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 → Elements, Compounds, and Mixtures ↓


Types of mixtures


A mixture is a combination of two or more substances where each substance retains its chemical identity. In chemistry, it is important to understand mixtures and their types as they help us understand the fundamental concepts of matter. Every substance we encounter in our daily life is either a pure substance (elements and compounds) or a mixture.

Elements and compounds

Before delving deeper into mixtures, let's briefly explain what elements and compounds are:

  • Elements: Elements are pure substances that contain only one type of atom. They are the simplest form of matter and cannot be broken down into simpler substances by chemical means. For example, gold (Au), oxygen (O 2), and hydrogen (H 2) are elements.
  • Compounds: Compounds are substances that are formed when two or more elements are chemically joined together. Their proportions are fixed, and the chemical identities of the elements change when they form compounds. For example, water (H 2 O) is a compound made of hydrogen and oxygen.

Mixture

A mixture is a physical combination of two or more substances, where each substance retains its individual properties. Unlike compounds, the substances in a mixture are not chemically linked and can be separated by physical methods. Mixtures are classified into two main types: homogeneous mixtures and heterogeneous mixtures.

Homogeneous mixture

Homogeneous mixtures are mixtures that have a uniform composition. They appear as a single substance, even though they contain multiple substances. The substances within a homogeneous mixture are so thoroughly mixed that you cannot see the separate parts. These mixtures are also called solutions.

Example:

  • Sugar water: When sugar is dissolved in water, it becomes a solution. Every flavor of sugar water will be the same, reflecting its uniform composition.
  • Air: Air is a homogeneous mixture of gases. It mainly consists of nitrogen, oxygen, carbon dioxide and other minor gases.
  • Alloys: Alloys such as bronze (an alloy of copper and tin) and steel (an alloy of iron and carbon) are examples of homogeneous metal mixtures.
Note: In solutions, the substance present in the greatest quantity is called the solvent, and the substances that are dissolved in the solvent are known as solutes.

Visual representation of homogeneous mixture:

Water (solvent)sugar (solute)Sugar Water as a Solution

Heterogeneous mixtures

Heterogeneous mixtures are mixtures that do not have a uniform composition. The different components can be easily seen and separated through physical means. They often consist of two or more phases or layers.

Example:

  • Salad: Salad is a mixture of various vegetables such as lettuce, tomatoes and cucumbers. You can see and choose each ingredient.
  • Sand and iron filings: When sand is mixed with iron filings, the mixture is heterogeneous, as sand and iron filings can be seen separately.
  • Oil and water: When oil is mixed with water, two distinct layers are formed, showing the characteristics of a heterogeneous mixture.

Visual representation of heterogeneous mixtures:

Characteristics of the mixture

Mixtures display a set of characteristics that help distinguish them from pure substances:

  • The components of a mixture retain their original properties. For example, the sour taste of lemon juice is retained even when mixed with water.
  • The components of a mixture may be separated by physical methods such as filtration, evaporation, or sieving.
  • Mixtures do not have any fixed composition. For example, in making a fruit salad, any proportion of fruits can be used.
  • Energy is neither released nor absorbed to form a mixture, while compounds are formed in chemical reactions.

Separating components of a mixture

The components of a mixture can be separated using various physical methods. Here are some common techniques:

  • Filtration: Used to separate insoluble solids from a liquid. For example, sand can be separated from a mixture of sand and water by filtration.
  • Evaporation: allows the solute to separate from the solvent by heating the solution until the solvent evaporates, leaving the solute behind, such as obtaining salt from salt water.
  • Distillation: This involves heating a liquid to form a vapor and then cooling the vapor to form a liquid, used to separate mixtures based on differences in boiling points, such as purifying water from a salt solution.
  • Magnetic separation: This involves using magnets to separate magnetic substances from non-magnetic substances, such as separating iron filings from sand.
  • Chromatography: Used to separate the colors in a dye, showing the different components based on their different absorption rates.

Real-life mixing examples

Mixtures abound in everyday life. Here are some real examples:

  • Milk: Milk is a colloidal heterogeneous mixture containing water, fat, proteins and lactose.
  • Blood: Blood is a complex mixture of cells, plasma, and various dissolved solutes.
  • Seawater: A homogeneous mixture of various salts dissolved in water.
  • Cement: A mixture of gypsum, concrete, sand, and water, often used in construction.

Conclusion

Mixtures play an important role in both nature and human industry. The study of mixtures, their characteristics, types and separation techniques is fundamental to understanding chemistry and the complex nature of the substances around us. Exploring mixtures helps us understand the variety of materials we use everyday, from the simple task of making tea to complex processes in chemical plants.


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Types of mixtures

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