CHM 101 — General Chemistry I: Lecture Note

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LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Course code: CHM 101 Course Title: General Chemistry I Course Unit: 2 Units Series 1: Foundations of Atoms, Molecules, and Chemical Reactions Part 1 Atoms and Molecules: The Building Blocks of Matter • Definition and concept of atoms • Molecules and compounds • Elements and symbols Part 2 Chemical Reactions and Equations • Nature of chemical reactions • Types of chemical reactions (combination, decomposition, displacement, exchange) • Writing and balancing chemical equations Part 3 Stoichiometry and Quantitative Relationships • The mole concept • Mass, volume, and particle relationships in reactions • Applications of stoichiometry in problem solving Part 4 Introduction to Redox Reactions • Oxidation and reduction definitions • Identifying oxidising and reducing agents • Balancing simple redox equations Introduction Chemistry begins with the smallest units of matter that make up everything around us. From the air we breathe to the food we eat, all substances are composed of atoms and molecules that interact through chemical reactions. Understanding these fundamental concepts provides the foundation upon which the rest of chemistry is built. This Series will therefore introduce you to the essential principles that explain how matter is structured and how it changes, preparing you for deeper exploration in subsequent Series.

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS The aim of this Series is to equip you with the knowledge and skills needed to define atoms and molecules, describe their interactions, and apply the principles of chemical equations and stoichiometry to real problems. By the end of this Series, you will be able to explain the basic building blocks of matter and demonstrate how chemical reactions are represented and analysed. We shall commence this Series by examining atoms and molecules as the basic building blocks of matter. Next, we will move on to chemical reactions and equations, where you will learn how to classify, write, and balance them. Following that, we will explore stoichiometry and quantitative relationships, focusing on the mole concept and its applications in problem solving. Finally, we will wrap up by introducing redox reactions, where you will identify oxidation and reduction processes and practise balancing simple redox equations. Series Learning Outcomes Upon completing this Series, you should be able to: • SLO 1.1 define atoms and molecules as the fundamental building blocks of matter, • SLO 1.2 explain the distinction between elements, compounds, and their symbolic representations, • SLO 1.3 describe the nature and types of chemical reactions, • SLO 1.4 demonstrate how to write and balance chemical equations accurately, • SLO 1.5 apply the mole concept to calculate mass, volume, and particle relationships in chemical reactions, • SLO 1.6 analyse stoichiometric problems to determine quantitative relationships in reactions, and • SLO 1.7 identify oxidation and reduction processes and balance simple redox equations. 1.1 Atoms and Molecules: The Building Blocks of Matter 1.1.1 Definition and concept of atoms An atom is the smallest unit of an element that retains the chemical properties of that element. It consists of a nucleus, which contains positively charged protons and neutral neutrons, surrounded by negatively charged electrons that occupy specific energy levels. Atoms are the fundamental units of matter and combine in various ways to form molecules and compounds. Atoms are incredibly small, yet they form the basis of all substances. For example, the water you drink is made up of atoms of hydrogen and oxygen bonded together. Fill in the blank: The smallest unit of an element that retains its chemical properties is called an ______.

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS 1.1.2 Molecules and compounds A molecule is a group of two or more atoms held together by chemical bonds. Molecules may consist of atoms of the same element, such as oxygen gas (O₂), or atoms of different elements, such as water (H₂O). A compound is a substance formed when atoms of different elements combine in fixed proportions. Compounds have properties distinct from the individual elements that make them up. For instance, sodium is a reactive metal and chlorine is a poisonous gas, yet together they form sodium chloride (NaCl), which is common table salt. Fill in the blank: A substance formed when atoms of different elements combine in fixed proportions is called a ______. 1.1.3 Elements and symbols An element is a pure substance made up of only one type of atom. Each element is represented by a unique chemical symbol, usually derived from its English or Latin name. For example, hydrogen is represented by H, oxygen by O, and sodium by Na (from the Latin word natrium). The periodic table provides a systematic arrangement of all known elements, each with its symbol, atomic number, and other properties. Learning these symbols is essential for writing chemical equations and understanding chemical reactions. Fill in the blank: The chemical symbol for sodium is derived from its Latin name, ______. Element Symbol Hydrogen H Carbon C Nitrogen N Oxygen O Sodium Na Magnesium Mg Aluminium Al Silicon Si Phosphorus P Sulfur S Chlorine Cl Potassium K Calcium Ca Iron Fe Copper Cu Zinc Zn Silver Ag Gold Au Mercury Hg Lead Pb

