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


In the world around us, most of the matter we see, touch, and use every day can be divided into three main categories: elements, compounds, and mixtures. Understanding these categories and how they differ helps us understand the structure and properties of the things that make up our universe. Let's look at each of these categories in detail.

Elements

Elements are pure substances that contain only one type of atom. They are the building blocks of all matter and cannot be broken down into simpler substances by chemical means. Each element has its own unique properties and is represented by a chemical symbol, such as H for hydrogen, O for oxygen, and Fe for iron.

Visual example of an element

Imagine a container filled with oxygen gas. All the particles inside are atoms of oxygen.

Hey Hey Hey

Elements can exist in different forms, such as solid, liquid, or gas, depending on the temperature and pressure conditions. For example, at room temperature, mercury is a liquid, while most metals are solids.

Compounds

Compounds are substances that are formed when two or more elements are chemically joined together. Their properties are different from the individual elements they are made of. For example, water is a compound made of hydrogen and oxygen, and it behaves very differently from these two gases.

The chemical formula of a compound shows which elements it contains and how many atoms of each element are present. For example, the chemical formula for water is H2O, which means that each molecule has 2 hydrogen atoms and 1 oxygen atom.

Visual example of compound

Consider a water molecule, which has two hydrogen atoms bonded to one oxygen atom.

Hey H H

Compounds can be broken down into simpler substances by chemical means, such as heating or applying an electric current. A well-known example of this is the splitting of water into hydrogen and oxygen gases through a process called electrolysis.

Mixture

Mixtures are substances made up of two or more substances, which can be elements or compounds, that are physically combined. Unlike compounds, the components of a mixture retain their own properties and can be separated by physical means.

Mixtures can be homogeneous or heterogeneous. Homogeneous mixtures have a uniform composition, such as salt water. Heterogeneous mixtures have distinct, visible parts, such as a salad.

Visual example of mixing

Think of a mixture of salt and sand. The two can be seen as separate.

S sodium chloride S sodium chloride

Some common methods of separating mixtures include filtration (separating solids from liquids), distillation (separating substances based on boiling point) and magnetism (separating magnetic substances).

Classification of everyday substances

Understanding what elements, compounds, and mixtures are helps us better understand the materials around us. Let's classify some common substances:

  • Gold (Au): An element. It is a pure metal found in its natural state.
  • Table salt (NaCl): A compound. It is made up of the elements sodium and chlorine.
  • Air: A mixture. It contains various gases such as nitrogen, oxygen, and carbon dioxide.
  • Carbon dioxide (CO2): A compound. It is made up of carbon and oxygen.
  • Milk: A mixture. It contains water, fat, protein and sugar.

By recognizing these categories, we can understand the diversity of chemical structures in substances and their interactions in daily life.

The importance of understanding elements, compounds, and mixtures

Scientists and researchers use their understanding of elements, compounds, and mixtures to create new materials and solve problems. For example, knowing the properties of different elements helps create stronger alloys and investigate chemical reactions.

In industries, it is important to separate mixtures to obtain pure substances. The pharmaceutical industry often uses knowledge of compound chemistry to create and test new medicines.

Summary

Elements, compounds, and mixtures are fundamental concepts in chemistry that explain how different substances are composed and classified. Elements are pure substances containing only one type of atom. Compounds are made up of elements that are chemically bonded, and mixtures contain two or more substances that are physically combined.

Learning about them gives us a better understanding of the physical world and how it can be used for various purposes. This knowledge is important in fields ranging from environmental science to engineering and medicine.


Grade 7 → 3


U
username
0%
completed in Grade 7

← Prev (2.7)
Diffusion and its importance
Next (3.1) →
Definition of the element

Comments 



Elements, Compounds, and Mixtures

https://www.chemistryelite.com/g7/3?ceal=en