changes

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