Unit 3 General Chemistry (Chem 1102).pptx

chemistry chapter 3 for freshman in kotebe university of education

1. General Chemistry ( Chem 1102 ) Chapter 3 Matter and Change

2. Matter Definition of Matter Matter refers to anything that occupies space and has mass. It is the physical substance that makes up the universe and all the objects within it. Matter can exist in various forms, including solid, liquid, gas, or plasma, and it is composed of tiny particles called atoms.

3. Atoms are the building blocks of matter and consist of a nucleus, which contains positively charged protons and neutral neutrons, as well as negatively charged electrons that orbit the nucleus. The specific arrangement and combination of atoms determine the properties and characteristics of different types of matter.

4. Energy Energy is a fundamental concept in physics that refers to the ability of a system to do work or cause a change. It is a scalar quantity, meaning it has magnitude but no direction. Energy exists in various forms and can be transformed from one form to another.

5. The relationship between energy and matter: The relationship between matter and energy can e described by the famous equation proposed by Albert Einstein, known as the mass-energy equivalence principle or simply E=mc². This equation states that energy (E) is equal to the mass (m) of an object multiplied by the square of the speed of light (c) in a vacuum. In other words, mass and energy are interchangeable and can be converted into each other.

6. Properties of matter Properties of substances refer to the characteristics or attributes that can be used to describe and identify them. These properties can be classified into two main categories: Physical properties and Chemical properties.

7. Physical properties Physical properties are those that can be observed or measured without changing the chemical composition of the substance.

8. Examples of physical properties include: Density: The mass of a substance per unit volume. Melting point: The temperature at which a substance changes from a solid to a liquid state. Boiling point: The temperature at which a substance changes from a liquid to a gaseous state. Color: The visual appearance of a substance. Odor: The characteristic smell of a substance. Solubility: The ability of a substance to dissolve in a particular solvent. Conductivity: The ability of a substance to conduct heat or electricity. Hardness: The resistance of a substance to being scratched or dented.

9. Intensive and Extensive properties of matter: Intensive and extensive properties are classifications used to characterize and describe different types of properties of matter. Intensive Properties: Intensive properties are independent of the amount or size of the sample being observed. These properties describe the inherent characteristics of a substance, regardless of the quantity of the substance present.

10. Examples of intensive properties include: Temperature: The measure of the average kinetic energy of particles in a substance. Density: The mass per unit volume of a substance. Color: The visual appearance of a substance. Melting point: The temperature at which a substance changes from a solid to a liquid state. Boiling point: The temperature at which a substance changes from a liquid to a gaseous state. Refractive index: The extent to which light is bent when passing through a substance. Specific heat capacity: The amount of heat energy required to raise the temperature of a substance by a certain amount.

11. Examples of extensive properties include: Mass: The amount of matter in a substance. Volume: The amount of space occupied by a substance. Total energy: The sum of all forms of energy (kinetic, potential, etc.) possessed by a substance. Total charge: The net electric charge of a substance. Total heat capacity: The total amount of heat energy required to raise the temperature of a substance by a certain amount. Extensive Properties: Extensive properties depend on the amount or size of the sample being observed. These properties change as the quantity of the substance changes.

12. Chemical Properties Chemical properties describe how a substance interacts or reacts with other substances, leading to changes in its chemical composition.

13. Examples of chemical properties include: Reactivity: The ability of a substance to undergo chemical reactions with other substances. Flammability: The tendency of a substance to burn or ignite in the presence of a flame. Oxidation: The ability of a substance to react with oxygen, often resulting in the formation of oxides. pH: The measure of acidity or alkalinity of a substance. Stability: The tendency of a substance to remain unchanged or undergo decomposition over time. Toxicity: The degree to which a substance can cause harm or toxicity to living organisms .

14. States of matter Matter is classified into different types based on its composition and properties. The three main states of matter are: Solid, Liquid an Gas. Solid: In this state, matter has a definite shape and volume. The particles in a solid are tightly packed together and vibrate in fixed positions.

15. Liquid: Liquids have a definite volume but take the shape of their container. The particles in a liquid are close together but have more freedom to move and flow past one another.

16. Gas: Gases have neither a definite shape nor a definite volume. The particles in a gas are widely spaced and move freely, colliding with each other and the walls of the container.

17. There is also a fourth state of matter called plasma, which is a highly ionized gas consisting of charged particles. Plasma is commonly found in stars and other high-energy environments.

