Matter & Energy

Classification of Matter

Matter is anything that has mass and occupies space. It can be classified into pure substances and mixtures, which are further divided as follows:

• Pure Substances: Elements and compounds with a fixed composition.

• Mixtures: Physical combinations of two or more substances. Mixtures can be:

  • Homogeneous Mixtures: Uniform composition throughout (e.g., solutions).

  • Heterogeneous Mixtures: Non-uniform composition (e.g., sand in water).

Examples: Sodium chloride (NaCl) is a compound; air is a homogeneous mixture; granite is a heterogeneous mixture.

States of Matter

Matter exists in three primary states: solids, liquids, and gases. Each state has distinct physical and chemical properties.

• Solids: Definite shape and volume; particles are closely packed.

• Liquids: Definite volume but no definite shape; particles are less tightly packed than in solids.

• Gases: No definite shape or volume; particles are far apart and move freely.

Physical vs. Chemical Changes:

• Physical Change: Change in state or appearance without altering composition (e.g., melting ice).

• Chemical Change: Change that produces new substances (e.g., rusting iron).

Changes of State

Changes between states of matter include:

• Freezing: Liquid to solid

• Melting: Solid to liquid

• Boiling: Liquid to gas

• Condensation: Gas to liquid

• Evaporation: Liquid to gas (at surface)

• Sublimation: Solid to gas

• Deposition: Gas to solid

Energy in Chemistry

Energy is the capacity to do work or produce heat. In chemistry, energy changes accompany physical and chemical changes.

• Specific Heat: The amount of heat required to raise the temperature of one gram of a substance by one degree Celsius.

• Equation:

• q: Heat energy (Joules)

• m: Mass (grams)

• c: Specific heat (J/g°C)

• ΔT: Change in temperature (°C)

Heating/Cooling Curve: A graph showing temperature change as a substance is heated or cooled, indicating phase changes.

Elements & The Periodic Table

Element Names and Symbols

Each element has a unique name and chemical symbol. Correct spelling and symbol usage are essential in chemistry.

Periodic Table Organization

The Periodic Table arranges elements by increasing atomic number and groups elements with similar properties.

• Periods: Horizontal rows

• Groups: Vertical columns

• Metals: Good conductors, malleable, shiny

• Nonmetals: Poor conductors, brittle, dull

• Metalloids: Properties intermediate between metals and nonmetals

Example: Sodium (Na) is a metal; chlorine (Cl) is a nonmetal; silicon (Si) is a metalloid.

Atoms & Electron Energy

Atomic Theory

Atomic theory describes the structure and behavior of atoms, the fundamental units of matter.

• Atom: Smallest unit of an element retaining its properties

• Subatomic Particles: Protons (positive), neutrons (neutral), electrons (negative)

Atomic Number: Number of protons in the nucleus

Mass Number: Sum of protons and neutrons

Atomic Mass: Weighted average mass of all isotopes of an element

Equation:

Electron Configuration

Electrons are arranged in shells, subshells, and orbitals around the nucleus. The arrangement determines chemical properties.

• Shells: Principal energy levels (n = 1, 2, 3...)

• Subshells: s, p, d, f types within shells

• Orbitals: Regions of space where electrons are likely to be found

Example: The electron configuration of carbon (C) is 1s2 2s2 2p2.

Periodic Trends

Periodic trends describe how properties of elements change across the Periodic Table.

• Atomic Size: Generally decreases across a period, increases down a group

• Ionization Energy: Energy required to remove an electron; increases across a period, decreases down a group

• Metallic Character: Increases down a group, decreases across a period

Lab: Elements

Lab Applications

Laboratory activities may include identifying elements, measuring physical properties, and observing chemical changes.

• Element Identification: Use chemical symbols and correct spelling

• Physical and Chemical Properties: Observe and record changes during experiments

Summary Table: Key Concepts

Additional info: This study guide is based on the test outline and content coverage for a GOB Chemistry college course, including matter and energy, elements and the periodic table, atomic structure, and laboratory skills. Students should be familiar with the listed elements and their symbols, as well as key concepts in atomic theory and periodic trends. Calculations involving specific heat and atomic mass are also included.