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS Table 1.1: Selected elements and their symbols Pilot questions 1.1 1. Which subatomic particles are found in the nucleus of an atom? 2. What is the smallest unit of matter that retains the properties of an element? 3. Give one example of a molecule made up of atoms of the same element. 4. What is the difference between a molecule and a compound? 5. Write the chemical symbol for chlorine. 1.2 Chemical Reactions and Equations 1.2.1 Nature of chemical reactions A chemical reaction is a process in which one or more substances, called reactants, are transformed into new substances, called products. During a chemical reaction, bonds between atoms are broken and new bonds are formed, resulting in changes in composition and properties. For example, when hydrogen reacts with oxygen, water is formed. Chemical reactions are central to chemistry because they explain how substances interact and change. They can involve energy changes, such as the release of heat in combustion or the absorption of energy in photosynthesis. Fill in the blank: Substances that undergo change in a chemical reaction are called ______. 1.2.2 Types of chemical reactions Chemical reactions can be classified into several types: • Combination reaction: Two or more substances combine to form a single product. Example: 2H₂ + O₂ → 2H₂O. • Decomposition reaction: A single compound breaks down into two or more simpler substances. Example: 2HgO → 2Hg + O₂. • Displacement reaction: One element replaces another in a compound. Example: Zn + CuSO₄ → ZnSO₄ + Cu. • Exchange (double displacement) reaction: Two compounds exchange ions to form new compounds. Example: NaCl + AgNO₃ → NaNO₃ + AgCl. Fill in the blank: A reaction in which a single compound breaks down into simpler substances is called a ______ reaction. [Insert box placeholder here] Caption: Box 1.1: Summary of types of chemical reactions

LA-NET | ONLINE LEARNING VIDEO PLATFORM FOR POST-SECONDARY & HIGHER INSTITUTION STUDENTS • Box listing combination, decomposition, displacement, and exchange reactions with examples • Suggested AI prompt: “Create a summary box listing four types of chemical reactions with examples.” • Search string: “OER summary types of chemical reactions examples” 1.2.3 Writing and balancing chemical equations A chemical equation is a symbolic representation of a chemical reaction, showing the reactants, products, and their relative amounts. Balancing chemical equations ensures that the law of conservation of mass is obeyed, meaning the number of atoms of each element is the same on both sides of the equation. To balance an equation, coefficients are placed before chemical formulas to adjust the number of atoms. For example, the combustion of methane is written as: CH₄ + 2O₂ → CO₂ + 2H₂O. Balancing equations requires practice and careful attention to detail. Always begin with the most complex molecule and adjust coefficients systematically. Fill in the blank: The principle that requires the number of atoms of each element to be equal on both sides of a chemical equation is called the law of ______. Pilot questions 1.2 1. What is the difference between reactants and products in a chemical reaction? 2. Write one example of a combination reaction. 3. Which type of reaction involves the exchange of ions between two compounds? 4. Why must chemical equations be balanced? 5. Balance the equation: H₂ + O₂ → H₂O. 1.3 Stoichiometry and Quantitative Relationships 1.3.1 The mole concept The mole is a fundamental unit in chemistry used to measure the amount of substance. One mole contains 6.022×1023particles, which may be atoms, molecules, or ions. This number is known as Avogadro’s constant. The mole allows chemists to relate the microscopic world of atoms and molecules to measurable quantities in the laboratory. For example, one mole of water

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