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 ↓


Fluid state


In our daily lives, we see matter in three primary states: solid, liquid, and gas. Each of these states has unique characteristics that distinguish one from the other. In this comprehensive guide, we will explore the liquid state, a fascinating phase of matter found in abundance all around us.

What is fluid?

Liquid is one of the states of matter that has a definite volume but no definite shape. This means that the liquid takes the shape of the container it is in but its volume remains the same. Common examples of liquids include water, milk, and oil.

Text examples of liquids:

  • Water: Found in oceans, rivers and rain.
  • Milk: A daily use item in many households.
  • Oil: Used in cooking and industry.

Properties of liquids

Let's take a deeper look at the distinctive features of liquids:

1. Fixed quantity

Liquids have a fixed volume. No matter where you pour the liquid or how much you pour, the volume will remain the same. For example, if you pour 500 milliliters of water into different shaped vessels, it will always measure 500 milliliters.

2. Indefinite shape

Unlike solids, liquids have no fixed shape. Instead, they flow and mold to the shape of their container. Pour water from a bottle into a glass, and you'll see it take the shape of the glass.

3. Liquidity

Liquids can flow. This property is known as fluidity. Because of this, they can easily move from one container to another. Fluidity is what allows water to flow out of a tap or river and continue on its way.

4. Surface tension

Liquids have a unique property called surface tension. It is the tendency of liquid surfaces to shrink to a minimum surface area. This is why small insects can walk on water and raindrops form round beads on surfaces.

5. Stickiness

Viscosity is a measure of a fluid's resistance to flow. Thick fluids, such as honey, have high viscosity, while thin fluids, such as water, have low viscosity. Viscosity affects how fast or slow a fluid flows.

Molecular structure of liquids

The molecules in liquids are more tightly packed than those in gases, but do not have a rigid structure like solids. Intermolecular forces in liquids are strong enough to keep the molecules close together, yet weak enough to allow them to move freely around each other.

Intermolecular forces

These are the forces that hold molecules together. They play a key role in determining the boiling and melting points of liquids. For example, water has strong hydrogen bonds, which account for its relatively high boiling point compared to other liquids.

H2O (solid) ⟶ H2O (liquid) ⟶ H2O (gas)

How does a liquid change its state

Liquids can change their state through various processes such as freezing, boiling, evaporation, and condensation:

1. Cold

Ice freezes when a liquid turns into a solid. For example, water turns into ice when the temperature drops below 0°C (32°F).

2. Boiling

Boiling occurs when a liquid turns into a gas at a certain temperature, called the boiling point. For water, this occurs at 100°C (212°F) at sea level.

3. Evaporation

Evaporation is a slow process in which a liquid turns into a gas at a temperature below its boiling point. This is how puddles of water dry up on a sunny day.

4. Condensation

Condensation is the process by which a gas turns into a liquid. This happens with water vapor present in the air that forms dew on cold surfaces at night.

Real-life applications of fluids

Fluids play an important role in many everyday applications:

In transport

Fluids such as gasoline and diesel are essential for vehicles to run. Brake fluid and engine oil are also essential for machines to function properly.

In household activities

Liquids such as water and cleaning agents are used daily for cooking, cleaning and bathing. Various liquid soaps and detergents help maintain hygiene.

In food and beverage

Many beverages are liquids, such as juices, tea, and coffee. The preparation of many foods also involves the use of liquids, such as water, oil, and broth.

Conclusion

Understanding the liquid state of matter provides insight into a fundamental aspect of our world and its practical applications in everyday life. Liquids bridge the gap between the rigidity of solids and the extensibility of gases, creating a unique balance that supports life and influences countless processes.


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Fluid state

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