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 → Water and its importance ↓


Importance of water for life


Water is a colorless, tasteless and odorless liquid that is vital to all forms of life on Earth. It covers about 71% of the Earth's surface and is a major component of living cells. In this topic, we will explore why water is so important for the existence and nourishment of life.

Chemical nature of water

Water is a chemical compound with the formula H2O. This means that each molecule of water is made up of two hydrogen atoms bonded to one oxygen atom. Water's unique properties arise from its molecular structure. Below is an illustration of a water molecule:

    Hey
   ,
  HH

The oxygen atom is more electronegative than the hydrogen atoms, which means it pulls electrons more strongly. This gives the oxygen a slightly negative charge and the hydrogen atom a slightly positive charge, making water a polar molecule.

Properties of water

Water has several unique properties that make it indispensable for life:

Cohesion and surface tension

Adhesion refers to the attraction between molecules of the same substance. Since water molecules are polar, they stick to one another. This results in surface tension, which allows small insects to walk on water without sinking.

Imagine a drop of water placed on a leaf forms a pearl-like shape due to surface tension. Without this surface tension, the water would spread out, and life as we know it could not exist.

Adhesion

Adhesion is another important property of water. It is the attraction between water molecules and other types of molecules. It explains why water can rise up thin tubes against gravity, a phenomenon known as capillary action.

Plants use capillary action to transport water from their roots to their leaves, which is necessary for photosynthesis and nutrient delivery.

High specific heat capacity

The specific heat capacity of water is the amount of heat needed to raise the temperature of 1 gram of water by 1 degree Celsius. Water has a very high specific heat capacity, which means it can absorb a lot of heat without seeing a significant increase in temperature.

Absorbed heat

This property helps regulate the Earth's climate and enables organisms to maintain a stable internal temperature despite external temperature changes.

Universal solvent

The polarity of water makes it an excellent solvent. It can dissolve a wide variety of substances, which is why it is often called the "universal solvent." When salt (NaCl) dissolves in water, the Na+ and Cl- ions interact with the water molecules and diffuse out:

    NaCl (s) ⟶ Na+ (aq) + Cl- (aq)

This property is important for biochemical reactions, as it helps transport nutrients, minerals and gases through our bodies.

The role of water in biological processes

Water is central to many biological processes:

Photosynthesis

Photosynthesis is the process by which green plants, algae, and some bacteria synthesize food using sunlight. This process requires water, carbon dioxide, and sunlight. The chemical equation is:

    6CO2 + 6H2O + light energy ⟶ C6H12O6 + 6O2

Water acts as an electron donor in this process. This reaction releases oxygen, which is essential for life on Earth.

Cellular respiration

Cellular respiration is the process by which cells convert nutrients into energy. Water is a product of cellular respiration and is essential in energy production:

    C6H12O6 + 6O2 ⟶ 6CO2 + 6H2O + ATP (Energy)

Water produced in cellular respiration is important for maintaining cellular homeostasis and for the transport of nutrients.

Temperature

Water's high specific heat capacity helps organisms regulate temperature. For example, through sweating, humans can expel excess body heat because water absorbs and carries away a large amount of heat when it evaporates from the skin's surface.

Imagine a hot day when your body sweats to expel excess heat, preventing the body from overheating.

Water in the human body

The human body consists of about 60% water. Water is an important component of our bodily fluids and serves many functions:

Transportation

Water is the main component of blood. It transports oxygen, nutrients, and waste products to and from cells. Without enough water, these vital processes will come to a standstill.

Lubrication

Water provides lubrication to joints and is the main component of saliva and mucus. These fluids ensure smooth movement and digestion.

Hydration and metabolism

Water is important for proper hydration, which is vital for metabolism and overall health. It aids in the digestion, absorption, and excretion processes within the body.

Importance of water conservation

Although water is abundant on Earth, only a small portion of it is usable fresh water. It is essential to preserve this precious resource to ensure its availability for future generations. Simple habits like fixing leaks, using water-saving devices, and being mindful of consumption can go a long way.

In conclusion, water is the basis for life on Earth. Its unique properties and roles in biological processes make it indispensable for the survival of living organisms and the health of ecosystems. Understanding the importance of water in life helps us appreciate and preserve this precious resource.


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