Grade 9
  1. Matter and its nature  1.1. Introduction to matter  1.2. Physical and chemical properties of matter  1.3. States of matter  1.3.1. Solid state  1.3.2. Fluid state  1.3.3. Gaseous state  1.3.4. Plasma and Bose–Einstein condensate  1.4. Changes in the states of matter  1.4.1. Melting and freezing  1.4.2. Evaporation and Condensation  1.4.3. Sublimation and deposition  1.5. Classification of matter  1.6. Elements, Compounds, and Mixtures  1.7. Pure substances and impurities  1.8. Separation Techniques  1.8.1. Filtration  1.8.2. Distillation  1.8.3. Crystallization  1.8.4. Chromatography  1.8.5. Centrifugation  1.8.6. Sublimation  1.8.7. Decantation and sedimentation
  2. Atomic Structure  2.1. Discovery of atoms  2.2. Dalton's atomic theory  2.3. Structure of the atom  2.4. Subatomic particles  2.5. Atomic number and mass number  2.6. Isotopes and Isobars  2.7. Electronic configuration  2.8. Bohr's atomic model  2.9. Modern Atomic Model (Quantum Mechanical Model - Introduction)  2.10. Valency and chemical bonding
  3. C hemical reactions and equations  3.1. Introduction to Chemical Reactions  3.2. Chemical Equation Formulation  3.3. Balancing Chemical Equations  3.4. Types of Chemical Reactions  3.4.1. Combination Reactions  3.4.2. Decomposition reactions  3.4.3. Displacement reactions  3.4.4. Double displacement reactions  3.4.5. Redox reactions  3.4.6. Endothermic and Exothermic Reactions  3.5. Effects of chemical reactions  3.6. Energy Changes in Chemical Reactions  3.7. Catalysts and their role in reactions
  4. Periodic table and periodicity  4.1. History of Periodic Classification  4.2. Mendeleev's periodic table  4.3. Modern Periodic Table  4.4. Periods and groups in the periodic table and periodicity  4.5. Trends in the Periodic Table  4.5.1. Atomic size  4.5.2. Ionization Energy  4.5.3. Electron affinity  4.5.4. Electronegativity  4.5.5. Metallic and Non-Metallic Properties  4.6. Noble gases and their properties
  5. Chemical bond  5.1. Introduction to Chemical Bonding  5.2. Types of chemical bonds  5.2.1. Ionic bond  5.2.2. Covalent bond  5.2.3. Metallic bond  5.2.4. Hydrogen bonding  5.2.5. Van der Waals force  5.3. Properties of Ionic and Covalent Compounds  5.4. Molecular Structure and Geometry (VSEPR Theory - Basics)
  6. Acids, Bases and Salts  6.1. Introduction to Acids and Bases  6.2. Properties of Acids  6.3. Properties of bases  6.4. pH scale and its importance  6.5. Indicators and their uses  6.6. Neutralization reactions  6.7. Strength of Acids and Bases (Strong vs. Weak)  6.8. Preparation of salts  6.9. Uses of acids, bases and salts in daily life
  7. Metals and Nonmetals  7.1. Physical Properties of Metals  7.2. Physical Properties of Nonmetals  7.3. Chemical properties of metals  7.4. Chemical Properties of Nonmetals  7.5. Reactivity Series of Metals  7.6. Extraction of metals  7.7. Corrosion and its prevention  7.8. uses of metals and nonmetals
  8. Carbon and its compounds  8.1. Introduction to Carbon  8.2. Allotropes of carbon (diamond, graphite, fullerene)  8.3. Hydrocarbons  8.3.1. Hydrocarbons  8.3.2. Alkene  8.3.3. Alkynes  8.4. Functional groups in organic chemistry  8.5. Isomerism in organic compounds  8.6. Alcohols and Carboxylic Acids  8.7. Soaps and detergents  8.8. Polymers (Introduction to Natural and Synthetic Polymers)
  9. Solutions and Mixtures  9.1. Types of mixtures  9.2. Homogeneous and Heterogeneous Mixtures  9.3. Concentration of solutions  9.4. Solubility and factors affecting solubility  9.5. Suspensions and Colloids  9.6. Saturated, unsaturated and supersaturated solutions
  10. Air and atmosphere  10.1. Composition of air  10.2. Role of gases in the atmosphere  10.4. Acid rain and its effects  10.5. Greenhouse effect and global warming  10.6. Ozone layer and its depletion  10.7. Air pollution control measures
  11. Water and its importance  11.1. Composition and properties of water  11.2. Hardness of water (temporary and permanent hardness)  11.3. Causes of water pollution  11.4. Effects of Water Pollution  11.5. Water purification methods (filtration, boiling, chlorination)
  12. Industrial Chemistry  12.1. Introduction to Industrial Chemistry  12.2. Important industrial chemicals (sulfuric acid, ammonia, sodium hydroxide)  12.3. Chemical processes in industry  12.4. Uses of Industrial Chemistry in Daily Life  12.5. Environmental impact of industrial chemical processes

Grade 9 → Matter and its nature → States of matter ↓


Solid state


When we think of matter, we usually think of the things around us such as air, water, trees, rocks, and countless other objects. Matter is anything that has mass and occupies space, and it exists in different states – primarily solid, liquid, and gas. In this discussion, we are going to focus on the solid state of matter and explore its characteristics, properties, and how it differs from other states of matter.

