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 ↓


Properties of plastics


Introduction to plastics

Plastics are materials made from polymers, which are long chains of molecules. These chains give plastics their unique properties, making them very useful in everyday life. Plastics are found in countless items around us, from water bottles to toys and car parts. Understanding the properties of plastics can help us understand why they are used in so many products.

One of the main reasons plastics are so popular is that they can be made with different properties. For example, some plastics are soft and flexible, while others are hard and strong. Let's look at these properties in more detail.

Flexibility

One of the key properties of plastics is flexibility. Flexibility refers to the ability of a material to bend or twist without breaking. Some plastics, such as those used in plastic bags, are very flexible, allowing them to be bent easily.

To understand flexibility, imagine bending a rubber eraser. It can bend back and forth without breaking. This is similar to the behavior of flexible plastic.

Flexible movement

Strength

Another important property of plastics is strength. This means the ability to withstand force or pressure without breaking. Some plastics, such as those used in helmets or car bumpers, are designed to be very strong.

Think of a plastic ruler. It can withstand some pressure without breaking, which shows that it is relatively strong.

Strength under pressure

Tolerance

Durability refers to how long a material can last while performing its function. Plastics, in general, are very durable, meaning they can last a long time without breaking down.

Consider a plastic chair. It can withstand rain, sun, and normal use for many years, which shows its durability.

Plastic Chair

Lightweight

Another key characteristic of many plastics is that they are lightweight. Being lightweight makes them easy to carry and handle. This property is why plastics are often used in packaging and transportation.

Think of the plastic food containers you use at home. These are easy to carry around as they don't weigh much.

Lightweight and easy to carry

Water resistance

Most plastics do not absorb water, which is why they are used in products that need to be water resistant. Items like raincoats and waterproof bags are often made from plastics that repel water.

Imagine a plastic rain boot lying in a puddle; it keeps your feet dry because water doesn't get into them.

Waterproof Boots

Chemical composition

The properties of plastics depend largely on their chemical structure. Plastics are made of polymers, which are substances composed of large molecules with repeating structural units.

The repeating units in a polymer are known as monomers. Imagine these monomers as links in a chain. When these links join, they form a polymer chain.

Monomer: -CC- Polymer: -CCCCC-

Types of plastic

Plastics can be divided into two primary types based on their chemical and physical properties: thermoplastics and thermosetting plastics.

Thermoplastics

Thermoplastics are plastics that soften when heated and harden when cooled. This process can be repeated many times, allowing thermoplastics to be reshaped and recycled.

Common examples of thermoplastics include polyethylene used in plastic bags and polypropylene used in packaging.

Heating: softens Cooling: hardens

Thermosetting plastics

Thermosetting plastics are materials that, once hardened, cannot be reshaped by heating or recycled. They are set in a permanent shape.

Examples include Bakelite, which is used in electrical switches, and melamine, which is used in kitchen utensils.

Once set: remains solid (no reshaping)

Environmental impact

Plastic has many useful properties, but it also has an impact on the environment. Plastic is very durable, so it does not break down easily, leading to problems with waste and pollution.

Reducing plastic waste by recycling or using alternative materials can help reduce this impact. Reusing plastic products instead of throwing them away can also make a difference.

For example, instead of throwing away plastic bags after using them once, you can use cloth bags that can be used many times.

Recycling symbol

Conductivity

Plastics are generally poor conductors of electricity, making them excellent insulators. This is why plastics are often used to protect electrical wires and components from electrical shock.

Imagine electrical wires wrapped in plastic: this covering acts as an insulator against electricity.

Electrical Insulation

Thermal properties

Plastics also have thermal properties, including how they react to heat. While some plastics can melt when heated, others can withstand high temperatures. This property is essential when using plastics in kitchen appliances or industrial settings.

For example, silicone, a type of plastic, can tolerate heat and is used in baking molds.

Heat resistant bakeware

Aesthetic qualities

Plastics have versatile aesthetic properties, due to which they can be made in a variety of colors and finishes. This makes them suitable for designing attractive products.

Consider a colorful phone case. It is not only functional but also complements personal stylistic preferences.

Colorful Phone Case

Conclusion

Understanding the properties of plastics helps us understand why they are integral to so many aspects of life. From flexibility and strength to being lightweight and durable, the properties of plastics allow them to be formulated into countless shapes for different uses.

Furthermore, the environmental implications of plastic highlight the importance of responsible use and recycling. As technology advances, we continue to find new ways to use plastic in an environmentally sustainable way.

Plastics play a vital role in modern society, combining versatility with practicality. Their wide range of properties truly demonstrates how scientific innovations can impact our daily lives.


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Natural and synthetic polymers
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Biodegradable and Non-Biodegradable Plastics

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Properties of plastics

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