Chapter 1: Matter & Measurements – Foundations of Chemistry

Chapter 1: Matter & Measurements

Introduction to Chemistry

Chemistry is the scientific study of matter, its properties, composition, structure, and the changes it undergoes during chemical reactions. Understanding the basic concepts of matter and its classification is fundamental to all areas of chemistry.

• Chemistry is the study of the composition, structure, properties, and reactions of matter.

• Matter is anything that has mass and occupies space.

• Examples of matter: air, water, soil, living organisms.

• Non-matter: forms of energy such as sunlight, heat, and sound.

Physical and Chemical Properties

Properties of matter are characteristics that help us identify and classify substances. These properties are divided into two main categories: physical and chemical.

• Physical properties: Characteristics that can be observed or measured without changing the substance's identity.

  • Examples: color, odor, melting point, boiling point, density, state of matter.

• Chemical properties: Characteristics that describe a substance's ability to undergo a specific chemical change.

  • Examples: flammability, reactivity with acids, ability to rust.

Physical and Chemical Changes

Changes in matter can be classified as physical or chemical, depending on whether the substance's identity is altered.

• Physical change: A change that does not alter the identity of a substance.

  • Examples: freezing, melting, dissolving, breaking, cutting.

• Chemical change: A change that results in the formation of one or more new substances with different properties.

  • Examples: burning, rusting, digestion, fermentation.

States of Matter

Matter exists in three primary physical states: solid, liquid, and gas. Each state has distinct characteristics regarding shape and volume.

• Solid:

  • Definite shape and definite volume.

  • Particles are closely packed in a fixed arrangement.

• Liquid:

  • Definite volume but no definite shape (takes the shape of its container).

  • Particles are close together but can move past one another.

• Gas:

  • No definite shape or volume (expands to fill its container).

  • Particles are far apart and move freely.

Changes of State:

• Melting: Solid to liquid

• Freezing: Liquid to solid

• Vaporization: Liquid to gas

• Condensation: Gas to liquid

• Sublimation: Solid to gas

• Deposition: Gas to solid

Additional info: The energy involved in these changes is discussed in more detail in later chapters.

Classification of Matter by Composition

Matter can be classified based on its composition as either a pure substance or a mixture.

• Pure Substance: Matter with a fixed composition and distinct properties.

  • Element: A substance that cannot be broken down into simpler substances by chemical means (e.g., oxygen, gold).

  • Compound: A substance composed of two or more elements chemically combined in fixed proportions (e.g., water, carbon dioxide).

• Mixture: A physical combination of two or more substances where each retains its own properties.

  • Homogeneous mixture (solution): Uniform composition throughout (e.g., salt water, air).

  • Heterogeneous mixture: Non-uniform composition; different parts are visible (e.g., oil & vinegar, pizza).

Type	Description	Examples
Element	Pure substance, cannot be broken down by chemical means	Oxygen (O2), Gold (Au)
Compound	Pure substance, composed of two or more elements chemically combined	Water (H2O), Carbon dioxide (CO2)
Homogeneous mixture	Uniform composition throughout	Salt water, air
Heterogeneous mixture	Non-uniform composition	Oil & vinegar, pizza

Expressing Chemical Change: Chemical Reactions

Chemical changes are represented by chemical equations, which show the reactants (starting substances) and products (new substances formed).

• Chemical reaction: A process in which one or more substances (reactants) are converted into one or more new substances (products).

• Example: Electrolysis of water

$\text{2 H}_2\text{O} (l) \rightarrow 2 \text{H}_2 (g) + \text{O}_2 (g)$

Additional info: Chemical reactions will be discussed in more detail in Chapters 5-7.

The Elements of the Periodic Table

The periodic table organizes all known elements according to their atomic number, electron configuration, and recurring chemical properties. Elements are the building blocks of all matter.

• Each element is represented by a unique symbol (e.g., H for hydrogen, O for oxygen).

• Elements are arranged in rows (periods) and columns (groups or families) with similar properties.

Additional info: The periodic table will be explored in detail in Chapter 2.