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 → Matter and its properties → States of matter ↓


Solid state


The solid state is one of the fundamental states of matter, along with liquid, gas, and plasma. Molecules in the solid state are tightly bound to each other, which means they have a definite shape and volume. To better understand this concept, let's learn what makes the solid state unique and how it differs from other states of matter.

What is the definition of solid?

Solids have a definite shape and volume because the molecules that make up solids are very closely packed together and do not move around freely. Unlike liquids and gases, solids do not conform to the shape of their container. Instead, they maintain their own shape.

Concrete examples

In the diagram above, each colored square represents a solid object. Notice how each square maintains its distinct shape and doesn't change no matter where they are placed.

Particle arrangement in solids

The particles (atoms or molecules) in a solid are arranged in a regular pattern, often forming crystals. The particles vibrate but do not move from their fixed positions, which contributes to the stiffness of solids. Here's a simplified illustration of what this looks like:

Particle arrangement in solids

The particles are so closely packed that their motion is restricted to tiny vibrations. This orderly arrangement prevents solids from being easily compressed.

Types of solids

Solids can be classified into two main types: crystalline and amorphous solids.

Crystalline solid

Crystalline solids have well-defined geometric shapes due to their organized structure. They have a clear melting point, which is the temperature at which they change from solid to liquid.

Examples of crystalline solids include:

  • Salt (NaCl)
  • Diamond (a form of carbon)
  • Sugar (C12H22O11)

Amorphous solid

Amorphous solids lack a definite shape and melt over a range of temperatures rather than having a sharp melting point. They have a more random arrangement of particles.

Examples of amorphous solids include:

  • Glass
  • Plastic
  • Jail

Properties of solids

Solids have a number of characteristic properties:

  • Definite shape and volume: Unlike gases and liquids, solids have a definite shape and volume.
  • Incompressibility: Solids cannot be compressed easily because their particles are close to each other.
  • Higher density: Solids are generally denser than liquids and gases, meaning they have more mass per unit volume.
  • Rigidity: Solids retain their shape even when subjected to external forces.

Examples and applications of solids

Solids are essential in our everyday lives and have numerous applications:

Household items

Many items in your home are solid, such as:

  • Furniture such as tables and chairs
  • Kitchen utensils such as plates and cutlery
  • Electronics like computers and phones

Building materials

Solids are important in construction:

  • Bricks and concrete used for buildings
  • Steel is used for structural support
  • Lumber used in residential construction

Everyday tools

The tools we use for various tasks are often solid:

  • Hammer
  • Screwdriver
  • Saw

The role of scientists

Scientists continue to study solids to improve technology and materials. They engage in activities such as creating stronger materials or finding new uses for existing materials. Understanding the basic properties of solids helps develop new applications.

Important terms

Here are some important terms related to the solid state:

  • Lattice: The ordered, repetitive arrangement of atoms or molecules in a crystal.
  • Melting point: The temperature at which a solid changes into a liquid.
  • Density: A measure of how much mass is contained in a given volume.

Conclusion

The solid state is a fundamental aspect of matter that has unique properties that make solids invaluable in everyday life. Their hardness, shape, and volume are characteristics that distinguish them from liquids and gases. Understanding how solids work helps us understand their role in the world around us and informs scientific and technological advancements.


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States of matter
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Solid state

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