18. Changes in matter and energy Changes in matter and energy refer to the transformations and interactions that occur within physical systems. Matter can undergo various changes, such as physical changes and chemical changes, while energy can be transferred or transformed from one form to another.

19. Physical Changes: Physical changes involve alterations in the physical state or properties of matter without changing its chemical composition. Examples of physical changes include: changes in state (e.g., melting, freezing, vaporization, condensation), changes in shape or size (e.g., cutting, grinding, crushing), and changes in physical properties (e.g., changes in color, density, solubility) that do not result in the formation of new substances. Physical changes are usually reversible, meaning the original substance can be recovered. Changes in Matter:

20. Chemical Changes: Chemical changes, also known as chemical reactions, involve the transformation of one or more substances into new substances with different chemical compositions. Chemical changes typically involve the breaking and forming of chemical bonds. Examples of chemical changes include: combustion, oxidation, decomposition, and various types of reactions, such as acid-base reactions and precipitation reactions. Chemical changes are usually accompanied by the release or absorption of energy.

21. Changes in Energy: Energy can undergo various changes, including transfer and transformation. Energy transfer refers to the movement of energy from one object or system to another without any change in its form or type. Energy transformation involves the conversion of energy from one form to another. Forms of energy include kinetic energy (energy of motion), potential energy (energy stored due to position or condition), thermal energy (heat energy), electromagnetic energy (energy carried by electromagnetic waves), chemical energy (energy stored in chemical bonds), and many others.

22. Energy can be transferred and transformed through various processes, such as mechanical work, heat transfer, electromagnetic radiation, and chemical reactions. The law of conservation of energy states that energy cannot be created or destroyed; it can only be transferred or transformed from one form to another.

23. Classification of matter based on composition: Based on its composition matter can classified in to elements, compounds, and mixtures. Have a Constant composition. Have no a constant composition

24. Elements: Elements are pure substances that cannot be chemically broken down into simpler substances. Each element is made up of atoms with the same atomic number. Examples of elements include: Hydrogen (H), Oxygen (O), Carbon (C), and Gold (Au). Elements are listed on the periodic table, which arranges them based on their atomic number.

25. Compounds: Compounds are substances composed of two or more different elements chemically combined in fixed ratios. Compounds have properties distinct from those of their constituent elements. Examples of compounds include: Water (H 2 O), Carbon dioxide (CO 2 ), and Sodium chloride (NaCl).

26. Mixtures: Mixtures are combinations of two or more substances that are physically intermingled but not chemically bonded. The components of mixtures can be separated by physical means, such as filtration, distillation, or evaporation. Mixtures can be further classified into two types: Homogeneous mixtures (solutions): Uniformly mixed throughout, with no visible boundaries between the components. Examples include saltwater and air. Heterogeneous mixtures: Not uniformly mixed , with distinct visible boundaries between the components. Examples include salad dressing and granite.

27. Techniques of separation of components of mixtures Techniques of separation are used to isolate and purify the components of mixtures by taking advantage of their different physical properties. Filtration: Filtration is a method used to separate solid particles from a liquid or gas by passing the mixture through a porous material called a filter. The filter allows the liquid or gas to pass through while retaining the solid particles. Filtration is commonly used to separate suspended solids from liquids or to remove solid impurities from a gas stream.

28. Decantation:(kerera) Decantation is a process of separating a mixture of solid particles and a liquid by carefully pouring off the liquid, leaving the solid particles behind. It is typically used when the solid particles settle at the bottom of the container due to their higher density or gravity. Decantation is often used for separating a mixture of solids and liquids that do not form a homogeneous mixture.

29. Evaporation: Evaporation is a technique used to separate a soluble solid from a liquid by heating the mixture, causing the liquid to vaporize and leaving behind the solid. The liquid is heated until it reaches its boiling point, and the vapor is collected or allowed to escape, leaving the solid residue. Evaporation is commonly employed to obtain salts from their solutions or to separate volatile components from non-volatile substances .

30. Distillation: Distillation is a process that utilizes differences in boiling points to separate a mixture of liquids or a liquid from a solution. The mixture is heated, and the component with the lower boiling point vaporizes first. The vapor is then collected and condensed back into a liquid. Distillation is often used to obtain pure water from a saline solution or to separate different components of a mixture with different boiling points, such as ethanol from a fermented mixture.

31. Crystallization: Crystallization is a technique used to separate a dissolved solid from a liquid by cooling the mixture, allowing the solid to form crystals and separate from the liquid. By controlling the cooling rate and conditions, desired crystals can be obtained. Crystallization is commonly used to purify substances and obtain highly pure solid compounds.