What is solid?

A solid is a state of matter that has structural rigidity and resistance to changes in shape or volume. Unlike liquids, a solid object does not flow to take the shape of its container, nor does it expand to fill the entire volume available to it like a gas. Instead, solids maintain a definite shape and volume. This is because the particles in a solid are very closely packed together and arranged in a definite structure.

Visual example of a solid object

Imagine marbles packed tightly in a box. When you shake the box, the marbles may move a little, but their arrangement does not change. This is similar to the arrangement of particles in a solid.

Properties of solid matter

Solids have the following characteristics:

  • Definite shape and volume: Solids have a definite shape and volume. This means that they do not need a container to maintain their shape, which persists as long as physical conditions such as temperature and pressure remain constant.
  • Incompressibility: Solids are generally incompressible because of the dense packing of their molecules.
  • High density: Solids usually have higher densities than liquids and gases because the arrangement of their atoms or molecules is much denser. The exception to this is ice, which is less dense than liquid water.
  • Low diffusion: The particles in solids do not move freely; hence, diffusion in solids is very low compared to liquids and gases.
  • Rigidity: Solids are rigid and resist external forces to change their shape. This rigidity is due to the strong forces of attraction between their particles.

Understanding atomic structure in solids

To understand why solids have these properties, we need to deeply understand their atomic structure. In solids, atoms or molecules are arranged in a certain order that determines the properties of the matter. Let's explore these arrangements.

Crystalline solid

In crystalline solids, atoms, ions, or molecules are arranged in an ordered three-dimensional pattern over long distances. This regular pattern is called a crystal lattice. Examples of crystalline solids include salt, sugar, and metals such as iron and copper.

Visual example of a crystalline solid

The circles in the figure represent particles and their regular arrangement shows the crystalline structure.

Amorphous solid

Unlike crystalline solids, amorphous solids do not have long-range order. Their particles are not arranged in regular patterns. Instead, they are arranged randomly, which is why they have no obvious shape. Examples include glass and plastic.

Chemical bonding in solids

The properties of solids are determined mainly by the type of chemical bonds that hold the particles together.

  • Ionic solids: These are formed by ions held together by ionic bonds. Examples include sodium chloride (NaCl) and magnesium oxide (MgO).
  • Covalent network solids: The atoms in these solids are linked by a network of covalent bonds. Examples include diamond and quartz.
  • Metallic solids: consist of metal cations surrounded by a "sea" of delocalized electrons. This structure explains the properties such as conductivity and malleability found in metals such as copper and aluminum.
  • Molecular solids: held together by intermolecular forces such as London dispersion, dipole-dipole interactions, or hydrogen bonding. Examples include ice (H2O) and solid carbon dioxide (CO2).

Examples of solids in daily life

Solids play an important role in our daily lives. Here are some examples of how we encounter solids in our daily lives:

  • Furniture like tables and chairs in our homes are solid objects.
  • The screen you are using to read this text is made of solids.
  • In addition, solid substances such as minerals are important in the formation of rocks.
  • Food items such as bread and butter are also examples of solids.

The role of solids in nature

Solids are important in nature, forming the physical structure of the Earth and things inside it. The Earth's crust is composed primarily of solid rocks and minerals. These solids form mountains, valleys, and various landforms. In addition, living organisms, including plants and animals, depend on solid structures for support and protection.

Physical changes in solids

Solids can also undergo physical changes without changing their chemical composition. Here are some examples:

  • Melting: When a solid is heated, it can change into a liquid. This change occurs when the particles in the solid gain enough energy to be released from their fixed positions. A common example is ice melting into water.
  • Sublimation: Some solid substances can change directly into gases without first going into the liquid state. A classic example of this phenomenon is dry ice (CO2) which sublimes directly from the solid state to the gaseous state.

Importance of solids in technology

Solids play an important role in technology and industry. For example:

  • Semiconductors: Solid materials such as silicon are used in electronic devices because of their semiconductor properties.
  • Construction materials: Solid materials such as steel and concrete are essential in building infrastructure.
  • Metallurgy: The study and manipulation of metals is important in industries such as automotive and aerospace.

Conclusion

Understanding the solid state is fundamental to the study of matter and chemistry. The properties of solids, from their hardness to their incompressibility, arise from the way their atoms are structured and bonded. Whether in nature, technology or our everyday lives, solids are indispensable, highlighting the importance of chemistry and the study of the different states of matter.


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Solid state

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