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 → Plastics and polymers ↓


Biodegradable and Non-Biodegradable Plastics


Plastics are everywhere around us. They are used in products we use every day such as water bottles, toys, bags and more. However, not all plastics are the same. There are two main types of plastics based on their interaction with the environment: biodegradable and non-biodegradable plastics. In this explanation, we will explore what these terms mean and why they are important in our daily lives.

What is plastic?

Plastics are substances made of large molecules called polymers. These polymers are made of repeating units called monomers, which are small and simple molecules. The process of making plastics is called polymerization.

    Monomer (small molecule) + Monomer + Monomer → Polymer (large molecule)

A simple way to visualise this is to think of the polymer as a chain of beads, with each bead being a monomer.

Biodegradable plastic

Biodegradable plastics are designed to break down or decompose in the environment with the help of natural processes. These processes involve the actions of microorganisms such as bacteria, fungi, and algae. When biodegradable plastics decompose, they break down into natural substances such as carbon dioxide, water, and biomass.

Here's a simple visual example of what happens to biodegradable plastic:

    Biodegradable plastic + microbes → carbon dioxide + water + biomass

Biodegradable plastics are made from renewable resources such as plant materials including corn starch, potato starch, and sugar cane. They are beneficial because they help reduce plastic waste and pollution.

Features of biodegradable plastic

There are a few characteristics that make biodegradable plastics unique:

  • The main ingredients are often natural substances, such as plants.
  • They decompose naturally over time under specific conditions, such as heat, moisture, and the presence of microorganisms.
  • They help to minimise landfill waste and reduce pollution.

Non-biodegradable plastic

Non-biodegradable plastics are plastics that do not break down easily in the environment. They persist in nature for many years, possibly hundreds of years, before they begin to decompose. Unlike biodegradable plastics, non-biodegradable plastics are primarily made from petrochemicals, which are derived from fossil fuels.

A simple example of non-biodegradable plastic:

    Non-biodegradable plastic (resistant to microorganisms) → persists in the environment

Non-biodegradable plastics are strong, durable and inexpensive, making them ideal for many applications, but their sustainability is a major environmental problem as they accumulate and create waste.

Characteristics of non-biodegradable plastics

Typical characteristics of non-biodegradable plastics include:

  • They are made from petrochemicals derived from non-renewable resources.
  • They are durable, meaning they don’t break easily.
  • These take hundreds of years to decompose, causing long-term environmental problems.
  • They fill up landfills and contribute to marine pollution.

Difference between biodegradable and non-biodegradable plastic

Understanding the differences between these two types of plastic is important for making informed choices and promoting sustainability. Here are some of the key differences:

Aspect Biodegradable Plastic Non-biodegradable plastic
Composition Made from natural substances Made from petrochemicals
Putrefaction Break down naturally Last for hundreds of years
Environmental impact Reduced environmental hazards High environmental hazard
Raw material Renewable sources Non-renewable sources

Examples of biodegradable plastics

Here are some examples of biodegradable plastics:

  • Polylactic acid (PLA): Made from fermented plant starch derived from corn, cassava, sugar cane or beet pulp. Used in packaging, cups and compostable bags.
  • Polyhydroxyalkanoates (PHAs): Produced by microorganisms from sugars or lipids and used in medical applications and packaging.

Examples of non-biodegradable plastics

Some common non-biodegradable plastics include:

  • Polyethylene terephthalate (PET): Used in bottles and packaging.
  • Polyvinyl chloride (PVC): This is used in pipes, cables, and flooring.

Effects on environment and health

Non-biodegradable plastics are a serious concern for the environment and health. They contribute to pollution, harm wildlife and take up valuable space in landfills. Microplastics, which are tiny plastic particles, can be found in the oceans and pose a threat to marine life.

On the other hand, the use of biodegradable plastics, though a better option, must be managed properly. If not disposed of under proper conditions, they may not decompose effectively.

Closing thoughts

Understanding the difference between biodegradable and non-biodegradable plastic is the key to making informed choices that can help reduce environmental impacts. By choosing biodegradable plastic and reducing our reliance on non-biodegradable plastic, we can make a positive contribution to the ecosystem.


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