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


Matter is everything that has mass and occupies space. Everything around us is made of matter, whether it's the air we breathe or the food we eat. One of the most important concepts in understanding matter is its states. Matter can exist in many different forms, commonly called states. The three most familiar states of matter are solid, liquid, and gas. There are also other states of matter, such as plasma and Bose-Einstein condensates, but in this lesson, we'll focus on solids, liquids, and gases, since these are the states we encounter most often in everyday life.

Solids

Solids are one of the most easily recognizable states of matter. They have a definite shape and volume. This means that a solid object, such as a rock or a pencil, maintains its shape no matter what container it is in. This is because the particles in a solid are packed tightly together, usually in a pattern. The particles do not move freely, but rather vibrate in place. This fixed position of the particles contributes to the stiffness of solids.

To understand solids better, imagine a box tightly packed with marbles. The marbles cannot move around freely because there is no space. This is similar to particles in solids.


// Solid particles arranged tightly
OOO
OOO
OOO

Solids can be classified into two types: crystalline solids and amorphous solids. Crystalline solids have well-organized structures and include materials such as salt and diamond. Amorphous solids such as glass and plastic have no specific arrangement and their particles are not even organized.

Liquids

Liquids are a state of matter that has a definite volume but no definite shape. This means that they take the shape of the container they are in. Unlike solids, the particles in liquids are not so tightly packed, so they can move by sliding past each other. This motion gives liquids the ability to flow.

A useful analogy for understanding fluids is a bowl of jellybeans. Even when the jellybeans are packed together, you can still move them around within the bowl. The same principle applies to fluid particles.


// Liquid particles with a bit more space to move
OOOO
OOOOOOO

Gases

Gases are an interesting state of matter because they have no definite shape or volume. Gases expand to fill the shape and volume of their container. This happens because gas particles are much farther apart than solids and liquids. The particles move freely and quickly, which is why gases can expand quickly until they fill a space evenly.

Imagine a jar filled with ping-pong balls. If you shake the jar, the balls will randomly fill the entire space. This shows how gas particles behave.


// Gas particles, widely spaced and free to move
OOOOOO

Changing states

Matter can change from one state to another when physical conditions such as temperature or pressure change. These changes are called phase changes. Some common phase changes are as follows:

  • Melting: When a solid changes into a liquid. For example, when ice melts to become water.
  • Freezing: When a liquid turns into a solid. For example, when water freezes into ice.
  • Evaporation: When a liquid changes into a gas, such as water boiling and turning into steam.
  • Condensation: When a gas changes into a liquid, such as when steam cools and turns back into water.

Temperature and pressure play an important role in these changes:

  • An increase in temperature usually provides energy for particles to move more and to change into a less ordered state (e.g., from a solid to a liquid).
  • Lowering the temperature generally dissipates energy, causing the particles to slow down and become more ordered (for example, from a gas to a liquid).

Examples from daily life

States of matter and the changes between them can be seen in many everyday activities and objects. Here are some examples:

  • Solids: Ice cubes in drinks, furniture, and many food items such as chocolate.
  • Liquid: Water is most commonly referred to as a liquid, but beverages such as milk and juice are also examples.
  • Gas: The air we breathe is a mixture of gases, including oxygen and nitrogen. Balloons filled with helium gas float because helium is lighter than air.

Conclusion

Understanding the states of matter is fundamental to the study of chemistry and physics. Transitions between solids, liquids, and gases involve changes in energy and provide insight into the nature of matter around us. From the relatively stable structures of solids to the freedom of gases, each state exhibits its own unique properties and behaviors, and these form the basis of most physical interactions and phenomena in the world.


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States of matter

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