Chapter One: Matter and Life – Introduction to Chemistry, Matter, and the Elements

Chapter One: Matter and Life

What is Chemistry and Why is it Important?

Chemistry is the scientific study of matter and the changes it undergoes. It is a central science that helps us understand the composition, structure, and properties of substances, as well as the energy changes that accompany chemical processes.

• Matter is anything that occupies space and has mass.

• Chemistry is fundamental to understanding the natural world, including biological processes, environmental phenomena, and technological advancements.

• Both natural chemicals (e.g., those found in plants and animals) and synthetic chemicals (e.g., plastics, pharmaceuticals) are studied in chemistry.

Example: The study of ibuprofen, a synthetic pharmaceutical, involves understanding its chemical structure and how it interacts with biological systems.

Relationships Between Chemistry and Other Disciplines

Chemistry is interconnected with many scientific fields. It provides foundational knowledge for biology, physics, environmental science, geology, medicine, and more.

• Biology: Cell biology, genetics, physiology

• Biochemistry: Molecular biology, endocrinology

• Medicine and Allied Health Sciences: Pharmacology, nutrition, radiology

• Environmental Science: Ecology, pollution studies

• Physics: Atomic and nuclear physics, spectroscopy

• Geology, Astronomy, Nuclear Chemistry

Additional info: Chemistry is often called the "central science" because it bridges physical and life sciences.

Introduction to Matter and the Elements

States of Matter

Matter exists in three primary states: solid, liquid, and gas. Each state has distinct physical properties.

• Solid: Definite shape and volume. Particles are closely packed in a fixed arrangement.

• Liquid: Definite volume but takes the shape of its container. Particles are close but can move past one another.

• Gas: Neither definite shape nor volume. Particles are far apart and move freely.

Example: Water can exist as ice (solid), liquid water, or steam (gas).

Properties of Matter

Matter is characterized by its physical and chemical properties.

• Physical Properties: Can be observed without changing the substance's chemical identity (e.g., density, color, melting point).

• Chemical Properties: Describe how a substance interacts with other substances, resulting in a change in chemical composition (e.g., reactivity with water, flammability).

Physical and Chemical Changes

Matter can undergo physical or chemical changes.

• Physical Change: Alters the form or appearance but not the chemical composition (e.g., melting ice, boiling water).

• Chemical Change (Chemical Reaction): Alters the chemical composition, forming new substances (e.g., burning wood, rusting iron).

Example: Melting ice is a physical change; burning wood is a chemical change.

Classification of Matter

Matter can be classified as mixtures or pure substances.

• Mixture: A blend of two or more substances, each retaining its own properties. Can be separated by physical means (e.g., sugar dissolved in water).

• Pure Substance: Has a uniform and definite composition. Can be an element or a compound.

Classification Table

Type	Description	Example
Element	Cannot be broken down chemically; listed on the periodic table	Oxygen (O2), Gold (Au)
Compound	Can be broken down into elements by chemical means; composed of two or more elements	Water (H2O), Sugar (C12H22O11)
Mixture	Physical blend of substances; can be separated physically	Sugar water, air

The Periodic Table of Elements

The periodic table organizes all known elements by increasing atomic number and similar properties.

• Group (Family): Vertical column; elements in a group have similar chemical properties.

• Period: Horizontal row.

• Elements are classified as metals, nonmetals, or metalloids.

Classification of Elements

Type	Properties	Examples
Metals	Shiny, good conductors, malleable, ductile, mostly solids	Gold (Au), Copper (Cu), Zinc (Zn)
Nonmetals	Poor conductors, can be gases, liquids, or solids	Nitrogen (N2), Sulfur (S), Iodine (I2), Bromine (Br2)
Metalloids	Properties intermediate between metals and nonmetals; semiconductors	Boron (B), Silicon (Si)

Chemical Symbols and Formulas

Each element is represented by a unique chemical symbol, usually one or two letters (e.g., H for hydrogen, Na for sodium). Chemical formulas use these symbols and subscripts to indicate the number of atoms of each element in a compound.

• Chemical Formula: Notation showing the elements and the number of atoms (e.g., H2O, C6H12O6).

• If no subscript is shown, one atom is implied.

Example: The formula for water is H2O, indicating two hydrogen atoms and one oxygen atom per molecule.

Macroscopic and Microscopic Worlds in Chemistry

Chemists study matter at both the macroscopic (visible) and microscopic (atomic/molecular) levels.

• Macroscopic: Properties and changes observable with the naked eye (e.g., a chunk of copper metal).

• Microscopic: Atoms and molecules, which require models or instruments to study (e.g., the structure of a copper atom).

Atoms, Molecules, and Compounds

Atom: The smallest unit of an element that retains its chemical properties.

Molecule: Two or more atoms held together by covalent bonds; the smallest unit of a compound or element that retains its properties.

• Some elements exist as diatomic molecules (e.g., O2, N2).

• Molecular Compounds: Formed when nonmetals combine (e.g., H2O).

• Ionic Compounds: Formed when metals combine with nonmetals (e.g., NaCl).

Chemical Reactions and Equations

Chemical reactions involve the transformation of reactants into products, often represented by chemical equations.

• Reactants: Starting materials in a chemical reaction.

• Products: Substances formed as a result of the reaction.

• The arrow ($\rightarrow$) means "to form" or "yields".

Example of a Chemical Equation:

$\mathrm{Ni} + 2\mathrm{HCl} \rightarrow \mathrm{NiCl}_2 + \mathrm{H}_2$

This equation shows nickel reacting with hydrochloric acid to form nickel(II) chloride and hydrogen gas.