General Chemistry: Matter and Its Properties

Introduction to General Chemistry

• Definition of General Chemistry: A branch of science that focuses on the composition, structure, properties, and changes of matter.
• Key Topics in General Chemistry:
  • Matter and Its Properties: Covers the states of matter and both physical and chemical properties.
  • Atoms and Elements: Includes the structure of the atom, the periodic table, and isotopes.
  • Chemical Bonding: Examination of ionic and covalent bonds and various molecular shapes.
  • Chemical Reactions: Different types of reactions and the methods for balancing chemical equations.
  • Stoichiometry: Focuses on the mole concept and calculations involving chemical reactions.
  • States of Matter: Study of solids, liquids, gases, and the specific gas laws.
  • Solutions and Mixtures: Analysis of concentration levels, solubility, and different types of mixtures.
  • Acids and Bases: Concepts of pH, neutralization processes, and chemical indicators.
  • Thermochemistry: The study of heat exchange and energy during chemical reactions.
  • Basic Nuclear Chemistry: Involves radioactivity and nuclear reactions (dependent on specific curriculum requirements).

Lesson 1: Matter and Its Properties

• Most Essential Learning Competency (MELC): Use properties of matter to identify substances and separate them.
• Curriculum Code: $STEM\_GC11MPla-b-5$
• Conceptual Examples (Morphin Time):
  • Melting of Ice: Observing changes in state and physical characteristics.
  • Burning of Wood: Observing changes in chemical composition and identity.
• Definition of Properties: These refer to the distinguishing characteristics used to identify a specific material.

Classification of Properties of Matter

Properties are grouped into two general categories: Physical and Chemical.

1. Physical Properties

• Definition: Characteristics that can be measured or observed without changing the identity or chemical composition of the substance.
• Sub-classifications of Physical Properties:
  • Intensive Properties: These are properties that do not depend on the amount of matter present. They are dependent on the kind or quality of the material.
    • Examples: Texture, color, odor, hardness, density, boiling point, electrical conductivity, and solubility.
  • Extensive Properties: These properties depend entirely on the amount or quantity of matter present.
    • Examples: Volume, mass, length, and area.

2. Chemical Properties

• Definition: Characteristics that result in a change in the composition of the matter, leading to the production of a new substance.
• Examples: Flammability and reactivity.

In-Depth Physical Properties

• Color: Describes the physical appearance (visual) of a substance, such as the red color of an apple.
• Texture: Describes how a substance feels to the touch (e.g., smooth, hard, or rough).
• Mass: Refers to the total quantity of matter present in an object (e.g., $100\,g$ of meat).
• Volume: A measure of the amount of three-dimensional space occupied by an object. Units are typically cubed (e.g., $cm^3$, $m^3$).
  • Volume Formulas:
    • Cube: $V = s \times s \times s = s^3$
    • Rectangular Solid: $V = l \times w \times h$
    • Cylinder: $V = \pi r^2 h$
    • Sphere: $V = \frac{4}{3} \pi r^3$
  • Volume Calculation Example:
    • Given wood dimensions: Length = $9.3\,cm$, Width = $3.2\,cm$, Height = $1.3\,cm$.
    • Calculation: $V = 9.3\,cm \times 3.2\,cm \times 1.3\,cm = 38.688\,cm^3$
• Electrical Conductivity: A measure of how effectively electric currents move through a substance.
• Thermal Conductivity: The rate at which a substance transfers heat.
  • Example: Stirring coffee with a metal spoon. Heat transfers from the higher-temperature water to the lower-temperature spoon, causing the spoon to feel warm.
• Density: The measure of mass within a specific volume. It serves as a tool for identification (e.g., water has a density of $1\,g/cm^3$).
  • Formula: $D = \frac{Mass}{Volume}$
  • Density Calculation Example:
    • Given wood Mass = $57.61\,g$ and calculated Volume = $38.688\,cm^3$.
    • Calculation: $D = \frac{57.61\,g}{38.688\,cm^3} = 1.489\,g/cm^3$
• Solubility: The ability of a substance (solute) to dissolve in another substance (solvent).
  • Application: Solubility can be used to separate mixtures, such as sand and sugar, because sugar dissolves in water while sand does not.
• Malleability: The ability of a substance to be rolled or pounded into various shapes without breaking. Examples include aluminum, gold, and iron.
• Magnetic Attraction: Observed when a metal has the property of attracting another metal.

In-Depth Chemical Properties

• Definition: The ability of a substance to change its chemical composition to form a new substance.
• Flammability: The ability of a substance (like wood or paper) to burn.
• Reactivity: The ability of a substance to interact with another substance to form one or more new products.
  • Example (Rusting): Clean iron reacts with oxygen in moist air to form rust (iron (III) oxide).
  • Chemical Reaction for Rust: $4Fe + 3O_2 \rightarrow 2Fe_2O_3$

Comparative Examples of Physical and Chemical Changes

Questions & Discussion

• Riddle: "I am black when you buy me, red when you use me. When I turn white, you know it's time to throw me away. What am I?"
• Answer: Charcoal.
• Identification through Density: Activity 1 notes that different substances have different properties. Density values provided for reference include $1\,g/mL$ and $7.8\,g/mL$. Examples of volumes observed are $58.51\,mL$ and $154.93\,mL$.